The Next Species: The Future of Evolution in the Aftermath of Man

by Michael Tennesen

  Though the asteroid that got the dinosaurs at the Cretaceous extinction may have produced a better fireworks display and spectacular tsunamis, in terms of pure raw killing power, the Permian extinction can’t be beat. Its witch’s brew of toxins poisoned the land for several hundred thousand years. Doug Erwin says that the eruption of the Siberian Traps caused global cooling from the erupted dust, global warming from the CO2, and acid rains from billowing clouds of sulfur. Couple this with ocean acidification and the death of oxygen in the deep seas due to the melting of polar ice and the loss of ocean currents, and you have a lethal force that far exceeded the destruction caused by the falling asteroid during the Cretaceous.

  The resulting excess CO2 entered the ocean, making the water acidic enough to prevent animals from forming exterior skeletons and destroying most of the reef-making organisms of the Permian seas and most of the reefs. The acidic nature of the seawater, coupled with the lack of oxygen in the deep oceans, wreaked havoc on marine plants and animals. The sulfates that emerged from the volcanoes reached the upper atmosphere, to be carried afar as sulfuric acid and lethal acid rains. These rains may have been strong enough, suggests Erwin, to kill off many of the terrestrial plants. This totally denuded landscapes over much of the earth’s surface. Scientists have found evidence that much of the rain that followed the Permian extinctions rolled off the land in flash floods, since there was no vegetation to contain the flow of water.

  Floods skipped across the earth like oil does on a hot skillet, moving in every direction, leaving braided gullies in the rock record. I’ve witnessed fast-moving desert flash floods that carved out chunks of road like butter, but desert rains are meager. Imagine flash floods raging in plant-free tropical or coastal environments where annual rainfalls are twenty, fifty, one hundred inches, or more, racing in full and furious force across landscapes stripped of vegetation, and you’ll get an idea of what the floods that followed the Permian extinction must have been like.

  But despite the evidence of multiple causes for the Permian extinction, some scientists still champion their favorite antagonists. Andrew Knoll, a paleontologist at Harvard, thinks that many of the catastrophes—their causes and their results—can be boiled down to one chemical compound, CO2, the biggest villain of the day, and perhaps our greatest threat as well. In a 2007 paper in Earth and Planetary Science Letters, Knoll and colleagues tried to work backwards from the extinction event, doing a computerized autopsy of the victims to see if the massacre matched the typical scenario caused by oxygen depletion, a breakdown of the food web, and acid rains, but none of them quite matched the autopsy except for CO2. He highlighted a gas that so many today ignore. “Only 30 percent of the species of plants and animals were tolerant of massive doses of CO2. But after the Permian extinction, that 30 percent suddenly becomes 90 percent of all living animals.”

  Estimates vary on how long this extinction lasted. MIT’s Sam Bowring sets the duration at about sixty thousand years. The tiny chewing apparatuses of small eel-like animals are some of the first fossils to appear in layers of earth laid down after the Permian extinction. Fossils of Lystrosaurus, a mammal-like reptile that looked like a bulldog with tusks, but which survived the extinction and proliferated, mark the beginning of the Triassic recovery.

  The irony of the Permian extinction is that though it devastated large portions of the planet, it created opportunities in newly emptied terrain. From the resurrection of life after the mass annihilation of the Permian came more-adaptive species, changes in ecosystems, and a world more diverse than the one before it. Perhaps these improvements could be in our future—if we survive the extinction.

  The processes were similar to what Darwin witnessed in the Galápagos Islands. Of the twelve species of finches he collected, all were adapted from a few individuals from the mainland or other islands, which had arrived in the Galapágos and proliferated after finding no competition for the banquet of seeds available.

  What emerged from the Permian extinction was a similar explosion of new animals and plants. Life not only survived, it eventually thrived. By 225 million years ago, the first dinosaurs appeared; but by 65 million years ago the group, other than birds, was gone. Their reign on earth lasted close to 160 million years, a length of time that the family of man has barely approached.

  Though the end was glorious, the millions of years it took to recover from the Permian extinction were excruciating.

