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

by Michael Tennesen

  Jan Zalasiewicz, lecturer at the University of Leicester, UK, and author of The Earth After Us, admits that it is hard to compare human and geological timescales. He suggests we make a trip to the Grand Canyon near Flagstaff, Arizona, and look down into the mile-deep chasm, whose strata span 1.5 billion years. “Measured on this scale, our own species would fit into a layer about three inches thick, while our industrial record would be confined to about one-hundredth of an inch,” he says. Such an interval would seem almost instantaneous to a geologist—not much more than a meteor strike.

  But the human population boom, though bad for nature, will be great for future interplanetary geologists. The more specimens, the more chance for fossils, and man has come up with an explosion of specimens in just the last hundred years. Perhaps our best choice is to aim for fossil importance.

  But if you really want your bones to end up in a museum diorama somewhere else in the galaxy, then, as they say in real estate, it’s all about location, location, location. You need to take your final bow down by the seashore or at a river mouth where sediments, soil, and rocks are actively being deposited upon one another, earth upon earth, in layers. For if you sing your final swan song on top of a cliff or a mountain, no matter its dramatic appeal, that’s not good for fossil preservation: there’s too much active erosion. Gradual accumulation or “deposition” of soils, as paleontologists refer to it, layer upon layer on top of your bones, is far better for the preservation of future new fossils than erosion.

  So how might Homo sapiens finish their act, and nature move to center stage? Look at the way Neanderthals did it. It was in the caves at the base of the Rock of Gibraltar, at the tip of the Iberian Peninsula, that the last evidence of the Neanderthals was found. Global temperatures were cooler and a lot of water was locked up in ice, lowering sea levels 80 to 120 meters. This opened up a huge portion of the coastal shelf that today is under the Mediterranean Sea.

  There was plentiful meat and game but not enough water. The end could have come during a summer drought when life was stretched to its limit. In that environment, at that time, rains did not come in summer, and in some years they did not come at all.

  Extinction comes when a species reaches a point when births do not keep up with deaths, and numbers gradually diminish. Such a condition for man may come by the end of the century, when many demographers predict population growth may start to diminish. This could be a great thing: man finally reeling in population growth. But is it cause for celebration, or the beginning of the end? If future populations don’t rein in resource use, then diminishing population growth may be an empty promise.

  In recent years, there have been a number of convocations at major universities and governmental offices on threats to man’s existence. Asteroids and comets always come up, since an asteroid had lots to do with the end of the dinosaurs. An asteroid or comet could do us in, as we learned when scientists turned their telescopes to watch the impact of the comet Shoemaker-Levy 9 on Jupiter in July 1994. The warning for such events may be only a year, and the consequences—had that comet hit Earth—could certainly have taken out our species; but it’s more likely to take only a portion of us, with the rest recovering, as in the years following World War II, in a relatively short time.

  Sudden climate change could do it, but we’ve already survived the Younger Dryas event, as well as the last two glacial epochs, and we’re still kicking. Climate change is more apt to wreak havoc on nature, and nature to wreak havoc on us secondhand. Biological warfare? Runaway nanotechnology? We made it through the Black Plague. Even Native Americans survived conquest by the Europeans.

  Robots armed with some sort of super–artificial intelligence, and smarter than their makers—able to access the world’s knowledge from the cloud—might be amazingly helpful or harmful, depending upon their designers, but are not likely to turn on all of us at once.

  Thermonuclear power has lots of potential. In 2012 the Bulletin of the Atomic Scientists announced that it had moved its Doomsday Clock forward to five minutes to midnight. In 2010 the clock had been pushed back to six minutes to midnight, but it was moved closer again based upon the fact that arms reductions worldwide have stalled, as have efforts to curb climate change. The Bulletin mentioned that we still have over nineteen thousand nuclear weapons, “enough to destroy the world’s inhabitants several times over,” and that many countries are in the process of upgrading their current arsenals. The complexity and resources involved in making these weapons has slowed their spread, but what happens if someone should discover a way to make them from sand—or something similar?

  According to the United Nations Population Division, the median population scenario, often seen as most likely, predicts that by 2050 the world will have 9.2 billion people. That’s up from earlier estimates due to increased fertility in Europe and the United States. In 1800, only two hundred years ago, there were only one billion of us.

  Man is immensely resourceful at extracting our natural resources from the earth. As Charles Mann, author of 1491, says, “It is our greatest natural blessing. Or was our greatest natural blessing.” We are getting close to the end in some vital areas. In the next hundred years, despite improving extraction technologies, we could run out of oil, phosphorus, and perhaps even fertile land. The World Bank predicted in the late twentieth century that most twenty-first-century wars would be fought over water supplies.

  According to UC Santa Cruz professor Jim Estes, “We will either evolve into something new, or we will become a dead end. This Homo sapiens lineage will cease to exist. The key thing is the next fifty to one hundred years; that’s the big question. And what’s the quality of life going to be like for those that live through that period? Beyond that, our ability to forecast is very poor. There could still be humans, as we know them today, fifty thousand years into the future. But certainly a million years into the future . . . we will be gone.”

