The First Mammals

The earliest known fossil record of mammals has been dated to about 160 million years ago.18 By 140 million years ago, our mammalian ancestors were evolving jaws with high flanges at the back of the jaw and larger jaw muscles connecting the jaw to the skull, permitting a more forceful bite. In time, to further the business of getting to and acquiring food, and of avoiding predators, limb bones elongated or shortened and toes adapted with claws, nails and feet. Some adapted for speed, others for climbing, and others with hoofs were suited for grazing. Grazing limbs lost their ability to turn to the side and found two primary toes (cloven hoofs) well suited to the task of escaping predators. Other limbs adapted for swimming, climbing, running, digging, walking, flying and seizing. All of these adaptations placed new survival demands on the brain for speed and information processing. Relative to body weight, a larger brain began to evolve that could process large volumes of information from the senses and provide fine muscular control.

By 120 million years ago, Africa and South America separated as did Eurasia and North America. The Atlantic Ocean was in its infancy as a rift valley, and by about 70 million years ago our mammalian ancestors probably weighed about 150 grams, had long tails, a body length of about seven inches, walked on all fours, had long snouts and ate fruit and insects. Among the animals that shared their environment were dinosaurs, but this would change. 

 

By 90 million years ago conifer-eating dinosaurs were forced to regions where colder temperatures gave conifers an advantage over flowering plants. The cycle was now complete. Those dinosaurs whose success followed the success of conifers over tree ferns were now experiencing hardship as conifers lost ground to flowering plants. It’s ironic that the fate of many awesome dinosaurs would be affected so profoundly by the evolution of fragile flowers. Triceratops, a dinosaur with a large head plate and three horns, was an exception. It was able to eat flowering plants and survived in great herds until about 65 million years ago. At that time, the Cretaceous period ended. A meteor about six miles across, traveling at about 50,000 miles per hour struck at a location that we know today as the town of Chicxulub in Mexico’s Yucatan peninsula. Its energy was equivalent to about 6.6 billion Hiroshima bombs. Although the crater ultimately reached about 120 miles in diameter, computer simulations indicate that within ten seconds after impact the crater was already 30 miles across, 15 miles deep, and was spewing molten rock in ballistic trajectories all over Earth. The impact fractured the Earth’s crust and created earthquakes and tsunamis. The sky was filled with molten ejecta and fires started everywhere. The vast quantity of limestone and sulfur19 in the impact area released vast quantities of carbon dioxide and sulfur dioxide into the atmosphere. This was doubly unfortunate. The first result was that sulfur dioxide combined with atmospheric moisture to form sulfuric acid droplets. Such droplets block sunlight, cool the Earth and cause acid rain possibly as strong as battery acid. Present day volcanic studies indicate that the sulfur dioxide might have cooled the Earth as much as 10 degrees Celsius for a decade. Subsequently, carbon dioxide released by the impacted limestone could have caused the atmosphere to warm as much as 15 degrees Celsius for centuries.

 

From computer simulations and various evidence, we now know that the Chicxulub impact in the Yucatan caused a wave over one mile high to sweep over what is now Cuba, and a layer of sea floor rubble about three feet deep to cover parts of Texas. Ocean bed core samples taken 320 kilometers east of Jacksonville, Florida recorded the event. Prior to impact, the core sediments were rich in fossil remains, characteristic of a healthy ocean ecosystem. Deposited on top of that layer is about ten centimeters of gray-green impact debris topped by a thin red layer rich in iron, indicating that the meteor probably contained iron since the Yucatan site had little iron. On top of the red layer is about five centimeters of sediment with no evidence of fossils. It’s estimated that this layer took 5,000 years to deposit. Sediments above the five centimeter layer show the return of fossils and evidence that the ocean near Florida had reestablished an ecosystem.20 Virtually everywhere on land a layer of iridium containing soot about 1/2 inch thick marks the end of the Cretaceous period. Iridium is an element uncommon on Earth’s surface, but commonly found in meteors. In the late 1970’s the dark layer of iridium covering Cretaceous period soil led Luis and Walter Alvarez to unlock the mystery of how the Cretaceous period ended.21

 

It’s estimated that six million years before the Chicxulub impact there were about 60 kinds of dinosaurs. That number dropped to less than 20 by about 2 million years before the impact. About 90 percent of Earth’s biomass burned in the impact fires, and some believe that the remaining dinosaurs eventually starved. Of the other species then on Earth, about two-thirds were destroyed. Whether the demise of dinosaurs was due solely to an “impact winter” is not clearly understood. It’s said that some dinosaur species survived the impact and later became extinct for other reasons. What is clear is that their demise changed the status of our mammalian ancestors from dinosaur snacks to precursors of apes that would dominate the Earth. Food scarcity resulting from the post impact blockage of sunlight devastated animals directly or indirectly dependent on fresh vegetation. However, insects survived on the remains of decomposing plants and, at that time, our ancestors ate insects.

 

When the meteor struck, North and South America were not yet joined at what we call Panama, and where the Mediterranean would be formed was open water from the Atlantic to the Pacific. By about 50 million years ago our ancestral mammals’ limbs had grown longer, their snouts had become shorter, they lived in trees, developed protruding ears, weighed about 300 grams (about 10 ounces), and had long tails. Small though they were, their tiny neocortices were providing them with enhanced mental capabilities well suited to ensure their survival in a meteor-altered world. The dinosaurs as such were gone and tapir-like mammals weighing about 200 pounds was among the animals that shared our ancestor’s habitat.

 

About 55 million years ago, when the Himalayan Mountains formed as present-day India collided with Asia, huge limestone formations were exposed to the weather. As carbon dioxide in the atmosphere combines with rain it forms carbonic acid. Although weak, carbonic acidic rain would have reacted with the exposed limestone of the Himalayas to form carbonate particulates, trapping atmospheric carbon and washing it into the sea. It’s thought by some that a reduction in atmospheric carbon dioxide by this means contributed to global cooling and might have precipitated relatively recent glaciation cycles, of which there have been about 12 in the past 20 million years. 

 

Between 40 and 20 million years ago, the Mediterranean was formed as Africa collided with Eurasia. Salt domes found at the bottom of the Mediterranean, deep cuts in the rock at the bottom of the Nile and other rivers feeding the Mediterranean, and other evidence suggests that the Mediterranean went dry. Rivers flowing into the Mediterranean didn’t, and still don’t provide enough water to equal its evaporation rate, and it gradually went dry. About five million years ago the Gibraltar Strait was formed where the Atlantic cut a channel to the Mediterranean. Lighter, less salty water from the Atlantic now flows in at the upper portion of the Strait, and heavier evaporation-concentrated saltier water flows out in the lower portion. Phoenician sailors discovered these currents and lowered drag devices into the lower out-flowing water to pull their ships against the surface current into the Atlantic. 

 

By about 30 million years ago, our ancestors looked monkey-like, weighed about 7 kilograms (about 15 pounds), had 32 teeth as do we, were arboreal and ate fruit. They coexisted with a herbivore that looked like a rhinoceros with side-by-side horns. By 17 million years ago, they evolved a chimp-like appearance and weighed about 18 to 50 kilograms. They were apes with no tails, a more substantial jaw, shortened faces, rounded skulls that were rotated to look forward while standing, but with an unimpressive brain size. An elephant-like mammal was among the animals that shared their environment. A large mammal with a horse-like head and gorilla like legs was among the animals that shared our primate ancestor’s environment 14 million years ago. This ancestor began to stand on its pelvic limbs and was functioning with a neocortex that was increasingly sharing decision-making with the older amygdala and hippocampus. By 4 million years ago, our hominid ancestors had shortened arms, could walk with a waddle, and had a brain slightly larger than a chimpanzee’s. Lucy is the name given to fossil remains of one of these Australopithecus Afarensis ancestors found in Ethiopia. By 3.5 million years ago, hominins left their footprints in the volcanic ash of present day Tanzania. 

 

About three to ten million years ago North and South America were joined with the formation of present day Panama. It’s theorized that this formation cut off warm ocean currents that flowed to the Arctic. Similarly, flow through what is now the Bering Strait was reduced as North America moved closer to Asia. Over about 300 million years, the internal dynamics of Earth had moved the continents by plate tectonics from an essentially north-south mass concentrated mostly in the southern hemisphere to a distributed east-west arrangement centered closer to the equator. In addition to influencing biological evolution in other ways, it’s thought that this massive reforming of the continents resulted in the restriction of warm currents flowing to the Arctic and might have contributed to recent periodic glaciations. 

 

By two million years ago Homo Habilis (handy man) were probably the first recognizable humans. Weighing about 40 kilograms (88 pounds) with an upright stance, they were about four feet tall, had a brain about half the size of ours and were able to make tools. Recent research indicates that humans evolved lower levels of testosterone, which, compared with chimps, made our ancestors less aggressive, more cooperative, not as strong and more inclined to rounded facial features compared with chimps. 

 

By 1.7 million years ago Homo Erectus (the standing human) had a less massive jaw and a much larger brain (from 900 to 1000 cubic centimeters). Homo erectus built shelters, made flint tools and hunted and gathered food. By 1 million years ago Homo Erectus were able to live in previously uninhabitable territory because they were able to make fire. By 800,000 years ago up to five people left a series of footprints in mud on the bank of an ancient river estuary on what is now the English shore.

 

Homo Sapiens Archaic lived 200 to 100 thousand years ago. They looked like stocky humans, weighed about 50 to 70 kilograms (110 to 154 pounds), and some lived in caves and as hunting nomads. Some contended with cave hyenas, which were much larger than their present-day relatives. By 35 thousand years ago, some Homo Sapien Sapiens (the thinking human) lived in tents made of wood or bone frames covered with animal hides. Isolated groups had evolved characteristics suited to their environments. Long noses, skin with varying degrees of pigmentation and flat noses were a few of the obvious adaptations. They organized, tanned hides, made flint and reindeer-antler tools, created cave and rock paintings, buried their dead and apparently believed in the existence of a spirit world. And most importantly, they thought with the same conflicted brain we inherited.

