Scatter, Adapt, and Remember: How Humans Will Survive a Mass Extinction

by Newitz, Annalee

  “Adaptability” is a term you hear a lot from people who study mass extinction. They talk about it with a weird, gallows-humor kind of optimism. This is evident when you meet Earth scientist Mike Benton, who has spent the past ten years studying the Great Dying and its survivors. In his line of work, Benton has sifted through the remains of some serious planetwide horrors. Two hundred and fifty million years ago, when the Great Dying happened, megavolcanoes fouled the atmosphere with carbon, and it’s possible that an asteroid hit the planet, too. Despite Benton’s intimate familiarity with mass death, he still maintains hope that our species will survive. He told me that “good survival characteristics for any animal” include being able to eat a lot of different things and live anywhere, just as humans can. Of course, he noted, that doesn’t mean there won’t be a lot of casualties. He continued:

  Evidence from mass extinctions of the past is that the initial killing is often quite random, and so nothing in particular can protect you, but then in the following grim times, when Earth conditions may still be ghastly, it’s the adaptable forms that breed fast and live at high population size that have the best chance of fighting through.

  We have a fighting chance because our population is large, plus we can adapt to new territories and eat a wide range of things. That’s a good start, but what does it really mean to fight through? In part three of this book, we’ll look at some specific examples of how humans and other creatures have used the three survival strategies of scattering, adapting, and remembering. We’ll also explore how humans survive by planning for the future through storytelling. Fiction about tomorrow can provide a symbolic map that tells us where we want to go.

  Stories of the Future

  So where, exactly, do we want to go? With parts four and five, we’ll launch ourselves into humanity’s possible future. One of our biggest problems as a species today is that we have become so populous that our mass societies are no longer adaptive. Over half the population lives in cities, but cities can become death traps during disasters, and they are breeding grounds for pandemics. Worse, they are not sustainable; cities’ energy and agricultural needs are outpacing availability, which limits their life spans and those of the people in them. Part four is about several ways we’ll want to change cities over the next century to make them healthy, sustainable places that preserve human life as well as the life of the environment.

  Often, a city-saving idea can start in a lab. Right now, in a cavernous warehouse on the Oregon State University campus, a group of researchers is designing the deadliest tsunami in history. In this cold, windy laboratory, they’ve got a massive water tank, about the size of an Olympic swimming pool, whose currents are controlled by a set of paddles bigger than doors. In the tank, wave after wave buffets a very detailed model city, washing away tiny wooden houses. Whirling in the water are special particles that can be tracked by hundreds of motion detectors, which help scientists understand tsunami behavior. At the tsunami lab, civil engineers destroy cities to figure out the best places for flood drains and high-ground emergency pathways in coastal cities.

  Thousands of kilometers across the country, a revolutionary group of architects is working with biologists to create materials for “living cities” that are environmentally sustainable because they are literally part of the environment. These buildings might have walls made from semipermeable membranes that allow air in, along with a bit of rainwater for ceiling lights made from luminescent algae. Urbanites would grow fuel in home bioreactors, and tend air-purifying mold that flourishes around their windows. Unlike today’s cities, these living cities will run on biofuels and solar energy. These are the kinds of metropolises where we and our ecoystems could thrive for millennia.

  In part five, we’ll look to the far future of humanity and think about our long-term plan to keep our species going for another million years. We know that when early humans were threatened with extinction they fanned out across Africa in search of new homes, eventually leaving the continent entirely. This urge to break away from home and wander has saved us before and could save us in the future. If we colonize other planets, then we will be imitating the survival strategy of our ancestors. Scattering to the stars echoes our journey out of Africa—and it could be our best hope for lasting through the eons.

  Engineers at NASA are already preparing more robotic missions to the Moon, nearby asteroids, and Mars, hoping to learn about how the water we’ve discovered on other worlds could sustain a human colony. Every year since 2006, an international group of scientists and entrepreneurs holds a meeting in Washington State to plan for a space elevator that they hope to build in the next few decades. Such a project would allow people to leave Earth’s gravity while using a minimum of energy, thus making travel off-world more economically feasible (and less environmentally damaging) than with rockets. Other groups are figuring out ways to reengineer our entire planet to slow the release of greenhouse gases and grow enough food for our booming population.

