While it can sometimes seem like humanity is hell-bent on environmental destruction, it’s unlikely our actions will end all life on Earth. Some creatures are sure to endure in this age of mass extinction and climate crisis. Over time, they will adapt to a harsher world we’ve helped create, evolving to meet the moment as best they can.
Some of these transformations have gotten underway in our lifetimes. Climate change, some research suggests, is already “shape shifting” animals — shrinking certain migratory birds and speeding up the life cycles of amphibians, for example. No one knows exactly what changes to plants and animals will transpire in the years to come. Still, evolutionary biologists say it’s worth trying to imagine what creatures will evolve in the future.
“I do think it’s a really useful and important exercise,” Liz Alter, professor of evolutionary biology at California State University Monterey Bay, says on the latest episode of Unexplainable, Vox’s podcast about unanswered questions in science. In thinking about the animals of the future, Alter says, we must consider how we’re changing the environment now. “It’s a very sobering thing to think about the long future,” she says.
I spoke to several evolutionary biologists and paleontologists who, along with Alter, helped me imagine what animals might exist one day — say, millions of years into the future — and how our actions could spur their arrival. At the very least, it’s reassuring to know that life almost certainly will find a way, with or without us.
But it may never be the same.
Animals that might make it
What animals are likely to exist tens of thousands, or even millions of years from now?
That’s the big question I posed to everyone I spoke with, and their responses fell along three main lines of thinking.
Some started off by thinking about which animals alive today are most likely to endure human-caused climate change and mass extinction. (Scientists have identified five major extinction events in natural history, and many say we are living through or on the cusp of a sixth one now, caused largely by human activity.) Others began by imagining the potential environments of the future, and what adaptations might lead creatures to survive in them. A third group thought about the deep history of life on Earth, and what types of animals that used to roam the planet might return, in new forms, long after we are gone.
First off, the survivors: “These are rats, rodents, and also things like cockroaches and pigeons,” said Jingmai O’Connor, a paleontologist at the Field Museum in Chicago. These animals “are doing just fine despite the worst that we’re doing to this planet.”
If these species survive the ecological changes that are occurring now, they might also evolve to fill ecological space left behind by extinct animals. For instance, if tigers go extinct in the next million years, perhaps flightless, carnivorous pigeons and rats will grow to the size of ostriches and snack on the animals that tigers once ate. It’s impossible to predict which specific adaptations might emerge in which animals, but it’s clear that as some species die off, they leave a gap in the food chain that can be filled by other species.
In the far, far future, rodents are especially well poised to thrive if mammal species continue to go extinct. By introducing rats everywhere we’ve settled, humans have increased the genetic diversity of rats, which makes them more adaptable to their surroundings. More genetic diversity means “potential solutions to different [environmental] challenges they might face,” says Alexis Mychajliw, a paleoecologist at Middlebury College. Already, scientists have noted rats evolving adaptations to thrive in specific cities, like New York. They might even be able to further adapt to living amid heavy metal pollution and radioactivity, or to be able to eat toxic waste, Mychajliw says.
And if life on land grows too harsh, rats may be able to slowly adapt to water. Perhaps their evolutionary descendants will lose their fur or sprout flippers, developing streamlined bodies suited for a fully aquatic existence. Other marine mammals, like seals and whales, have followed this path in their transition from land-dwelling creatures to aquatic ones.
Again, these specific evolutionary paths are pure speculation. But experts say they’re within the realm of possibility.
The environments of the future that will shape evolution
The second way to think about animals of the future is by imagining the environments of the future. Environments can drive evolution by exerting selection pressure, favoring some traits over others. For example, some birds have evolved long, pointy beaks to draw nectar out of flowers.
If anything, there will likely be plastic in the environment well into the future. Of all the elements that humans have introduced into the environment, plastic waste is already ubiquitous, and remnants of it might linger for millennia if humans go on producing it as we have. Plastic is “a big source of carbon, which all living things depend on,” said Sahas Barve, an evolutionary ecologist at the Smithsonian National Museum of Natural History. Plastic, he added, could become food, and “any animal that can exploit that will be successful.”
In a way, this development would kind of go full circle: Many plastics are made from petroleum, which is called a fossil fuel precisely because it derives from ancient, transmogrified plant and animal remains. So new life forms could learn to eat the leftovers of really, really old ones.
Termites could be one such critter. These insects already have a gut microbiome — a collection of microorganisms that help with digestion — that breaks down cellulose. Like plastic, cellulose is made of a complex carbon polymer, so it’s not a stretch to imagine termites adapting to break down another polymer like plastic.
“I could easily imagine them evolving a microbiome that helps them then digest plastic,” Barve says. Some fungi and bacteria, including some found in the stomachs of cows, are already able to break down plastic.
The distant future is also likely to be more watery, as sea-level rise decreases the portion of the planet covered by dry land. In envisioning a world of rising seas and altered coastlines, some scientists think about how certain animals might take to living in more marine environments.
Sharlene Santana, a professor of biology at the University of Washington, considers how a bat species might evolve to live off of, and around, the oceans. She imagines a bat with a six-foot wingspan taking shape, capable of gliding like an albatross instead of flapping its wings, perhaps covering hundreds of miles in search of food or islands to roost. It might use finely-tuned echolocation to sense ripples in the water in order to detect fish. (In fact, some bats already do this.)
“This bat is doing something that bats cannot do today, which is to sail and soar on ocean air currents for very long distances,” Santana says. “I call it the sailing bat.”