 

Large-scale Social Evolution Begins

The first coming together of scattered Western settlements occurred in the Middle East. Why in this region? Perhaps the following happened. In a process similar to the drying of the Mediterranean, it’s thought that glaciation lowered sea levels caused the Black Sea to become a brackish-water lake dammed off from the Mediterranean at what is now the Bosporus strait in Turkey. About 8,200 years ago, the enormous glacial lake Agassiz in North America suddenly emptied into Hudson Bay and the Atlantic Ocean. The resulting rise in sea level inundated the land bridge between Britton and Continental Eurasia and as the Mediterranean Sea rose, water flowed across what is now the Bosporus Strait into the Black Sea, where the water level rose about 270 feet.  Today, saline water from the Mediterranean flows into the Black Sea at the Bosporus Strait, which is about 20 miles long and 1/2 mile wide at its narrowest. 

Before the Black Sea flooded, it’s inflow of water was from the Danube, Kuban, and other rivers. The inflow flooded what is believed to have been an inhabited region of considerable size, especially in the north western part of the present Black Sea. Pre-flood inhabitants would have been forced to higher ground during the time it took to bring the Black Sea to its present level. Based on discoveries of submerged pre-flood shorelines and related findings, some scientists believe that the cataclysm might be the source of Middle Eastern myths involving disastrous floods.22

If a pre-Sumerian population lived on the shores and in the marshes of a pre-flood Black Sea, they would have been displaced and traumatized by the deluge. Water could have risen more than nine inches per day, on average, and completely flooded the region within about 12 months. In their common plight, people from small scattered settlements could have combined and built large villages or cities away from the rising sea. Such a process would have been contemporaneous with the appearance of “city-kings” in the history of the region. If events occurred in this way, pre-Sumerians who migrated south through the high ground of the Turkish mountains and into the fertile crescent of the Tigris-Euphrates region would have built their cities in what is present-day Iraq, where cities dating to about 5,000 BCE have been found. Such a traumatic flood would have been recorded in the oral history of the survivors, and stories about the flood would have filtered through many generations, and might be the source of the sages’ description of the great flood in the Sumerian story of Gilgamesh. The Sumerians believed the flood to be retribution for the sin of an ancient Sumerian king,23 Apparently, the same story was subsequently reinterpreted by the Babylonian and Hebrew cultures, and in turn became part of the Christian tradition involving Noah. Recent research suggests that the Persian Gulf also flooded about 8,200 BCE. 

 

By 5,000 BCE Sumerians in the Fertile Crescent were evolving language, writing, technology, and social organization. They created social hierarchies, irrigation farming, currency, law, sophisticated scripts, libraries, schools, literature, poetry, cosmetics, jewelry, sculpture, palaces, temples, arches, columns, slavery, and ecclesiasticism.24 Evidence of similar, contemporaneous cultural evolution has been found in Indus culture. 

 

After billions of years of accumulating molecular knowledge in the form of evolving DNA, self-organizing knowledge had crossed a threshold with the Sumerian, Indus and other civilizations of that time. From a reflexive emotional brain suited for survival in a hostile environment, trial and error evolution had produced a thinking organ capable of evolving knowledge in the form of organized understanding and beliefs, instead of organized nucleotides. A few millennia later, the Axial Age invented natural philosophy, employing a rational thought process to organize knowledge and belief systems. In just over two millennia following the death of Aristotle, that process evolved into a scientific method of analysis that has enabled us to discover the history of life on Earth and to begin understanding the biology of belief. After eons of evolving organic life by refining DNA using Nature’s test of survival value, the process of self-organizing knowledge began to evolve human culture and wisdom by refining human beliefs, not by selecting for their survival value, but by selecting based on their perceived value to those who would acquire them.

 

Copyright 2019 Research Associates, LLC

 

Brain Evolution Endnotes

1.    Lucretius, Vol. 3, IV, page 834, quoted in Durant, Will, The Story of Civilization, 1944, Vol. 3, Bk. 2, Ch. 8, Sec. 2, Par. 15. 

2.    Lucretius, Vol. 3, V, page 419, quoted in Durant, Will, The Story of Civilization, 1944, Vol. 3, Bk. 2, Ch. 8, Sec. 2, Par. 15. 

3.    Lucretius, Vol. 3, V, Page 837, quoted in Durant, Will, The Story of Civilization, 1944, Vol. 3, Bk. 2, Ch. 8, Sec. 2, Par. 15.

4.    Bakewell, C., Sourcebook in Ancient Philosophy, 1909, New York, p. 6, referenced in Durant, Will, The Story of Civilization, 1939,
       Vol. 2, Bk.  2, Ch. 6, Sec. 14, Part 1, Par. 14.

5.    Zimmer, Carl, “Life Takes Backbone,” in Discovery Magazine, December, 1995, p. 38-9.

6.    “Origin of Life on the Earth,” in Scientific American, October, 1994, pp. 77-83.

7.    de Duve, Christian, “ The Birth of Complex Cells,” in Scientific American, April, 1996, pp. 50-57.

8.    Travis, John, “How many genes does a bacterium need?” in Science News, September 28, 1996, Vol. 150, No. 13, p. 198.

9.    Lipkin, R., “Early life: In the soup or on the rocks?” in Science News, May 4, 1996, Vol. 149, No. 18, p. 278.

10.  Fackelmann, Kathleen, “The Cortisol Connection,” in Science News, November 29, 1997, Vol. 152, No. 22, p. 350.

11.  “The Slime Alternative,” in Discover Magazine, September, 1998, pp. 86-93.

12.  “The Origin of Species,” in The Economist, November 25, 1995, pp. 85-87.

13.  Nusslein-Volhard, Christianne, “Gradients That Organize Embryo Development,” in Scientific American, August, 1996, pp. 54-55, 58-60.

14.  Travis, John, “The Ghost of Geoffroy Saint—Hilaire,” in Science News, September 30, 1995, Vol. 148, No. 14, pp. 216-8.

15.  Monastersky, Richard, “Jump—Start for the Vertebrates,” in Science News, February 3, 1996, Vol. 149, No. 5, pp. 74-7.

16.  Zimmer, Carl, “Breathe Before You Bite,” in Discover Magazine, March, 1996, p. 34.

17.  Travis, John, “Yeast genetic blueprint publicly unveiled,” in Science News, May 4, 1996, Vol. 149, No. 18, pp. 278-278.

18.  Pennisi, E., “Mice, Flies Share Memory Molecule,” in Science News, October 15, 1994, Vol. 146, p. 244.

19.  “Repeating DNA surprises once again,” in Science News, March 16, 1996, Vol. 149, No. 11, p. 171.

20.   Travis, John, “Let’s repeat: Mutation gums up brain cells,” in Science News, December 20/27, 1997, Vol. 152, No. 25/26, p. 390.

21.   Travis, John, “Repeating DNA linked to schizophrenia,” in Science News, December 8, 1997, Vol. 152, No. 19, p. 294.

22.  “How brain cells make up their minds,” in Science News, October 28, 1995, Vol. 148, No. 18, p. 284.

23.  “Mind Forming,” in The Economist, July 15, 1995, p. 63.

24.  “Anatomy of the Human Nervous System,” The Encyclopedia Britannica, Multimedia Disc, 1994-1998, Encyclopedia Britannica Inc.

25.   Begley, Sharon, “Your Child’s Brain,” in Newsweek Magazine, February 19, 1996, pp. 55-62.

 

 

Essay 2

Creation According to Science

 

The Early Universe

Inasmuch as we might never know what happened before the Big Bang, if, indeed, anything happened, the story of creation begins about 13.8 billion years ago (plus or minus a few hundred million years) when it is thought that all of the mass and energy of the universe occupied an extraordinarily small volume that began to expand. When it reached the size of our solar system, protons, neutrons, and electrons formed as more fundamental subatomic particles began to cool. By the time the universe was about 1,000 times the size of our solar system, neutrons and protons formed nuclei of hydrogen, helium, deuterium, and lithium. The universe was now about three seconds old. It was too hot to be transparent or to permit newly formed atomic nuclei to capture electrons to form atoms. That would take another 300,000 years. And when the universe had cooled enough to form atoms, over time they combined under the influence of gravity to form stars.1 When the universe was less than a billion years old, an entire generation of stars had formed and died, and massive galaxies came together.2

 

How did atoms such as helium and iron form? When a spinning disk of matter collapses under its own gravity into what will become a star, the intense pressure and temperature at its core, causing hydrogen to fuse into helium. The process is the same as that of an exploding hydrogen bomb, but on an enormous scale. The continuous flow of energy given off by this ongoing hydrogen fusion limits the degree of collapse of the new sun’s core. Eventually, when virtually all the sun’s hydrogen is converted to helium, the core shrinks until there is sufficient temperature and pressure to fuse helium to create carbon. This process of creating successively heavier atoms continues until iron is formed. Unlike lighter atoms, iron does not give off energy when it fuses; it consumes energy. So nuclear burning stops with iron, and gravity collapses the sun’s core.