  After a brief lunch at the end of the trail, looking out over western Texas and southeastern New Mexico, enjoying the cooler breezes at the top of the range, Hearst and I gathered our gear and headed back down the same path we’d come up on, still taking note of the various changes in the fossil communities, enjoying a second look, knowing them better.

  Hearst explained that life as a whole eventually resurrected itself from the Permian extinction, but few of the individual species of plants and animals displayed here in the fossils of the mid-Permian made it across the boundary. “Life goes on. Life is incredibly resilient. But my work here has taught me that ecosystems and individual species are so very, very fragile,” she said. If history is our teacher, then life in the aftermath of our own era will prove equally resilient, though right now ecosystems and individual species are rapidly disappearing.

  From the height of the trail we looked out over the vast desert below and reflected on our own situation. We stood in the middle of evidence of a past evolutionary catastrophe and gazed out over another in progress: our own. Some scientists believe our current situation started at the onset of the Industrial Revolution in Great Britain during the 1700s. This is when CO2 in the atmosphere began its upward climb, a change mirrored here in the aftermath of the Permian. But others date the commencement of our dilemma to 1800, when the human population reached one billion.

  Still, others say we entered the present biodiversity crisis during the final moments of the last ice age from about fifteen thousand to twelve thousand years ago, when a substantial portion of the large animals that once existed in North and South America disappeared. Similar scenarios took place in Australia, New Zealand, Europe, and Asia with the arrival of man.

  Hearst poured some water on a group of fossils, washing off the dust and making them more defined and lifelike for the moment. Of course, the evolutionary processes that produced their first spark of life were much more complicated.

  2

  ORIGINAL SYNERGY

  IT HAD BEEN RAINING off and on all week at the Cary Institute of Ecosystem Studies in Millbrook, New York, a reserve consisting of two thousand luscious acres of mid–Hudson Valley oak, maple, and hemlock that the institute refers to as its “campus.” I had some big questions to ask—how life got started, how evolution drove its development, what role oxygen played, if evolution was still at work in the natural world—and I began my quest at Cary.

  A heavy mist rose that day from the wetland patches and crept through the forest propelled by a Sunday morning sun. William H. Schlesinger, biogeochemist and president emeritus of the institute, and his wife, Lisa Dellwo, guided me on a birding expedition during a break in the rain through the woods and meadows that abound there. We spotted seventy-six birds before breakfast, sixteen species in all. When I couldn’t see a bird, they both went to extremes to describe the bird and the place in the woods where it was. Lisa claimed birding cultivates cooperation and communication, and is sadly overlooked as executive training.

  On the way back from the woods, I got to talk to Schlesinger about life. Bill is a tall, burly man with a hearty laugh, a deep, articulate voice, and a head full of chemical formulas. He thinks chemistry is often underrated and coauthored a book called Biogeochemistry: An Analysis of Global Change with Duke University’s Emily S. Bernhardt. The book looks at the role of biology, geology, and chemistry in changes that have occurred on earth.

  “The road to life on planet Earth was peppered with more chemistry than people give it credit for,” Schlesinger told me.

  Though our galaxy,
the Milky Way, has existed for 13.7 billion years, our solar system is only about 4.6 billion years old. Our sun, said Bill, is at least a second-generation star—a descendant from a prior supernova, a large star that ran through its nuclear fuel, collapsed, and then exploded. That explosion blew a whole lot of dust and particles into the cosmos, and the sun and Earth coalesced out of that cosmic residue. A heavy meteor bombardment ensued during the first billion years, added to Earth’s mass, and created its moon. The heat of the collisions and the radioactive decay of the materials melted the whole ball with the heavier chemicals sinking to the molten core, while the lighter elements formed the semifluid mantle and the crust that floats upon it.

  One of the critical components for life, Bill pointed out to me, was plenty of water. At the Cary Institute, it had just rained, and we jumped around puddles and dodged the occasional deluge delivered from the leaf canopy above while Schlesinger explained how we got all this moisture. Schlesinger is an excellent orator and teacher, one who is not afraid to hold forth until he sees the light in your eyes that tells him you got it.