  But what might hold us back from that inflection point that Georgii Gause described in The Struggle for Existence, where the line plummeted down the other side of the steep rise? The answer is: Don’t go there. Hold back. Stop! But in making that request, we are asking humans to do something that no other species has ever done: constrain its numbers voluntarily. It’s a gargantuan order. Zebra mussels in the Great Lakes, brown tree snakes in Guam, water hyacinth in African rivers, Burmese pythons in Florida—all continue to try to overrun their environments.

  But Charles Mann expresses hope. In a recent article for Orion magazine, he described the conditions of slavery in the eighteenth and nineteenth centuries and how society evolved away from the practice. This was also about the time that Robinson Crusoe, Daniel Defoe’s famous novel, came out depicting Crusoe and his men shipwrecked on an uninhabited island off Venezuela where they learned to live off the land. Defoe made Crusoe an officer on a slave ship, then an honorable occupation. When the book came out in 1719, no one complained. Slavery was accepted then.

  But in a few decades in the nineteenth century, slavery almost vanished. The road to this change in terms of human consciousness is enormous. In 1860, slaves, all told, were the single most valuable assets in the United States, worth about $10 trillion in today’s money. But the tide turned on slavery, though at great cost to individual lives and national finances. The American Civil War killed more than six hundred thousand combatants and wrecked the US economy, but slavery died. And it didn’t just die in the US: in the nineteenth and early twentieth centuries it died in Great Britain, the Netherlands, France, Spain, Portugal, Korea, Russia, China, and quite rapidly in most of the rest of the world. There are still some vestiges of slavery in the world—forced labor, sexual slavery, and indentured servitude—but there are few open markets for slavery, and for the most part, nations don’t thrive on their slaves.

  Another example of a great change of attitude is the rise of women. As the Civil War raged in the US to free the slaves, women were also denied essential rights. In both the North and the South, few wo
men could attend college, hold public office, run a business, or vote. Men dominated women in every society. Voting rights for women were not extended until the first half of the twentieth century in most nations. In the United States, women’s suffrage was achieved gradually, reaching nationwide status in 1920 with the passage of the Nineteenth Amendment to the US Constitution. Today women in the US comprise the majority of the workers and the majority of the voters. And this is the same in many countries all over the world.

  Something similar is now happening with gay, bisexual, and transgendered people. Major legislative and legal changes are being made, and an attitude of acceptance is growing.

  Enormous tidal waves of change are still possible for the human species.

  Stopping man from killing himself will take more than behavioral modification. Like a world of dieters fending off hunger, we would have to push back from the table of reproduction, renounce growth, and limit our use of natural resources in order not to hit that fatal inflection curve—to avoid the catastrophe of nature making those selections for us.

  According to Peter Ward, the University of Washington professor and paleontologist, earth is presently in what he calls the habitable zone, the ideal distance from the sun. Astronomers looking for habitable planets in the galaxy look for those that are similarly distant from their stars. If a planet is too close to the sun, it gets too hot. The surface of Venus is hot enough to cook dinner. If it ever had water, it has evaporated into space. On Mars, all the water is frozen. Both Mars and Venus are outside the habitable zone. The trouble is the habitable zone moves outward with time. This is because our sun grows hotter with age. Under these circumstances, the earth will move outside of the habitable zone in 500 million to one billion years. Life may exist on earth, but it will be microscopic. Mars might be a good bet then. If one can wait. If we last that long.

  Ward thinks that man will survive the distance, “but the animals and plants along for the ride on this planet that we cockily co-opted will not be so fortunate.” The future of the planet may be permeated with episodes in which mankind is every once in a while knocked back to the Stone Age.

  Bill Schlesinger, president of the Cary Institute of Ecosystem Studies, says, “The conditions of our planet are largely determined by the biosphere—the collective action of all the species on earth. These species control the composition of our atmosphere and oceans, the climate, and the total amount of plant production on land and in the sea, upon which we all depend for food, fuel, and fiber. It’s hard to believe we could make it without them.”

  No single cause will take humans out. But multiple causes have a chance. In the end it may be as Douglas Erwin describes the end of the Permian—his so-called Murder on the Orient Express theory—in which a multiplicity of causes created the Permian extinction. Such a multiplicity of causes may have provoked the Cretaceous extinction as well: large reptile herbivores mired in a long-term decline, plus the effects of the Deccan Traps, one of the largest volcanic provinces in the world, about half the size of India. Vincent Courtillot from the Institut de Physique du Globe de Paris says, “It released ten times more climate-altering gases into the atmosphere than the nearly concurrent Chicxulub meteor impact.”

  The sixth mass extinction may also be multicausal, arriving on various tracks, including overpopulation, runaway climate change, unbridled disease, and a planet that runs out of modern man’s necessities.

  Might we live on with nature as robots after uploading our minds? Perhaps. But that’s not as sure a bet as one placed on nature. Nature will survive. Life will continue, though in different forms, different species. Ecosystems will recover and thrive one day as they did before us, with different sets of players, perhaps different sets of rules.

  With the heavy cloak of humankind laid to rest, nature may take one enormous sigh of relief, and then press on, to recover its former glory.