 

Large stars reach the carbon stage more quickly than do small stars. Medium size stars such as our sun (of which we are aware of about 100 billion billion), the iron stage is reached in about 10 billion years. Stars smaller than our sun can burn for very much longer. In stars with a mass about 20 times that of our sun, fusion is more rapid and iron is formed in about 10 million years. Stars such as our sun gradually brighten as they convert hydrogen into helium. In its infancy, our sun was about 70 percent its present brightness. Over the next billion years our sun will increase in brightness by about 10 percent, perhaps enough to vaporize our oceans.3 By about 6.5 billion years from now, the sun’s luminosity will about double. At that time hydrogen at the sun’s core will be depleted, but hydrogen in the shell of gas surrounding the core will continue to fuse into helium. This will cause the sun’s outer layers to expand, cool, and appear redder. Our sun will have metamorphosed into what is called a “red giant.” This phase will take over a billion years, during which the sun will expand to well beyond the orbit of mercury. As helium begins to fuse into carbon in the core, the sun will begin to shrink. It will take about 100 million years to consume the remaining helium in its core. When helium in the core has been consumed, helium in a gas shell surrounding the core will ignite. This consumed helium core surrounded by newly ignited helium gas will be enclosed in a shell of burning hydrogen. As the core contracts, it will draw in the two burning shells. The helium gas shell will experience a series of explosions, which will begin a final brightening and expansion of the sun that will last for about 20 million years. During this phase the sun will increase its diameter to beyond Earth’s present orbit. Although the Earth will have long since lost its biosphere, the enormous loss of mass experienced by the sun during its later years will reduce its capacity to hold Earth in its present tight orbit. It’s thought that the resultant increase in the size of Earth’s orbit might keep it from being engulfed by the expanding sun. Over the following few million years, the sun’s outer layers will dissipate and reveal its smoldering core. Unlike the dense cores of neutron stars formed when larger stars reach the end of their cycle, the sun’s core will not collapse beyond the density permitted by electron repulsion of its core atoms. Its smoldering remnant will have become what is called a “white dwarf,” perhaps to be orbited by Earth until the next cataclysm.4

 

Why do some stars explode and where do black holes come from? Stars about 20 times more massive than our sun experience a very different end. When such stars reach the iron stage, gravitation in the star’s iron core is so intense that the core collapses. Unlike smaller stars, the mass of iron in the core of large stars is sufficient to compress the nuclei of iron atoms together. Electron repulsion is completely overcome. The collapse takes just a second. If enough material is present to create gravity so intense that light cannot escape, a black hole is formed. If less material is present, a neutron star is formed instead. An explosion following collapse blows the outer stellar material into space and releases the equivalent of all the energy released by our sun in its lifetime. It is as bright as a billion suns. Such an exploding star is called a “type II supernova,” and appears as a bright spot in the night sky lasting a few weeks. In 1054 Chinese astronomers observed such a bright spot in the night sky. It was the supernova that produced what we now call the Crab nebula. A more recent supernova was observed in February of 1987.

 

How does a supernova explosion create heavy atoms? The shock waves of supernovae create heavier elements such as uranium, lead, gold, and radioactive material, which accounts for the rarity of these heavy atoms. In this way, beginning with hydrogen, stars have manufactured most of the material from which planets are made.5 The initial expansion or Big Bang left the universe a glowing, opaque fireball. As it cooled, stars were speeding away from each other in the expanding universe. Not long after that, large stars began exploding—sending debris in every direction.6 It must have looked like slow motion fireworks. During supernovi, oxygen, nitrogen, and carbon were ejected into space at high speed and collided with slow—moving protons. The collisions formed lithium, beryllium, and boron.

 

How are water and other compounds formed? In the gas clouds between stars, conditions are right for the formation of molecules such as hydrogen gas, water, carbon monoxide, ammonia, alkanes (methane series), polycyclic aromatic hydrocarbons (naphthalene), acetylene, and glycine (an amino acid).7 In a 1993 experiment, hydrogen gas and naphthalene were exposed to a 9,400 volts electrical discharge. An infrared spectrum analysis of the yellow-brown residue produced by the discharge revealed a close resemblance to a similar analysis of the Murchison meteorite that fell to Earth in Australia in 1969. It’s thought that ionized hydrogen exposed to intense stellar outbursts would create conditions similar to those in the high-voltage experiment. More than 100 chemicals have been detected in interstellar clouds.8 Burning and exploding stars and interstellar synthesis are the primary processes by which hydrogen is converted into the heavier elements and compounds. It’s thought that as solar systems formed within galaxies, stellar radiation modified interstellar chemicals to form ethane from acetylene, for example.9,10 Many of the hydrocarbon compounds created by these processes are common building blocks of life as we know it. If autogenesis or self-organizing molecular life required the presence of such compounds, lightning storms in Earth’s early atmosphere (simulated in the 1993 experiment) might have produced the required compounds, perhaps making the interstellar contribution unnecessary. 

 

How do galaxies and solar systems form? The cloud of dust and debris left after a massive star explodes is called a “nebula.” In time, matter in nebulae condenses into spinning disks of stars, gas, debris, ice, and dust. Each such spinning disk is a galaxy that can take the shape of a pinwheel or a flat disk with a bulge at its center. It’s thought that at least some galaxies have black holes at their centers. A black hole is an object so massive that the velocity needed to escape its gravity exceeds the speed of light, in which case we can’t see it directly because light that might emanate from or reflect off it cannot escape its gravity. The disk shape of galaxies is attributed to the spin plane of matter at the center of the disk. Each star in a galaxy is the center of its own spinning disk of matter, which might include planets and rings of debris such as our asteroid belt, all aligned roughly in the spin plane of the star. In turn, each planet could be the center of its own system of moons or rings. Moons, in turn, are capable of capturing and orbiting objects, a fact on which we relied in planning the 1969 moon landing. Even asteroids have been found to have tiny moons.11

 

The first galaxies formed about one billion years after the Big Bang, and incorporated stellar remnants and interstellar compounds. Recent observations of the cosmos indicate that there are in excess of 100 billion galaxies distributed along the boundaries of spherical voids, like the film on connected soap bubbles.12 The voids measure in the hundreds of millions of light years across.13

 

Our galaxy began to form about 10 billion years after the Big Bang, and our star (the sun) is near the outer edge of the galaxy. When we look at the night sky we see an edge view of hundreds of millions of stars that make up our galaxy. Their number and density appear as a band of white we call the Milky Way. Calculations indicate that there is a black hole of about 4.6 million solar masses at the center of our galaxy. The radiation associated with matter being drawn into such a black hole is thought to be obscured in the visual spectrum by a vast dust cloud between Earth and our galaxy’s black hole.

 

Our Star

How did our planets form and why does Earth continue to be bombarded by meteors and other significant objects as recently as perhaps 13,000 years ago? Our solar system, comprising our star, the Earth, other planets and orbiting material, formed about 4.7 billion years ago from a collapsing cloud of dust, gas, ice, and debris. A simplified description of the process is that as the cloud collapsed in on itself, it began to spin faster and faster, like a skater bringing her arms closer to her body to spin faster. The collapsing cloud was a chaotic affair influenced primarily by gravity, electromagnetism, and inertia.14 German astronomer and mathematician Johannes Kepler (1571-1630) determined that objects travel around the sun in elliptical orbits. Some objects orbited in nearly circular paths while the orbits of others were acutely elliptical and not necessarily coplanar—a combination that generated collisions of all kinds. In time, random agglomerations of matter attracted and held more and more gas, dust, and debris that came into the vicinity of their orbits. Debris was relentlessly assembled into planets. Some inchoate planets had molten cores, heated in part by nuclear fission. Eventually the forming planets accumulated enough mass for gravity to crush them into spheres. Some planets were struck by large planetesimals. Such impacts were capable of knocking small, loosely assembled planets to pieces. However, the collective gravity of such a fragmented planet could reassemble the planet in time. Of the material thrown up from such impacts, some would fall back and some would escape the planet’s gravity, never to return. And, if the impact were a glancing blow, a moon could be created from material that neither fell back nor escaped but which was thrust into orbit around the planet. Jupiter, Neptune, Saturn, and Uranus were large enough to capture hydrogen and helium gas in great quantities.

 

When the temperature and pressure reached critical levels inside the ball of hydrogen at the center of the sunless system, hydrogen began to fuse into helium and began emitting energy. The sun began to glow and to eject particles (solar wind) that swept orbiting dust beyond the outer reaches of the system. Without obscuring dust, the sun’s light revealed a new solar system. During the more than 500 million years this process that took to complete, Earth and the other planets settled into a reasonably stable relationship with the sun and each other. However, not all of the smaller orbiting bodies were as stable. Still orbiting the sun is debris that was not captured during the formation of the solar system. Some of it travels in Earth-crossing orbits. We know this debris as asteroids, comets, and meteors. Comets consist chiefly of ammonia, methane, carbon dioxide, and water, and it’s thought that an orbiting collection of potential Earth-crossing comets resides beyond the orbit of Neptune to far beyond Pluto. It’s possible that sun-orbiting comets exist as far out as 50 times the distance from the Earth to the sun—about a fifth of the distance to Alpha Centauri (the star nearest to our solar system). Comets very far from the sun could have their orbits disturbed by passing stars or other matter, and could enter the inner solar system.15 Military defense systems intended to protect against surprise missile attack regularly recorded upper atmosphere impacts by comets of a few meters in diameter. The impacts average about one per month and their energy is equivalent to about 1/15th the energy of the Hiroshima bomb. 

 

Debris between Jupiter and Mars failed to form a planet because Jupiter’s gravity was so strong that assembling planetesimals were torn apart. That belt of debris comprises asteroids ranging up to 1,000 kilometers across. Unlike comets, asteroids are typically made of metals such as iron and nickel, silicates similar to stone found on earth, and carbon. As these asteroids are influenced by the competing gravities of Jupiter and the sun, they collide and form dust and small debris. Given the gravitational interaction of the sun and Earth, it’s thought that this dust and debris form an irregular ring close enough to Earth for material to be captured by Earth’s gravity.16 The captured dust and small debris (shooting stars) are slowed by our atmosphere and fall harmlessly to Earth.17 It’s estimated that from tens of thousands to hundreds of thousands of tons of this matter fall to Earth each year. 