  Water probably came from the same bombardment of materials that built the planet, he suggested. The heat of the planet would have kept that fallen moisture as steam in the atmosphere until the Earth’s surface cooled to 212 degrees Fahrenheit (100 degrees Celsius), the boiling point of water. Afterward, the steam coalesced and the moisture fell out of the sky over several million years, filling the oceans.

  The sun was then 30 percent less luminous than it is today, but the presence of water vapor and CO2 in the atmosphere produced a greenhouse effect, catching any escaping infrared or heat radiation and redirecting it back toward the surface of the Earth. This warmed the planet. Without the greenhouse effect, the Earth today would be mostly covered with ice and have an average temperature of about 0 degrees Fahrenheit (minus 18 degrees Celsius).

  Another gift of the early arrival of celestial materials on Earth was carbon, a critical element of life. “All life on this planet is made of compounds that have carbon in them,” said Schlesinger. Carbon forms strong bonds with other chemicals, which is important for building long chemical structures like proteins, cellulose, and DNA. “If you took your body, dried all the water out of it, what’s left would be about 50 percent carbon,” he said. “We are basically bags of carbon running around on the surface of the Earth.”

  How did we get life from carbon molecules? Where did it first occur? These have not been easy questions to answer. Some interplanetary dust and comet ices are found to contain organic matter containing carbon and could have survived entry into Earth’s atmosphere, adding to the carbon already here, he says. Even if the total amount of organic comet matter received by Earth was small, these elements could have served as a catalyst for life.

  Scientists and philosophers have debated the question of first life for millennia, though most of the explanations have centered on fable or religion. In 1929, British biochemist J. B. S. Haldane and Soviet scientist Alexander Oparin independently suggested that all the ingredients for life existed on Earth from the beginning and that energy from the sun and some unknown process had gotten life started. In the 1950s, Stanley Miller, a doctoral student in the laboratory of Harold Urey, at the University of Chicago, got more specific when he attempted a famous experiment. He mixed ammonia, methane, and hydrogen—a commonly accepted recipe for the early atmosphere and ocean—in a big laboratory flask and subjected it to an electric charge that simulated lightning. He analyzed samples at regular intervals. The result was a jackpot for Miller and the Urey lab: after about a week he found simple organic molecules in the flask. Life could be produced in a laboratory. He had cooked the infamous primordial soup.

  But fame was fleeting. Miller had fashioned his recipe after Jupiter and some of the outer planets, but those models proved to be an inaccurate representation of early Earth. More realistic versions didn’t do as well, either, and the idea that you could cook up life like soup fell out of favor.

  But if soup didn’t initiate life, then what did? Scientists turned to the oceans for answers.

  Possible solutions emerged in the early 1970s when scientists noticed rising plumes of warmish water along a deep ocean crack near the Galápagos Islands, the same islands that fostered Darwin’s theory of evolution. In 1977, the US naval submersible Alvin dove down 7,000 feet (2,100 meters) to investigate deep-ocean geysers and found a wonderland of giant clams and mussels as well as eight-foot-long tubeworms. The sheer abundance of life at that depth was astonishing—a tropical rain forest of ocean species. Here, eyeless shrimp and snails munched on mats of bacteria that thrived on sulfur compounds. These underwater geysers generated supplies of energy for the plants and animals, rather than the sun, whose light didn’t reach this depth.

  Scientists have since explored over two hundred of these geyser systems in the oceans. Some of the most remarkable have been along the deep-ocean ridges of the Pacific, Atlantic, and Indian Oceans. At these ridges, the seafloor spreads outward along a rift fed by hot magma below, the birthplace of new land on earth. At such places, researchers found colossal deepwater chimneys known as black smokers, some as tall as skyscrapers, pumping what appeared to be billowing black smoke into the sea. It wasn’t real smoke, of course, but boiling metal sulfides welling up from the magma below, the acidic mixture oozing into the water at 662 degrees Fahrenheit (350 degrees Celsius).