  These projects, designed to improve cities on Earth while paving the way for life on other worlds, are just a few examples of how humans are getting ready for the inevitable mega disasters that await us. They are also powerful evidence that we want to help each other survive.

  Human beings also have one survival skill that we’ve yet to find in creatures around us. We can pass on stories of how to cope with disaster and make it easier for the next group who confronts it. Our tales of survival pass over borders and travel through time from one generation to the next. Humans are creatures of culture as well as nature. Our stories can offer us hope that we’ll make it through unimaginable troubles to come. And they can inspire scientific research about how we’ll do it. Call them tales of pragmatic optimism.

  This book is full of such tales—stories about people whose pragmatic optimism could one day save the world. Scientists, philosophers, writers, engineers, doctors, astronauts, and ordinary people are working tirelessly on world-changing projects, assuming that one day our lives can be saved on a massive scale. As their work comes to fruition, our world becomes a very different, more livable place.

  If humans are going to make it in the long term, and preserve our planet along with us, we need to accept that change is the status quo. To survive this far, we’ve had to change dramatically over time, and we’ll have to change even more—remolding our world, our cities, and even our bodies. This book is going to show you how we’ll do it. After all, the only reason we’re here today is because thousands of generations of our ancestors did it already, to make our existence possible.

  PART I A HISTORY OF MASS EXTINCTIONS

  A timeline of mass extinctions, including Snowball Earth. (illustration credit ill.1)

  (Click here to see a larger image.)

  1. THE APOCALYPSE THAT BROUGHT US TO LIFE

  IF YOU THINK that humans are destroying the planet in a way that’s historically unprecedented, you’re suffering from a species-level delusion of grandeur. We’re not even the first creatures to pollute the Earth so much that other creatures go extinct. Weirdly, it turns out that’s a good thing. If it hadn’t been for a bunch of upstart microbes causing an environmental apocalypse over 2 billion years ago, human beings and our ancestors never would have evolved. Indeed, Earth’s history is full of apocalyptic scenarios where mass death leads to new kinds of life. To appreciate how these strange catastrophes work, we’ll have to travel back in time to our planet’s beginnings.

  The Proterozoic Eon (2.5 billion–540 million years ago): Oxygen Apocalypse

  Earth is roughly 4.5 billion years old, and for most of its life the atmosphere would have been noxious for humans and all the creatures who live here now. Vast acidic oceans roiled in what today’s environmental scientists would call an extreme greenhouse climate: the air was superheated and filled with methane and carbon. Our planet’s surface, now covered in cool water and crusty soil, was bubbling with magma. The solar system had formed relatively recently, and chunks of rock hurtled between th
e young planets—often landing on them with fiery explosions. (One such impact on Earth was so enormous, and threw off so much debris, that it formed the Moon.) It was on this poisonous, inhospitable world that life began.

  About 2.5 billion years ago, early in an eon that geologists call the Proterozoic, a few hardy microbes who could breathe in this environment drifted to the surface of the oceans. These microbes, called cyanobacteria (or blue-green algae), knit themselves into wrinkled mats of vegetation. They looked like black, frothy coats of slime on the water, trailing long, feathery tendrils beneath the waves. All that remains of this primordial ooze are enigmatic fossils that hide inside a distinctive type of ancient, spherical rock called a stromatolite. If you slice a stromatolite down the middle, you’ll see thin, dark lines curving across its inner surface like the whorls in a fingerprint—these are all that remain of those algal mats. Only a few people in the world would recognize them as the traces of impossibly old life that they are, and Roger Summons is one of them. He’s a geobiologist at the Massachusetts Institute of Technology who has spent decades studying the origins of life on Earth, as well as the extinction events that wipe it out.