 

As Jupiter’s gravity dislodges asteroids from the asteroid belt, some are drawn toward the sun and inner planets. Within about 10 million years, the orbits of the larger of such asteroids will inevitably intersect the orbits of Mars, Mercury, Venus, Earth, or the sun. Meteor Crater in northern Arizona is 1.2 kilometers in diameter and was formed about 50,000 years ago by a metallic meteor about 30 meters across. Meteors larger than a kilometer across, on average, arrive once every 300,000 years. Such meteors would have energies in excess of 600 thousand Hiroshima bombs. On average, meteors about 10 kilometers across strike the Earth every 100 million years. It’s this type of meteor that ended the Cretaceous period and the dinosaurs as well as about 70 percent of Earth’s species.18 

 

In the 20th century we observed two major impacts. In 1908 a meteor believed to be made up of silicates impacted the Tunguska Valley in Siberia with an energy estimated to be equal to 800 Hiroshima bombs. It was about 60 meters across and did not leave a crater because the silicates were loosely connected fragments that burst apart on impact with the atmosphere. Beneath the impact point it left an area 50 kilometers across of flattened and burnt trees.19 The second major impact was the Shoemaker-Levy 9 comet collisions with Jupiter that began July 16, 1994. The comet fragments had an estimated combined energy equivalent 250 million Hiroshima bombs. A less significant recent event occurred when a meteor entered Earth's atmosphere over Russia on 15 February 2013 and exploded in an air burst over Chelyabinsk. The explosion had a total kinetic energy equivalent to approximately 30 Hiroshima bombs.

 

Although craters on the moon are numerous, on Earth the effects of wind and water erosion, sedimentation, volcanism, and plate tectonics eventually destroy evidence of impact craters. To date, the remnants of about 160 impact craters have been found on Earth. For the next crater to be formed is just a matter of time. In 1996, an asteroid measuring between 300 and 500 meters across came within 450,000 kilometers of Earth, the distance that such a comet would travel in less than 6 seconds.20 It’s estimated that there are about 2,000 Earth orbit—crossing asteroids larger than one—half mile across.21

  

Given the chaotic process by which clouds of matter are converted into solar systems, the arrangement of our sun and planets is clearly one of many possible essentially stable states a collapsing cloud of gas, dust, ice, and debris can achieve. Recent research indicates that other solar systems have evolved different arrangements of suns, planets, moons, comets, and asteroids. Given the nature of solar system formation, stellar debris and interstellar material formed long before our sun ignited are the stuff of which the Earth is made. And inasmuch as our bodies derive from Earth, the dust from which we come and to which we return is the dust of ancient stars.

 

Our Planet

Why does the Earth have a moon and why is one day 24 hours long? The Earth began to form about 4.6 billion years ago as an orbiting mass of material larger than things around it. Over time, its increasing gravity attracted matter from farther and farther away. Eventually it grew to become a small planet. For over a hundred million years it grew in size as it accreted everything within reach of its gravity or that crossed its path at a relative speed slow enough to permit capture. As Earth collided with planetesimals, perhaps the size of the moon, it was knocked apart only to be brought together and crushed into a sphere by its collective gravity. Under the influence of its gravity, iron, heavy radioactive elements, and other very dense materials sank and formed Earth’s core while basalt, granite, and other lighter materials rose to form an outer shell. As radioactive material decayed to more stable forms, its radiation heated Earth’s core. Countless meteor and planetesimal impacts on Earth’s surface created a layer of molten magma hundreds of kilometers thick. For millions of years volcanoes poured lava onto the surface and into newly formed impact craters.

 

Computer simulations indicate that a mass larger than Mars might have collided at a shallow angle with the Earth’s mantle about 4.5 billion years ago. The collision would have ejected material both into space and into Earth orbit. By the time gravity resettled the debris Earth had acquired a moon. The impact was apparently slightly off center resulting in the moon’s orbital plane being about 5 degrees different from the Earth’s. Were the orbital planes exactly the same we would have solar and lunar eclipses each month at the new moon and the full moon. When the moon first formed, its distance from Earth was about half what it is today, resulting in much greater lunar tides than we experience today. Although our present lunar month is about 29.5 days, the first lunar month was considerably shorter. Fossil records of tidal activity contained in “tidal rhythmites” formed about 1 billion years ago indicate that the Earth rotated about 30 percent more rapidly, completing a day in just over 18 hours and a year in 481 days. As the moon interacts with Earth’s rotating gravitational field, Earth’s rotational speed is slowing while the moon’s orbital velocity and diameter are increase. In other words, the distance from Earth to the moon is increasing and Earth days are getting longer.22

 

Why does Earth have mountains, oceans, a magnetic field and an atmosphere? About 4.4 billion years ago Earth began to retain its atmosphere. Churning molten material in Earth’s core produces a magnetic field around the Earth strong enough to move compass needles, shape charged particles from the sun into the Arora borealis, and to prevent gases in Earth’s atmosphere from being blown away. By about 4.2 billion years ago Earth reached its present diameter of about 8,000 miles. The core is about 4,000 miles in diameter and is made up of iron and nickel. Heat from the core creates convection currents in the less dense mantle between the core and Earth’s crust. Typically no more than about 20 miles thick, all but the lightest crust material is churned under by the slowly roiling mantle. Continents are made of low density material that floats on and is driven by the slowly moving mantle convection below. We perceive this motion as continental drift. The continental crustal material is too light to be drawn into the churning mantle and can preserve some of the Earth’s oldest rocks. When mantle currents stretch and shear continents, they form rift valleys and fault zones. When continents collide without one continental plate slipping beneath the other, mountain chains form, as the light crustal material has nowhere to go but up. When one plate slips beneath another as they are driven together, crustal rock melts from heat generated as the plates scrape past each other. Upwellings of molten rock at these plate boundaries break the surface as volcanoes. What we call the Pacific ring of fire are volcanoes around the Pacific plate. These forces together with erosion from wind and water have destroyed most of Earth’s earliest rocks. However, some Australian zircons date back about 4.3 billion years. There are a few theories regarding the source of water in Earth’s oceans. One is that it was delivered to Earth by water-containing comets. Another is that hydrogen and oxygen contained in Earth’s mantle rock combined when the rock was melted by volcanic, tectonic, and other means.

 

It’s thought that the early atmosphere formed when the iron/nickle core coalesced and volcanic activity vented gasses from the interior to Earth’s surface. It is estimated that this process could have produced over 80 percent of our atmosphere within about one million years. The earliest known atmospheric composition was nitrogen, hydrogen, carbon dioxide, water vapor, sulfur dioxide, hydrochloric acid, methane, and ammonia. Atmospheric oxygen, primarily a byproduct of photosynthesis, would not begin to appear in significant quantities until about 2.5 billion years ago and would take about 600 million years to reach present levels. In time, comet and asteroid impacts diminished on an Earth thick with clouds in an orange sky. Although the sun’s energy output was perhaps 25 percent less than it is today, some believe that greenhouse gases in the early atmosphere (methane, ammonia, and carbon dioxide) trapped solar radiation to a greater degree than does our atmosphere today. As the sun’s energy output increased over the ensuing billion years, Earth’s surface temperature did not rise proportionately because heat-trapping greenhouse gasses gradually diminished.23

 

As Earth continued to cool, complex molecules delivered to Earth by comets and asteroids were no longer destroyed by intense heat. Some theorize that single-celled microorganisms might have incubated on other planets and could have arrived on Earth if impacts on other life-supporting planets ejected organism-containing fragments (tektites) that ultimately reached Earth. Such organisms would have been released into the oceans and atmosphere. In any event, compounds formed in space by natural stellar processes would have been available to begin combining on a sterile Earth. Such compounds would have interacted in storms, churning oceans, and waters heated by geothermal activity. Without oxygen, the atmosphere had not formed the ozone layer that today filters out the sun’s ultraviolet radiation. This is pivotal to the evolution of life because ultraviolet radiation damages DNA. However, while ultraviolet radiation could reach Earth’s surface, it could not penetrate water. After some nine billion years of evolving since the Big Bang, the universe had produced one of perhaps countless planets with primordial chemistry that was ready to support self-organizing and self-replicating molecules. 

 

Copyright 2019 Research Associates, LLC

 

Creation According to Science Endnotes

1.   Peebles, P. James E., Schramm, David N., Turner, Edwin J., and Kron, Richard G., “The Evolution of the Universe,” in Scientific
      American, October, 1994, p. 53.

2.   Cowen, Ron, “Opening the Door to the Early Cosmos,” in Science News, August 3, 1996, Vol. 150, No. 5, p. 68.

3.  “Satellites hint sun is growing stronger,” in Science News, September 27, 1997, Vol. 152, p. 197.

4.   Cowen, Ron, “The Once and Future Sun,” in Science News, March 26, 1994, Vol. 145, pp. 204-5.

5.   Kirshner, Robert P., “The Earth’s Elements,” in Scientific American, October, 1994, p. 44.

6.   Weinberg, Steven, “Life in the Universe,” in Scientific American, October, 1994, p. 59.

7.   Cowen, Ron, “Chemical Pathway Links Stars, Meteorites,” in Science News, November 6, 1993, Vol. 144, p. 292.

8.   Kirshner, Robert P., “The Earth’s Elements,” 1994, pp. 59-65.

9.   Cowen, Ron, “Bright Comet Poses Puzzles (Hyakutake’s Tails of Mystery),” in Science News, June 1, 1996, Vol. 149, pp. 346-7.

10.  Kirshner, Robert P., “The Earth’s Elements,” 1994, pp. 59-65.

11.  “A moon for Dionysus,” in Science News, September 27, 1997, Vol. 152, No. 13, p. 200.

12.  Cowen, Ron, “The real meaning of 50 billion galaxies,” in Science News, February 3, 1996, Vol. 149, No. 5, p. 77.

13.  Winters, Jeffrey, “The Answer in the Voids,” in Discover Magazine, March, 1996, p. 27.

14.  Frank, Adam, “In the Nursery of the Stars,” in Discover Magazine, February, 1996, p. 30.

15.  Gehrels, Tom, “Collisions with Comets and Asteroids,” in Scientific American, March, 1996, pp. 54-59.

16.  Gehrels, Tom, “Collisions with Comets and Asteroids,” 1996, pp. 54-59.

17.  Cowen, Ron, “New link between Earth and asteroids,” in Science News, November 6, 1993, Vol. 144, p. 300.

18.  Gehrels, Tom, “Collisions with Comets and Asteroids,” 1996, pp. 54-59.

19.  Gehrels, Tom, “Collisions with Comets and Asteroids,” 1996, pp. 54-59.

20.  “Old equipment finds big asteroid nearby,” in Science News, June 8, 1996, Vol. 149, No. 23, p. 365.