  Was this eerie place with its bizarre cast of characters where life originated? Though boiling sulfides hardly sounded like a Sunday buffet, there were certain advantages. The ocean depths would have shielded life from the UV radiation that was then pummeling the ocean surface as well as the land a few billion years ago. Michael Russell at NASA’s Jet Propulsion Laboratory in Pasadena, California, thought the mixture too acidic to be involved. So he came up with a theory for a milder first-life solution by looking for another type of geyser that had a gentler origin.

  His theoretical answer arose from the slower movement of fresh crust across the seafloor, exposing rocks from the mantle. Russell’s candidate for the prime mover wasn’t an acidic mixture of superheated waters; it was the reaction of freshly exposed rock with seawater at a relatively cooler 210 degrees Fahrenheit (100 degrees Celsius).

  Seawater expanded the rock, creating fissures and cracks, which drew in still more seawater. This process released energy as heat and large amounts of hydrogen and methane gas. This created another type of hydrothermal geyser, which some called white smokers, or more accurately alkaline vents. Rather than creating a black chimney with a single orifice belching black superheated smoke, these vents were complex structures with mazes of tiny compartments that exuded warm alkaline water to the surrounding cold seawater.

  Life could have arisen from sulfidic submarine hot springs situated some distance from the deep oceanic ridges. Scientists thought that four billion years ago life could have emerged there from a mass of bubbles, each bubble containing hot mineral-laden solutions.

  Around the turn of the twenty-first century, the research vessel Atlantis and its human-occupied submersible Alvin found this exact type of geyser about nine miles (fifteen kilometers) from the Mid-Atlantic Ridge. Dubbed the Lost City, these vents stood like ornate structures up to two hundred feet (sixty meters) in height, poking up into the vast darkness. At this depth hydrogen could more freely bind to carbon dioxide to form organic molecules. First life was not a single cell but a rocky labyrinth of mineral cells that produced complex molecules, including the formation of proteins and eventually DNA molecules, generated by the energy of the warm vent fluids.

  As we came to the end of our bird walk at Cary, Schlesinger said that this made sense. He had one caveat: he favored a more neutral solution for first life. “Life can tolerate a wide range of pH, but really acid conditions [low pH] are likely to oxidize organic materials and really alkaline conditions break down cell membranes,” he explained.

  OXYGEN MAKES IT HAPPEN

  Most scientists agree t
hat, for the first few billion years, life was largely microbial. Yet these little critters were responsible for most of the genetic heavy lifting. Though we marvel at the size and anatomical complexity of large animals, these features were made possible by cell biology and genetics that were developed in single-cell creatures in much earlier times. According to Harvard’s Andy Knoll, when complex life first evolved, it had the majority of its DNA already worked out.

  For life to really get going, to produce the complex forms of more evolved beings, it had to have oxygen. Two and a half billion years ago, “life” was still in bacterial forms. It had its genetic architecture, but it survived in oxygen-free environments, so it stayed small. But then some of the oxygen-free bacteria evolved into cyanobacteria or blue-green algae, the stuff you sometimes see on polluted waters, commonly referred to as “pond scum.”

  These guys promoted photosynthesis, a different type of metabolism from what their archaic brethren employed. Photosynthesis used sunshine, water, and carbon dioxide to produce carbohydrates and, finally, oxygen. At last, the giraffes and basketball players of the world had a chance at survival!

  Oxygen was the critical element in the burst of evolution that occurred during the Cambrian explosion about 570 to 530 million years ago, when most of the major animal groups suddenly appear in the fossil record. At the time the air was murky, since there wasn’t enough oxygen to scrub the atmosphere of haze and dust. Without enough oxygen, there was no ozone, either, so the searing intensity of ultraviolet light from the sun could fall without obstruction. Ultraviolet light breaks up water (H2O), and since hydrogen (H) is so light, it can slip into space, and there goes your ocean. Without oxygen holding on to hydrogen, the world today might look a lot like Mars: a dry, dusty, pockmarked planet with no seas, lakes, rivers, or streams and no visible sign of life.