  An Australian with a dry sense of humor, Summons has an office you can only reach by walking through his lab, a big, airy room full of tanks of hydrogen and bulky mass spectrometers that look like old-school Xerox machines covered in tubes. When I visited him to talk about ancient Earth, he plucked some slices of stromatolite from the top of a filing cabinet to show me the traces of algae that spidered across their surfaces. “This one is eight hundred million years old, and this one is two-point-four billion,” he said, pointing at each ragged half sphere of rock. “Oh, and this one is probably three billion years old, but it’s a crap sample.”

  Even with a “crap sample,” Summons can pin a date on the fossils of creatures who lived more than 2 billion years ago by examining the sediments that have preserved them. In his lab, researchers grind up ancient rocks, subjecting them to vacuum, freezing, lasers, and a strong magnetic field before running them through the mass spectrometers. At that point, often nothing remains of a stromatolite but ionized gas. And that’s exactly what mass spectrometers need to decode the atoms in each sample. Atoms in minerals decay at a fixed rate, and reading the state of a rock’s atoms can tell scientists how long it has been since it formed. Geologists don’t put fossils themselves beneath the laser. They use machines like the ones in Summons’s lab to figure out the ages of the rocks next to the fossils. Call it dating by association.

  Knowing when the oldest stromatolites were created helps us date an event which changed Earth forever. The mats of algae that became stromatolites weren’t just methane-loving scum. They were also filling the atmosphere with a gas that was deadly to them: oxygen. This is how the first environmental disaster on Earth began.

  Just like plants today, ancient blue-green algae nourished themselves using photosynthesis, a molecular process that converts light and water into chemical energy. Cyanobacteria were the first organisms to evolve photosynthesis, and they did it by absorbing photons from sunlight and water molecules from the ocean. Water molecules are made up of three atoms—two hydrogen atoms and one oxygen atom (hence the chemical formula H2O). To nourish themselves, the algae used photons to smash water molecules apart, taking the hydrogen to use as an energy source and releasing the oxygen molecules. This proved to be such a winning adaptation to Earth’s primordial environment that cyanobacteria spread across the face of the planet, eventually exhaling enough oxygen to set off a cascade of chemical processes that leached methane and other greenhouse gases from the atmosphere. The dominant form of life on Earth ultimately released so much oxygen that it changed the climate dramatically, soon extinguishing most of the life-forms that thrived in a carbon-rich atmosphere. Today we worry that cow farts are destroying the environment with methane; back in the Proterozoic, it’s certain that algae farts ruined it with oxygen.

  Greenhouse Becomes Icehouse (and Vice Versa)

  What happened after the rise of oxygen was an event shrouded in mystery until the late 1980s, when a Caltech geologist named Joe Kirschvink asked his student Dawn Sumner to research a rock whose existence seemed to be impossible—at least, given the prevailing theories about early Earth. Found near the equator, the rock’s surface was scored with marks that suggested it had once been scraped by the weight of a slow-moving glacier. In a short paper that eventually revolutionized geologists’ understanding of climate change, Kirschvink suggested that this rock offered a window on a late-Proterozoic phenomenon he called Snowball Earth.

  Snowball Earth is what happens when our planet’s climate enters a very extreme “icehouse” state, the opposite of a greenhouse. A carbon-rich atmosphere can heat our climate up into a sweltering greenhouse, but an oxygen-rich atmosphere cools it down and causes what’s called an icehouse. Throughout its life, the planet has vacillated between greenhouses and icehouses as part of a geological process called the carbon cycle. Put in the simplest possible terms, a greenhouse happens when carbon is free in the air, and an icehouse occurs when carbon has been locked down or sequestered in the oceans and rocks. During an icehouse, ice collects at the poles, sometimes creeping down into lower latitudes during an ice age. But our recent ice ages were nothing compared with Snowball Earth.