21.  “The Doomsday Asteroid,” WGBH Educational Foundation, Nova program #2212, Air Date 10/31/95, Journal Graphics, Inc.,
       Transcript, p.5.

22.  Monastersky, Richard, “The Moon’s Tug Stretches Out the Day,” in Science News, July 6, 1996, Vol. 150, No. 1, p. 4.

23.  Allegre, Claude J., and Schneider, Stephen H., “The Evolution of the Earth,” in Scientific American, October, 1994, pp. 66-75.

EPILOGUE AND ESSAYS
REFERRED TO IN THE BOOK

 

Epilogue

I was asked by two friends who critiqued the nearly completed manuscript to explain what I understand reality to be in light of the strange reality of quantum mechanics. The following explanation, therefore, is written for readers familiar with the basic concepts of quantum mechanics.

 

To begin on the same page, I thought the following summary would be helpful. Long-held opinions about material reality were challenged in 1801 when light (photons) was used in double-slit experiments. In those experiments, photons passed through double slits and then onto a screen. If light consisted of particles, as Isaac Newton thought, photons would pass through the slits and form predictable particle-like patterns on the screen. What actually appeared on the screen was a double-slit interference pattern of bright and dark bands characteristic of waves, not particles. The bright bands were constructive interference regions where photons would most likely appear on the screen. Since this early experiment, electrons, neutrons, and collections of hundreds of atoms have been passed through double slits and produced interference patterns similar to that of photons. In addition, it was found that an interference pattern appeared even when a single photon passed through a single slit. More recently, experiments indicate that antimatter also behaves as waves.1 The challenge these experiments pose for our view of reality is, if particles can behave as waves, is our view of a material reality wrong? 

 

Quantum mechanics can represent the location of a photon as a mathematical expression called a wave function. Such wave functions can indicate the probable positions of photons in double-slit interference patterns. However, quantum mechanics cannot yet explain why the wave and particle states of photons behave as they do. 

 

While a number of concepts have been proposed, including the Many-Worlds Interpretation, I describe two here. The first posits that the location of photons on double-slit screens is probabilistic, that the photons follow no particular path to the diffraction pattern screen, and that the photons transition from non-real waves to real particles by means of wave function collapse, which is thought to be initiated by measurement, gravity, observation, or some form of consciousness. The second posits that a photon’s position is determined by interacting with its associated pilot wave and that photons travel in one path from a slit to the interference pattern screen. In this theory, the pilot wave passes through both slits, which introduces an interference pattern as it interacts with its associated photon that traveled through one slit. The photon’s path is determined by its prior position and velocity. Since the photon’s ultimate path and position are deterministic, the pilot wave model does not involve real particles with non-real waves or the need for wave function collapse to materialize the photon. However, knowing the exact position and velocity of a quantum particle is problematic for the pilot wave conjecture. Both of these proposed models have unresolved issues.

 

Where does that leave our understanding of reality? Until now, what we know about the nature of things has been learned by thinking analytically. Our progress as humans, to a great extent, is the result of scientific discoveries about Nature. Those discoveries, instead of arriving fully formed, have been refined over time as more is learned about Nature. In one example, Newton’s laws of mechanics were modified by Einstein’s theory of relativity. Will the mysterious nature of quantum mechanics follow that same pattern? 

 

Perhaps the reality our ancestors experienced as their DNA was being refined involved no significant relativistic or quantum mechanical effects. While we now know that time passes more slowly for an eagle diving to seize a sloth, that fact appears to have little or no influence on the genetic evolution of eagles and sloths. 

 

Will quantum mechanics change our view of reality? Inasmuch as the scientific method has been effective at explaining reality by assuming that reality exists regardless of how we perceive it, subject to verifiable contradictory evidence, I see no reason to change that assumption.

 

One final note—while Darwinian evolution came into being with Newtonian physics, today, research is underway to determine the possible effects of phenomena such as quantum superposition, quantum coherence, and electron tunneling on biological processes such as photosynthesis, cellular respiration, vision, enzymatic activity, and DNA mutation.

 

Essay 1

Brain Evolution
 

DNA Self-organizes

How did the human brain evolve from Earth’s first self-organizing molecules to the brain we inherited? Some Egyptians thousands of years ago believed that life could generate spontaneously from non-living matter virtually overnight. This view probably resulted from observing insects that grew from microscopic eggs, such as the scarab. The Greco-Roman view of how life began spontaneously (autogenesis) was recounted by the Roman philosopher and poet Titus Lucretius Carus (99-55 BCE): 

 

Life does not differ essentially from other matter; it is a product of moving atoms which are individually dead.
As the universe took form by the inherent laws of matter, so the earth produced by a purely natural selection all the species and organs of life.

 

Nothing arises in the body in order that we may use it, but what arises brings forth its own use...1 It was no design of the atoms that led them to arrange themselves in order with keen intelligence…but because many atoms in infinite time have moved and met in all manner of ways, trying all combinations... Hence arose the beginnings of great things—and the generations of living creatures...2 Many were the monsters that the earth tried to make: …some without feet, and others without hands or mouth or face, or with limbs bound to their frames... It was in vain; nature denied them growth, nor could they find food or join in the way of love... Many kinds of animals must have perished then, unable to forge the chain of procreation—for those to which nature gave no [protective] qualities lay at the mercy of others, and were soon destroyed.3

 

A few ancient Greek philosophers pondered marine fossils and concluded that we evolved from fish.4 Today, we know that RNA and DNA are the molecules of life that store the information that defines every life form. DNA (deoxyribonucleic acid), the now famous double helix or twisted ladder, consists of two long, twisted chains of nucleotides made up of the amino acids adenine, thymine, cytosine, and guanine (ATCG). It is capable of replicating itself and of synthesizing RNA. RNA (ribonucleic acid), a molecule found in all living cells, consists of a long usually single-stranded sequence made up of phosphate and ribose and the amino acids adenine, uracil, cytosine, and guanine (AUCG). In general, DNA produces messenger RNA that manufactures proteins such as enzymes, hormones, antibodies, muscle, and other tissues—the essential components of living organisms. The kind of protein produced is determined by the nucleotide sequences (genes) engaged in the protein’s production.

 

The importance of DNA cannot be overstated. While shamans look to myths to explain the creation of life, scientists investigate DNA. Even though DNA is capable of making RNA, some scientists theorize that the first DNA derived from RNA, and that RNA might have derived from an even earlier and simpler molecule that RNA ultimately replaced.5 Whatever the process was, scientists engaged in researching the prebiotic chemistry of Earth are theorizing that the first self-replicating system was either simple or could be generated simply. One reason for this is that self-organizing molecules appeared soon after the Earth formed and cooled. Although the sequence of events that gave rise to DNA is not known, that sequence does not appear to be unknowable. Given the amount of knowledge accumulated in recent decades by molecular biologists, chemists, and biochemists, it’s probably just a matter of time before self-replicating molecules that reproduce the origin of life are manufactured in someone’s laboratory. 

 

It’s not likely, however, that the process that gave rise to the first self-replicating molecule is taking place somewhere in Earth’s biosphere today. Reactions that create complex organic molecules do not fare well in the presence of oxygen. Earth’s atmosphere contained little if any oxygen 4.5 billion years ago, when the process that led to self-replication probably began. In addition, lightning, meteorites, comets, and interstellar dust could have provided more than enough amino acids for Nature to assemble them into the first self-replicating organic molecules in Earth’s prebiotic environment.6

 

Once the first self-replicating molecule formed out of the primordial soup, well before 3.7 billion years ago,7 the mechanism for retaining trial and error knowledge was in place. Between 4.5 billion and 3.7 billion years ago DNA strands had evolved to perhaps 256 genes, sufficient to produce the equivalent of modern bacteria or archaea.8 Primordial microbes would have lived in an atmosphere without oxygen and some would have derived their energy from sulfur compounds, perhaps near volcanoes or hydrothermal vents at sea bottom tectonic boundaries. 

 

Early DNA strands were circular loops attached to cell walls. These early cells had no nucleus and their membranes or cell walls were rigid, providing both protection and structural support. They took nourishment from their surroundings by secreting enzymes to dissolve nearby debris and absorbing the nutrients, a method used by some insects today. By about 3 billion years ago, DNA in some organisms had evolved to define a cell that had lost rigidity in its outer cell wall. This type of cell was a flexible blob that supported itself with rigid internal structures. This amoeba-like cell was able to increase in size to 10,000 times the volume of a small bacterium. Its outer membrane could fold and it had evolved a nucleus, perhaps formed by the outer membrane folding a pouch with DNA inside. The pouch then detaching from the outer membrane to move freely within the cell. This cell could consume entire bacteria by enfolding them, sealing off the pouch at the other membrane, and discharging enzymes into the pouch to digest the prey. In other words, this cell could eat. 

 

Some prey with protective characteristics settled into a symbiotic relationship with its host cell. They became cell organelles. The unique DNA of such acquired bacteria eventually migrated to the nucleus and became part of the ever-growing DNA strands that made-up the cell’s genetic code. By now, the cell contained several thousand organelles the size of small bacteria. One such plant-like organelle contained plastids (chlorophyll) capable of using the energy of sunlight to produce a source of energy for cell function. Another organelle, peroxisomes, which contained enzymes that catalyze the production and breakdown of hydrogen peroxide, helped in the conversion of food into energy and metabolized fatty acids. It’s thought that this organelle in particular assisted its complex cell in dealing with the toxins created by the rising level of oxygen in the environment between 2 billion and 1.5 billion years ago. However, the organelle that energized cells to take advantage of newly available oxygen was the chondriosome (mitochondria). It contained enzymes important for cell metabolism, and particularly those enzymes responsible for the conversion of food to usable energy in the form of ATP (adenosinetriphosphate). ATP is the molecule that energizes muscle contraction and sugar metabolism. It was a pivotal event in cell evolution. Between 3.7 billion and 1.5 billion years ago, DNA had grown to produce complex single cells. The modern equivalent of such a cell has DNA with about 12.5 million nucleotide base pairs.9

 

These large single-celled creatures stored all their eating, survival, and reproduction knowledge in their DNA as ATCG nucleotide sequences. However, for multicellular animals to evolve, functions normally carried out completely by a single cell must be carried out by different groups of cooperating cells. For example, reproduction by cell division carried out by a unicellular organism must be performed by a specialized group of cells in a multicellular organism. Unlike the more or less fully utilized DNA of the unicellular organism, only portions of the DNA of multicellular organisms are used by specialized cells to accomplish their limited functions. Developing these specialized cells is called “differentiation.” Clearly, single cell DNA had to develop a means of intercellular communication to enable multicellular differentiation to occur.