  Acknowledgments

  I HAD A LOT of patient, eloquent, and informed help with this book for which I am truly grateful:

  Tom Schulenberg at the Cornell Lab of Ornithology and Louise Emmons at the Smithsonian let me accompany them and their magnificent crew—Lawrence López, Mónica Romo, Brad Boyle, and Lily Rodríguez—on my first visit to the cloud forests of the eastern Andes. Miles Silman at Wake Forest University let me visit that place again.

  Anthony Barnosky at the University of California, Berkeley, first warned me of the possibility of our own mass extinction, though I would hear others such as the famed anthropologist Richard Leakey say the same.

  Guadalupe Mountains National Park geologist Jonena Hearst led me up a West Texas trail to the Capitan Reef and showed me the fossils from the Permian mass extinction. Harvard’s Andy Knoll and MIT’s Sam Bowring gave it an atmospheric and geological perspective.

  William Schlesinger at the Cary Institute of Ecosystem Studies told me about early life on earth and what part chemistry played in its appearance. Rick Ostfeld, also at Cary, told me how the loss of forest and animal species was a setup for disease. Rob Jackson at Stanford took me down into Powell’s Cave in Central Texas to show how juniper, an invasive plant, was stealing water from the Edwards Plateau.

  Stuart Findlay at Cary helped me understand New York’s Catskill/Delaware Watershed. Dalia Amor Conde of the Max-Planck Odense Center showed me how jaguars and rain forest are vital to human life in Central America. Stan Smith at the University of Nevada, Las Vegas, and Greg Okin at the University of California, Los Angeles, showed me how desert crusts are vital to the longevity of the American desert. The paleontologist Charles Marshall at the University of California, Berkeley, gave me an Australian perspective of US species loss.

  Kevin Coleman and Paul Poulton at Rothamsted Research in the UK described how important our soil is to the future of agriculture. Dan Richter at Duke University took me to my first conference on soil. Eduardo Neves at the Universidade de São Paulo introduced me to terra preta, black earth, an earthy gift from ancient Amazonian Indians.

  Leslea Hlusko at the University of California, Berkeley, and Jackson Njau at Indiana University let me share their field site at Olduvai Gorge in Tanzania. Miriam Ollemoita took me to her Maasai village. And Tomos Proffitt entertained me by making Stone Age hand axes.

  Hans-Dieter Sues at the Smithsonian explained how crocodiles were the real dominant predator during the Triassic. Rick Potts, also at the Smithsonian, talked of the role climate may have had in the development of early man. Kathy Weathers at Cary turned me on to the fog forests of eastern Chile.

  Thanks to Jim Estes at UC Santa Cruz for helping me understand how killer whales could turn to sea otters for food; to William Gilly at Stanford for all the time he spent teaching me about Humboldt squid; to Gretchen Hofmann at the University of California, Santa Barbara, for her insight on ocean acidification; and to Frank Hurd for his tireless efforts to bring clean, sustainable aquaculture to the natives of Baja California to make up for the disappearing fish.

  Felisa Smith at the University of New Mexico showed me how animals once got very big, and how they might get there again. Blaire Van Valkenburgh at UCLA showed me how vital and diverse nature once was four miles south of Hollywood.

  Henry Harpending at the University of Utah convinced me that man is still evolving. And Oxford’s Nick Bostrom delighted me with his predictions of the future of man on earth.

  Stephen W. Smith at Duke University, author of sixteen books, was my mentor throughout, encouraging me to write faster and encouraging me to go to Africa. Thanks to Jim, Julie, Noel, Eddie, Geary, and the other members of the Sky Valley hiking club with whom I spent many mornings and whose questions kept me thinking. Thanks to my other writer friends, Susan Squire, Stewart Weiner, and Susan Vreland, for all their sage advice.

  I owe a lot to my family, Bill, Barbara, Sam, Ann, Marguerite, and my wife, Maggie, for putting up with me during this long process. Also to Mike LaJoie, Alex Wexler, Grace Murphy, and Gary Kott for their invaluable support.

  Thanks to J
ud Laghi for the fire and enthusiasm he displayed in representing me. Also to Hilary Redmon, who first saw the promise in it. Thanks also to Leah Miller, Webster Younce, and Karen Marcus for herding me through the early days, and Sydney Tanigawa, editor extraordinaire, who helped me wrangle a sometimes disjointed manuscript into its present form.

  Thank you all.

  © MARTIN COX

  MICHAEL TENNESEN is a science writer who has written more than three hundred stories in such journals as Discover, Scientific American, New Scientist, National Wildlife, Audubon, Science, Smithsonian, and others. He was a Writer in Residence at the Cary Institute of Ecosystem Studies in Millbrook, New York, and a Media Fellow at the Nicholas School of the Environment and Earth Sciences, Duke University. He lives in the California desert near Joshua Tree National Park.

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  Notes

  Prologue WE HAVE NO IDEA WHAT WE’RE IN FOR

  It was mid-morning, June, during the tropical dry season: Michael Tennesen, “Expedition to the clouds,” International Wildlife (March/April 1998), 22–29.