Fully aquatic whale-rats. Praying mantises the size of dogs. Scientists imagine the future evolution of life on Earth.
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.”
Looking to the past to predict the future
Many of the scientists who spoke to Vox imagined a future environment where humans are no longer around. In doing so, they often drew from animals that existed on Earth before our time — perhaps these types of creatures could make a return down the line.
If humans were to go extinct, our carbon emissions could still remain in the air for a long time, Alter, the Cal State professor of evolutionary biology, said. That could lead to boom times for plants, some of which can thrive in a CO2-dense atmosphere.
The increased density and diversity of plants, in turn, might eventually increase the concentration of oxygen in the atmosphere. Researchers have hypothesized that the growth of insects depends in part on the concentration of oxygen in the atmosphere, which could lead to insects developing larger bodies, Alter says. So a future, oxygen-rich world is one that might be able to foster rabbit-sized praying mantises, or “ants as large as hummingbirds and dragonflies as large as hawks,” Alter said.
It sounds extreme and these visions of the future are merely educated guesses. Then again, something like it has happened before: About 300 million years ago, in the Carboniferous era, the atmosphere was more than 30 percent oxygen, compared with 21 percent today. The fossil record reveals that insects around that time were far larger.
Mairin Balisi, a paleoecologist at the La Brea Tar Pits in Los Angeles, thinks about what type of apex predators might rise to the top of the food chain if humanity does blink out. To that end, she considers what predators existed before humans.
“When we think about large predators in North America alone, we think of the gray wolves, the mountain lion, or the grizzly bear,” Balisi says. But large predators on the continent were much more common up until around 12,000 years ago, during the Pleistocene epoch or most recent Ice Age, with many species of saber-toothed cats and bone-crushing canines roaming the land.
In a future world devoid of human beings, Balisi speculates, such large predators might be able to evolve once again. She is most confident about the saber-toothed cats, whose long, sharp teeth and bulky limbs “evolved independently multiple times in the last 40 million years.” If some lineage of felines persists eons into the future, history could very well repeat itself.
What future do we want?
Modern humans have only been around a few hundred thousand years, but what we do today is likely to have ripple effects for how the natural world looks tomorrow.
The evolution of life depends on the “genetic and development toolkit” as we know it today, says Santana, the biologist at the University of Washington. Because there’s natural variation between animals, some are better at competing for resources and surviving, with the least helpful traits tending to fizzle out, while others crop up with new adaptations. As species continue to go extinct, whether due to habitat loss, agriculture, poaching, or human-caused climate change, many potential sources of diverse life are extinguished from the future, too.
Scientists can still imagine a world where animals that are endangered today carry on and start new branches on the evolutionary tree. The future doesn’t have to belong to just the rats, pigeons, and insects. As long as manatees, polar bears, and monarch butterflies are around, for example, there remains the possibility of their descendants entering the picture sometime in the future.
All of which is worth thinking about if we are to take full responsibility for our role in shaping what the planet will look and feel like long after we’re gone. When we imagine what creatures could come next, we can ask ourselves: What future do we want for the planet? How hard are we willing to work so that future generations of humans are still around to live alongside it?
Giant bugs evolving in the future would be “really, really cool,” Alter said. Especially so, she added, “if humans are actually around to see them.”
In the meantime, while it’s heartening to imagine how different species might bounce back in millions of years, “you don’t want to stop investing in the life that’s around us today,” said Mychajliw, the Middlebury paleoecologist. “There’s a lot we can do right now to ensure that we protect species, protect their genetic diversity, and protect their ability to respond to change.”