 

If functions are to be divided successfully among groups of specialized cells, they must be able to coordinate their activities. To accomplish this, the DNA of one cell type must be able to regulate the activity of DNA in other cells. Such regulation can be accomplished if the DNA of one cell manufactures messenger molecules or proteins capable of regulating the activity of DNA in other cells. For example, in our bodies the flight or fight response to fear involves the release of adrenaline and noradrenaline. The adrenal glands secrete these molecules into the blood stream to increase the heart pumping rate, blood pressure, metabolic rate, blood sugar concentration, and blood flow to the muscles and to the primitive “reptilian” part of the brain. Blood flow to the thinking cerebral cortex decreases and other essential bodily functions are slowed.10 In much the same way, messenger molecules can regulate gene expression during gestation.

DNA Enables Cells to Cooperate
What took place in early unicellular evolution to set the stage for multicellularity? A clue might be found in the behavior of the Dictyostelium amoeba (commonly referred to as “Dicty”), which has a cellular structure similar in many ways to our own. Multicellular organisms such as plants, fungi, and animals evolved from what is called the “eukarote” line of organisms. We are multicellular eukarotes and Dicty are unicellular eukarotes. At some point in our ancestry, a unicellular eukarote mutated to form multicellular eukarotes. It’s possible that our first multicellular eukarote ancestor had functional characteristics very similar to the present day Dicty. What is interesting about Dicty is that they communicate with and influence each other on a grand scale to ensure their survival. 

 

Dicty normally eat bacteria and reproduce asexually by dividing. When bacteria become scarce and a colony of Dicty is in danger of starving, the first to detect the scarcity begins to release waves of messenger molecules. When the messenger molecules reach other Dicty they begin to move toward the source and also begin emitting their own waves of messenger molecules. As this process ripples through the colony Dicty accumulate into a mound. Once in a mound, the concentration of messenger molecules is high enough to trigger other changes. The Dicty attach to each other by means of cellulose and other proteins and travel as a mass by jostling past one another. The mass begins to take on a slug-like form and it appears that the most recently divided Dicty rise to the top of a stem-like mass and move it through the soil by heading toward heat and light. Next the cells at the stem tip rise up as different genes activate at different distances from the tip. After rising, cells at the tip travel down through the mass to form a stalk that supports the remainder of the colony that, by now, is acquiring a somewhat spherical shape. Some Dicty form a cup at the top of the stalk that supports the sphere while others form a disk at the bottom, anchoring it to the soil. By this time, the entire mass has taken on a spore-like appearance. In time the top sphere of Dicty might be carried away on the feet of animals or by some other means to be relocated to a possibly bacteria rich environment where they can flourish. Keep in mind that the entire process began with the prospect of starvation, and it’s likely that each genetic mechanism employed by the Dicty accumulated over time in a trial and error process of adapting to changing environmental conditions.11

 

What might we learn from these unicellular organisms about the evolution of multicellular animals? We know that Dicty can communicate, change their cellular properties (differentiate), and function in a coordinated way—all this without a common skin or a common first cell (egg). These independent cells contain DNA that evolved the capacity to manufacture messenger molecules capable of triggering all these effects. Is it possible that the first multicellular organism mutated from a unicellular organism that had already evolved DNA capable of triggering complex coordinations, behaviors, and physical differentiations? 

 

Even if DNA can manufacture messenger molecules, how would a unicellular organism create extra cells that are not simply copies of itself? And even if a cell can make extra cells, how would the extra cells become different? DNA mutations had to occur that enabled a single cell to divide a number of times. Unlike cancers, which are clusters of continuously dividing cells, a multicellular organism stops dividing at some point. In addition, the extra cells produced had to respond to each other’s messenger molecules as well as differentiate their functions in a way useful to the survival of the organism. 

 

How did the extra cells differentiate into useful organs? By this stage in biological evolution, DNA sequences were getting to be quite long. Long sequences or strands of DNA are called “chromosomes.” Nucleotide sub-sequences within chromosome strands that create specific proteins are called “genes.” The complex arrangement of DNA with its messenger molecules was a prerequisite to the development of cell differentiation. Messenger molecules have shapes that fit into specific sections of a DNA helix. Once in place, the molecules regulate the DNA’s protein production by activating or deactivating nearby genes. The process becomes richly complex as molecules regulate genes that produce proteins that, in turn, regulate genes on the same DNA or on DNA in other cells that in turn produce other messenger proteins, and so on. For cell differentiation to occur, developmental genes must be activated to produce messenger molecules, and other genes must be deactivated in the proper ongoing sequence until differentiation is completed. In some cases, the presence of protein from one developmental gene can inhibit the function of protein from another developmental gene.12

 

A hierarchy of developmental genes acting sequentially accomplishes differentiation. Developmental genes that determine an embryo’s overall characteristics, such as the head, thorax, and abdomen are supplemented by developmental genes that determine specific characteristics within those primary domains. As developmental genes manufacture regulating proteins the concentration of those proteins decreases with distance from the originating genes. This is called “a concentration gradient.” A minimum concentration of regulating proteins is required for regulation to take place. For example, imagine that developmental genes in an oval embryo were to activate at each end of the oval’s long axis as well as on opposite sides of the center of the oval. Messenger molecule gradients from those genes would spread throughout the embryo with protein concentrations greatest at their points of origin and progressively weaker away from those points. The different proteins would combine at various concentrations throughout the embryo. As the developmental proteins in high enough concentrations promote and inhibit gene activity in cells of the embryo, DNA in those cells creates its own local protein gradients. The overlapping gradients would provide a very complex matrix of DNA activation and inhibition capable of producing very complexly differentiated cells.13 

 

One way of visualizing messenger molecule concentration gradients is to imagine two stones being dropped simultaneously into a still pond. As their ripples meet and overlap, a complex pattern of interacting ripples would develop. Now imagine the stones to be of different sizes. Although the pattern of interacting ripples would change, it would still be symmetrical in one axis, as symmetrical as the body patterns of complex differentiated organisms. A more robust and internally asymmetrical analogy would be created if you could imagine three-dimensional or spherical waves from two stones that spawn secondary spherical waves from a few asymmetrically placed pebbles, which in turn spawn tertiary spherical waves, et cetera. 

 

The mathematical function that closely mimics this kind of sequential execution of multiple DNA instructions is the fractal or Mandelbrot set. Fractals are simple mathematical expressions that, by repeating each calculation beginning with the result of the previous calculation, can produce extremely complex irregular shapes and surfaces similar to those found in Nature.

 

 

A Small DNA Mutation Makes a Big Difference

Research indicates that very early in the evolution of multicellular organisms, the most fundamental developmental genes inverted their differentiation functions. The result of this DNA mutation was that the gut and central nervous systems in vertebrates were reversed relative to organisms with segmented bodies (lobsters, crabs, and shrimp).14 We humans are vertebrates with our spines at our backs and our intestines in front. A shrimp has its gut in back (opposite its legs) and its nervous system in front. It should be apparent that relatively small variations in developmental genes can produce large differences in body patterns. However, the complexity of large animals requires long DNA sequences (many genes) to provide the necessary code. This, combined with unlimited potential for cell division, can produce all sorts of creatures. 

 

How many genes does it take to produce different types of body patterns? Peter Holland, a molecular zoologist at the University of Reading in England made the following observation:

 

You might expect that as you look at a range of different animals, you would see widely varying numbers of genes. If you looked through the vertebrates, you would expect mammals to have more genes than reptiles and reptiles to have more genes than fish. But that turns out to be wrong.

 

What our preliminary data suggest is that all the vertebrates have roughly the same number of genes, and all the invertebrates have roughly the same number of genes. But there was a jump [in the number of genes] between invertebrates and vertebrates.15

 

Holland suggested that a mutation in invertebrate reproduction could have doubled the number of chromosomes in its offspring and made the evolution of vertebrates possible. Inheriting an extra copy of one chromosome is common. It’s the cause of Down’s syndrome and other birth defects. Doubling all of an organism’s chromosomes would be extraordinarily rare. Rare or not, given hundreds of millions of years and innumerable reproduction opportunities, it might have happened twice. The first time is thought to have been prior to the appearance of vertebrates, about 520 million years ago, and the second just prior to the appearance of jaws in vertebrates, about 460 million years ago. It’s thought that the extra DNA, and in particular the doubling of developmental genes, made it possible for more complex body plans to evolve. It’s thought that a similar doubling was responsible for the evolution of flowering plants.

 

At about 520 million years ago, even though our DNA was producing differentiation proteins needed for our present fundamental body plan, our ancestors had no skeletal structure. It is theorized that a constant need for calcium in an environment with a changing availability of calcium led our fresh-water marine ancestors to evolve a calcium storage capacity. In time, these calcium storage structures were put to good use by evolution and became our spinal columns and related skeletal parts. In addition, chromosome doubling provided sufficient genes to support the formation of a very complex head with paired sensory organs and a three-part brain. An alternative theory suggests that the first calcium concentrations evolved to protect sensitive neural structures and progressed to provide the protective armor seen in the fossils of bony fish.