  Two billion years ago the sun was dimmer than it is today. As more and more cyanobacteria pumped out oxygen, the whole place began to cool down. Because the sun was a relatively weak heat source, this effect was magnified into a “runaway icehouse.” Ice from the poles began to spread outward, solidifying the top layer of the oceans and burying the land beneath vast, frozen sheets. The more ice that formed, the more it reflected sunlight—lowering the planet’s temperature further. Finally, ice stretched from the poles nearly all the way to the equator, pulverizing rocks beneath its weight. If you looked at Earth from space at that time, you’d have seen a slushy white ball, its circumference banded by a narrow equatorial ocean of algae-infested sludge. At that moment in geological history, our planet resembled Saturn’s icy moon Europa. It was an alien world called Snowball Earth.

  I visited Kirschvink at the California Institute of Technology to find out what happened next. In the basement of the geology building, his generously sized desk was piled with fossils, family photographs, papers, and his prized possession, a cheap plastic vuvuzela from South Africa. “This is real!” he enthused, gesturing at the instrument whose droning sound annoyed and delighted audiences during the 2010 World Cup. Kirschvink lit up when he talked about the provenance of objects, whether pop culture ephemera or 3-billion-year-old fossils. Maybe it was his off-kilter imagination that allowed him to look for environmental patterns in Earth’s history that nobody had thought possible.

  Kirschvink believes that there may have been as many as three snowball phases on Earth. “It was the longest, weirdest perturbation in the carbon cycle,” Kirschvink said. “And my explanation for it is simple. It’s the time between when the biosphere learned to make atmospheric oxygen and the time when everybody else learned to breathe it and use it.” Without any creatures around to breathe oxygen, the cyanobacteria likely created an atmosphere far more oxygenated than any we’ve ever known.

  For 1.5 billion years after cyanobacteria evolved, Earth’s biosphere was in chaos. At least two more snowballs crept across the face of the planet, followed by intensely hot greenhouse conditions caused when volcanoes pumped carbon back into the air. Meanwhile, microbes were slowly learning to use oxygen to their advantage. A new kind of cell called a eukaryote began to populate the seas. Unlike cyanobacteria, which are basically just genetic material contained inside a membrane, a eukaryotic cell contains a nucleus packed with DNA as well as tiny organs called, appropriately enough, organelles. One of those organelles, called a mitochondrion, could turn free oxygen and other nutrients into energy. At last, Earth was inhabited by oxygen-breathers. The planet we know today was taking shape.

  While the eukar
yotes got busy swapping genetic material and sucking oxygen from the air, the old methane-breathers were dying out. A few migrated to the sea floor, finding niches near superheated volcanic vents where they could live in the remaining fragments of a once-global methane ecosystem. But the rest went extinct. It was the most extreme form of atmospheric pollution in Earth’s history, soon killing off almost every form of life that couldn’t breathe oxygen.

  By “soon,” I mean within a billion years, or possibly 2 billion—a period of time that’s almost impossible to wrap our minds around. Still, that is the timescale required to understand Earth’s environmental transformations. Many of the catastrophic changes we’ll discuss over the next few chapters took millions of years to unfold. To geologists, we are all living in fast motion, our lives so short that it’s usually impossible for us to personally experience environmental change. Often, these scientists will contrast “human-scale” time with what they clearly view as real time, or time that unfolds on a planetary scale.

  One of our most incredible accomplishments as a species, however, is an ability to think beyond our own life spans. We may not live in geologic time, but we can know it. And the more we learn about our planet’s past, the more it seems that Earth has been many different planets with dramatically different climates and ecosystems. This idea offers a much broader perspective than what you find in the work of environmentalists like Bill McKibben, who argues in his book Eaarth that humans have burned so much fossil fuel that we’re turning our planet into something fundamentally different (requiring the new name Eaarth). In that book and elsewhere, he laments the loss of “nature,” by which he means the ecosystems that existed on Earth before human meddling. But before humans took center stage on Earth, there were many permutations of nature. Climate disasters were the norm. Indeed, the only way Earth could ever transform enough to merit a new name like Eaarth would be if the planet’s environment suddenly stopped changing.