 

As these few inch-long, fish-like invertebrates were evolving into vertebrates, bony arches that supported their gills evolved from their forward-most ribs. They had no jaws and ate by swallowing without biting or chewing, much like lamprey eels. It’s theorized that, just prior to 460 million years ago, things changed with the second chromosomal doubling. The additional genes would have supported a number of complex innovations including adapting the bony gill arches to close the mouth and allow water to oxygenate the gills more quickly. This trait would have improved breathing performance, energy production, and speed, and as an added benefit it would have enabled these new vertebrates to suck in and clamp down on prey. Clamping became adapted with stronger muscles and various means to hold prey securely.16 It was a development that would define much of the world as we know it today. 

 

In time, plant and flesh-eaters would evolve extraordinary capacities to maximize the benefit of their highly efficient jaws. These marine vertebrates gave rise to amphibians, birds, reptiles, and mammals. No evidence of chromosome doubling after 460 million years ago has been found. In the intervening 460 million years, mutations and natural selection pressures caused branching of DNA evolution that resulted in an enormous variety of life forms, most of which are now extinct. 

 

Representative of the complexity of early bacteria, the DNA of E. coli bacteria of today contains about five million nucleotide base pairs while yeast DNA contains about 12.5 million base pairs. Fruit fly DNA contains about 160 million base pairs, and the DNA of humans contains about three billion base pairs.17 Those three billion nucleotide base pairs make up about nineteen thousand genes, about half of which might be involved in some way with our central nervous system.

 

 

Evolution before Darwin

In the 19th century, Darwin was able to piece together the missing elements of biological evolution. Before Darwin, the early Greeks envisioned elements of the theory of evolution. Anaximander (610-546 BCE) thought that organisms arose by gradual stages and that land animals were once fish.1 Empedocles (500-430? BCE) believed that Nature produces every kind of organism with some capable of propagating themselves and meeting the conditions of survival. Anaxagoras (500?-428 BCE) said that all organisms were originally generated out of earth, moisture, and heat, and thereafter from one another,2 and that the upright posture of humans freed their hands for grasping and enabled them to develop beyond other animals.3

 

Unfortunately, Aristotle preferred his concept of “entelechy” to the natural selection of Anaximander, Empedocles, and Anaxagoras. He [Aristotle] rejected Empedocles’ notion of the natural selection of accidental mutations:

 

There is no fortuity in evolution; the lines of development are determined by the inherent urge of each form, species, and genus to develop itself to the fullest realization of its nature. There is design, but it is less a guidance from without than an inner drive or “entelechy” by which each thing is drawn to its natural fulfillment.4

 

In 1756, Karl von Linne (1707-1778) placed humans in the primate-order classification of animals in his work Systema Naturae. George de Buffon (1707-1788) suggested an ancestor common to all living beings in his work Natural History. Erasmus Darwin (1731-1802), the grandfather of Charles Darwin, proposed that “animals vary and transform through behavior which is provoked by need.” Jean-Baptiste de Lamarck (1744-1829) proposed that an animal that travels on all four limbs might evolve to travel on two. The preface to On the Origin of Species by Way of Natural Selection presents a more complete review of theories leading up to Charles Darwin’s work. In the text itself, Charles Darwin offers his view of the nature of evolution, to wit:

 

How do those groups of species, which constitute what are called distinct genera, and which differ from each other more than do the species of the same genus, arise? All these results, … follow inevitably from the struggle for life. Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive.

 

In addition to observing accurately the result of DNA’s constant refinement of genetic knowledge, to which he refers as “from whatever cause proceeding,” Darwin realized that the competition for life begins with abundant offspring competing with each other for limited resources. A most extreme version of this was recently observed in a species of shark in which fully functioning siblings cannibalize each other during gestation. One might describe it as a kind of prenatal survival of the fittest.  Another of Darwin’s contributions to our understanding of biological evolution is his realization that offspring with genetic variations, which coexist with related offspring absent the variations, constitute branching in evolution’s tree of life.

 

Early Life

In an attempt to reconstruct how the accumulation of slight variations over more than 3.5 billion years has produced the human brain, visualize in your mind’s eye, if you will, the unseen changes in DNA that underlie overt changes in the fossil record we are about to consider. 

 

There are three main branches on the tree of life. The bacteria branch, which includes cyanobacteria; the eukarya branch, which includes plants, animals, and fungi; and the archaea branch, which are bacteria-like organisms identified as distinct from bacteria in 1977. Archaea are the least understood of the three branches.5, 6 Research shows that archaea differ from bacteria in the makeup of their DNA and in the fact that they derive their energy using, e.g., hydrogen and carbon dioxide. Bacteria employ, e.g., sulfates (anaerobic) and oxygen (aerobic) in their energy-generating processes. Whether archaea self-assembled prior to bacteria is unclear. What is clear is that self-assembly happened before 3.8 billion years ago. At that time, about 200 million years after the last meteorite bombardments, primitive organisms left their remains in what is now Greenland.7 Within another 300 million years, however, bacteria that derived their energy from sulfate reactions encountered what to them was an ecological disaster. Bacteria much like today’s cyanobacteria adapted to use sunlight to convert water and carbon dioxide into glucose while producing oxygen as a byproduct. This began a process that displaced sulfate reactions as a dominant driving force of life. Inasmuch as oxygen readily combines with many mineral compounds, newly evolving cyanobacteria began to create what would become our biosphere. Although oxygen to varying degrees was toxic to anaerobes, they were not destroyed. Instead, they were relegated to live in places where oxygen levels were low enough for them to exist away from oxygenated water and the atmosphere.

 

Primitive cyanobacteria thrived in the surface waters of the Earth’s oceans, which, at that time, were filled with dissolved iron compounds. As oxygen was produced it combined with iron compounds forming precipitates of iron oxides, and eventually transformed the oceans. Red deposits of iron-rich sediments layered the ocean bottoms leaving behind the clear water we see today. In time, with virtually no iron compounds remaining with which to combine, oxygen bubbled up from the oceans to transform the atmosphere. 

 

Early life forms survived a glacial episode that reached almost to the equator 2.2 billion years ago,8 and by about 1.3 billion years ago simple bacteria had experienced an enormous number of mutations. These mutated descendants had acquired nuclei, were thousands of times larger than simple bacteria, and assimilated various bacteria symbiotically as organelles. 

 

It’s possible that these single-celled organisms developed the cooperative capabilities of present-day Dictyostelium amoebae, or “Dicty.” Another 200 million years of mutations produced rudimentary multicellular organisms without nervous or circulatory systems. This line of cells gave rise to anemones and corals. Multicellular life survived another glacial episode about 700 million years ago. Some believe very low levels of atmospheric carbon dioxide during that time indicate that the planet surface froze completely for about 10 million years.9, 10 

 

At about this time a developmental gene inversion is believed to have occurred. Such an inversion would have made possible body patterns with the central nervous system and intestinal tract reversed relative to the direction of the limbs, such as is seen in shrimp today. Thereafter, about 50 major body patterns evolved, including segmented bodies, invertebrates, and vertebrates. Among these were the first jellyfish. Although the Burgess shale deposits in the Canadian Rocky Mountains contain many fossils from this period, the dearth of hard parts in these squishy life forms makes the fossil record incomplete and difficult to interpret. What is very clear is that life was proliferating dramatically, perhaps with the aid of two gene doublings at about 520 and 460 million years ago.11, 12 

 

It’s theorized that gill arches evolved into jaws. Heads and sensory organs became more complex. Three-part brains began to appear along with calcium-storing spines and skeletal parts. Filter feeders such as starfish and sea urchins evolved. Ammonite descendants of jellyfish developed well-defined tentacles, shells, and eyes. In turn, descendants of ammonites, such as the nautilus, retained the shell, while other descendants such as the cuttlefish, octopus, and squid successfully adapted without shells. Plantlife was coevolving and generally preceded animal life in exploiting new environments. 

 

Plants and animals had become symbiotically dependent on an oxygen-carbon dioxide cycle. By 550 million years ago, while oceans were supporting evolving plants and animals, the land was lifeless. Plate tectonics, wind, and rain had created and reshaped continents and mountain ranges. The roughly 10,000 species that had evolved by this time were adapted to living in salty ocean water, not in freshwater runoff from the continents. Although rivers, lakes, wetlands, bays, and dry land were devoid of animals, plants were beginning to adapt to freshwater. 

 

There were two fundamental changes needed for ocean creatures to adapt to living in fresh or brackish water. The first was to evolve a capacity to excrete water that accumulated in their cells in the absence of sufficient salt. The second was to evolve a capacity to store calcium that was not consistently available in fresh-water environments. Without calcium, muscles cannot function. 

 

By about 530 million years ago, soft-bodied vertebrates had evolved. The cartilaginous vertebrae of their rudimentary spinal columns were calcium repositories. Within 30 million years, vertebrates living in brackish water evolved fresh-water-adapted kidneys, calcium-regulating bone, and blood-salt-level-regulating circulatory systems. By 500 million years ago, proto-fish vertebrates with scales or thin bony plates and the beginnings of a limbic brain had evolved. With no pectoral or pelvic fins they swam erratically, and, with no jaw, it’s likely that they were like modern lamprey ells, or became filter feeders or scooped up nutrient-rich mud to sustain themselves.

 

About 440 million years ago, when trilobites dominated the oceans, when sharks were making their debut,13 and when much of Earth’s land was predominantly in the southern hemisphere, terrestrial plants evolved from aquatic plants and took root along the water’s edge. By 390 million years ago, fish with jaws and fins evolved, some with eyes and some without. They had well-developed spinal columns, jaws with teeth, and pectoral and pelvic fins suitable for swim control. Within another ten or so million years, bottom-dwelling fish began to use their pectoral fins to push themselves along the bottom of plant-thick, shallow, fresh and brackish waters. Getting enough oxygen became a problem for fish living in waters that became oxygen-depleted. 

 

 

Venturing onto Land

The next adaptations enabled them to supplement their gills by taking in oxygen from the air with a primitive lung organ associated with, and perhaps evolved from, the gills. Sturdy pectoral fins enabled them to “walk” over land to escape water-bound predators, and to partake of the insects, plants, worms, snails, invertebrates and segmented body creatures that had already adapted to living on land. A fish that succeeded in transitioning to living on land was Tiktaalik. Apparently, Tiktaalik adapted to living in shallow water by the trial and error process of evolving its fins, head articulation and other features into forms that increased its likelihood of survival. It had basic wrist bones, finger-like features and eyes on top of its flat head. It appears to have had primitive lungs in addition to gills, and a strong rib cage that made possible the transition to living on land without adverse gravitational effects on its organs. In addition, Tiktaalik had no bony plates in its gill area to restrict side-to-side head movement. It had a neck. These water environment adaptations served Tiktaalik well as it ventured onto land and eventually evolved into reptiles.

 

Within another 10 million years, a shallow water vertebrate, much like a salamander, evolved with complex bony limbs for locomotion and lungs adapted to breathing air. This vertebrate could walk over obstacles in its shallow water environment while breathing air.  By 360 million years ago, strong rib cages evolved to protect vital organs and adapted what were pectoral and pelvic fins into limbs suitable for “walking.”14 These walkers were marine amphibians and the first vertebrates able to sustain terrestrial activity. Although a few of their present day descendants are newts, salamanders, toads, and frogs, one ancient South African amphibian grew to 13 feet in length. The demise of these large amphibians probably resulted from competing with the reptilian branch of the family. 

 

Reptiles evolved a number of adaptations that gave them numerous advantages over amphibians. Amphibian reproduction in water enabled their tiny offspring to move about their environments in search of food and prevented them from dehydrating. Reproducing on dry land was another matter. Amphibian reproduction was accomplished in two stages. When first born, their offspring enjoyed the benefits of a water birth, but, when they were large enough to survive on land, they discarded their aquatic characteristics and acquired appropriate land characteristics. Frogs have a tadpole stage before they become recognizable as frogs. By comparison, reptiles evolved a leathery egg that provided nourishment, prevented dehydration, and protected the developing offspring long enough for them to grow to a size suitable for survival on land. In addition, amphibians lost moisture through their skins and gulped air to breathe. Reptiles evolved moisture-resistant scales and a suction breathing system. Air intake for reptiles was not limited by the size of their mouths, but by the size of their lungs. The limbic brain that reptiles inherited evolved into the more capable reptilian brain with an amygdala and hippocampus. With all their neural improvements, however, they were still driven by instinctive responses and learned emotional behaviors. Other adaptations in leg and foot structure provided reptiles with greater speed in seeking food both at the water’s edge and in the nearby growths of grasses and ferns. 

 

In time, plants evolved into tree ferns that used spores to propagate along the wet margins of land and water. As their roots and other features adapted to more arid conditions, tree ferns propagated inland, taking with them evolving vegetarian animals and their predators. The fossil record shows that by 320 million years ago, when the present continents were all part of the super-continent Pangea, conifers and cycads (pine and palm-like trees called “gymnosperms”) had evolved. As with modern conifers, their seeds are enclosed in cones, but unlike modern conifers, they had soft leaves. Fruit-bearing flowering plants were to evolve later. 

 

Slowly, conifers began to cover the land. Their wind-blown pollen fertilized nearby trees, with seeds appearing a number of months after fertilization. Conifers had no insects that assisted in fertilization. Even so, they were better adapted than tree ferns and in time became the dominant vegetation. Eventually, great conifer forests covered the land. By 300 million years ago, the first flying insects evolved—the first of a number of events that would change the world again. 

 

Early mammal-like reptiles appeared about 280 million years ago and evolved over about 210 million years from egg-laying to marsupial births, and eventually to full-term gestations. Many changes were required to evolve reptiles into mammals. For reptiles to function properly, their body temperatures must be high enough to support the biochemical processes that enable them to function. Without the ability to create and regulate their own body temperatures, reptiles had to wait for the sun to heat their bodies before they could perform effectively. For reptiles to become independent of the sun’s heat they had to produce their own. To do this, reptiles required a number of evolved adaptations.

 

Heat is produced as oxygen combines with hydrocarbons from food. To produce more heat, one must take in more oxygen and food, and combine them rapidly. To take in more oxygen, larger lungs that could be filled and emptied rapidly were required. This would both provide more oxygen to the muscles and make more heat available by speeding digestion. The evolution of a breathing diaphragm made respiration more efficient and, if required, more rapid. To take in more food required better teeth and jaws, better locomotion, and a way to prevent eating from interfering with breathing—a constant supply of oxygen is much more important to high-oxygen-consuming mammals. The evolution of a bone shelf separating the nose from the mouth made it possible to take in oxygen while chewing. Three types of teeth evolved permitting grasping, cutting, and grinding in a precision bite. Finely chewed food is more easily digested and more quickly available for use. With intense predation by reptiles, small size became an advantage as early mammals sought protection by hiding. However, small animals have higher surface areas per unit of body weight. All the effort required to produce heat would be compromised if it could escape readily. In time, efficient insulating pelts evolved from scales, as mammal-like reptiles evolved into mammals. Compared with cold-blooded reptiles, typical contemporary mammals are more agile, more intelligent, able to run faster, and have their all-important higher body temperatures regulated automatically, day and night. Although merely representative, these differences indicate the degree of adaptation mammal-like reptiles experienced as they evolved into higher performing mammals. It took time and good fortune. 

 

About 250 million years ago, before mammal-like reptiles began to evolve, disaster struck the Earth. Although the mechanism is not clear, during a period of perhaps 5 to 10 million years, reef and shallow-water environments were devastated. Over 75 percent of reptiles, over 60 percent of amphibians, 8 of 27 orders of insects, and more than 90 percent of all ocean species became extinct. It’s thought that volcanic eruptions in what is now Siberia and China occurred over a period of at least 600,000 years. Ocean levels dropped, parts of the ocean became depleted of oxygen, and fungal growth suggests widespread terrestrial plant devastation.15 Mass extinctions were not new to the Earth. This extinction was the third to occur. The first occurred about 438 million years ago, about 60 million years after the first vertebrates evolved. The second occurred about 367 million years ago, after plants and arthropods (insects) adapted to living on land. Other mass extinctions followed. The fourth at about 208 million years ago occurred a few million years before mammals evolved. The dinosaur age ended about 66 million years ago with an extinction that cleared the way for the evolution of our early primate ancestors. 

 

During the Triassic period, beginning about 245 million years ago, the super continent Pangea had moved farther north, the percentage of atmospheric carbon dioxide was at least four times what it is today, and the average surface temperature was considerably warmer. It was an excellent time for plants and for animals that ate plants. While conifers were evolving, so too were reptiles. One branch of the lineage became the terror of the oceans when it readapted to aquatic life. The dinosaur branch of the reptile family was enormously successful, both as plant and meat eaters. Two general types of dinosaurs are distinguished by their pelvic structures, those described as lizard-hipped and those described as bird-hipped. Among the adaptations that distinguished some dinosaurs from their reptilian ancestors was the ability to walk and run on their pelvic legs. The dinosaur branch that adapted to flight are the ancestors of modern birds.16 

 

Some contend that fast running dinosaurs had to be warm-blooded. Whether they were warm-blooded or cold-blooded is not clear. Today’s warm-blooded creatures consume energy 12 times faster than cold-blooded creatures, an energy-consumption rate that would have been unsustainable given the dinosaur’s rate of food intake and body size. It’s possible that at least some dinosaurs were warm-blooded, but with lower body temperatures than are possible today. To the extent that dinosaurs did not possess adaptations that mammal-like reptiles evolved, it is not clear how dinosaurs could have achieved high body temperatures. 

 

From about 300 million to 250 million years ago, small dinosaurs evolved into many forms, including the enormous, long-necked, leaf-eating sauropods. While these evolutionary events were taking place, the center of Pangea had moved to the equator. As plant-eating dinosaurs (herbivores) evolved and flourished in a conifer-rich environment, so too did meat-eating dinosaurs in their new herbivore-rich environment. It was the dinosaur’s golden age. But, as meat eaters chased plant eaters through ancient conifer forests, a small change was taking place in plant evolution. It was a change that would alter dramatically the lush environment that supported the assent of the dinosaurs. 

 

By about 200 million years ago flowering plants (angiosperms) evolved. Scientists sequenced the Amborella genome and found conclusive evidence that about 200 million years ago a "genome doubling event" occurred. Some duplicated genes made possible new functions, including the development of floral organs. Some believe that flower petals evolved from leaves. Flowering plants differ from conifers in that their seed is enclosed in fruit. Another difference is that flowering plants rely more on insects than on the wind for pollination. As they coevolved, insects and flowering plants adapted to each other’s shapes or other characteristics. This meant that flowering plants had insect partners capable of delivering pollen to distant plants. Early mammals also played a role in speeding the propagation of flowering plants. Mammals at that time17 were about the size of tree shrews and probably foraged at night to avoid being eaten by small dinosaurs. In addition to eating insects and perhaps other small creatures, these mammals ate flowering-plant fruit and dispersed the seeds with their droppings. 

 

Fertilization in flowering plants was extraordinarily fast. These new genetic traits, together with the coevolution of pollen- and seed-spreading animals, accounted for enormous variety among flowering plants and for their capacity to out-compete and displace conifers in temperate regions. This is not to say that conifers did not evolve as well. Over millions of years of ravaging by dinosaurs, conifers evolved defensive poisons and needle-like leaves. Unfortunately for conifers, they were still slow propagators and less well adapted than flowering plants. As you would expect, where flowering plants displaced conifers they displaced conifer-eating dinosaurs as well.    

 

At about 180 million years ago, Pangea separated near the equator with what would become North America and Eurasia moving north, and South America and Africa moving south. An equally significant change was taking place in the structure of reptilian brains. Additional brain capacity was forming as the neocortex began to grow larger, providing the reptilian brain with improved memory and with the beginnings of a capacity to reason.