HOUSE CATS WILL RULE THE WORLD

Domestic cats may evolve into the alpha predators of the future.

Cats have had a remarkable run the past few thousand years. Starting as minor players in African ecosystems, they quickly evolved and took over the planet by wrapping the human species around their little toes. Today, there are nearly 1 billion domestic cats found throughout the world.

What does the future hold for our beloved feline friends? New breeds will continue to be developed, some becoming even better domestic companions adapted to modern living, others bred to exhibit unusual traits (like the sphynx, lykoi, and munchkin). But the real action is going to be out in the wild. Large populations of feral cats are now established on every continent but Antarctica. Those cats are going to start evolving. They probably already are.

There are three important ways in which evolution occurs. First, when a species encounters new environmental circumstances, natural selection can push it to evolve, and to do so very quickly. Darwin was right about so many ideas, but he got this one wrong: He thought evolution happened only at a glacial pace, but we now know that rapid evolutionary change is common when selection is strong.

The several hundred million feral cats roaming the planet are probably already adapting to the unique circumstances they’re experiencing in different regions. Consider the vast array of different habitat types occupied by feral cats in Australia: scorching red deserts, cold and snowy temperate mountains, rainforests and grasslands. Desert cats are probably evolving ways to cope with heat and scarce water, mountain-dwelling populations in the south to the cold and snow. Different prey species that occur in different places require different hunting adaptations. Different predators—dingoes, Tasmanian devils, big lizards—require different ways to escape. Walking on sand poses different challenges than climbing on boulder fields.

A quick survey of the variety of small cat species around the world illustrates how feline species have adapted to different environments: margays with reversible ankle joints to descend trees headfirst, sand cats with the soles of their feet covered in hair to walk across deserts, fishing cats with webbed toes for the life aquatic, just to name a few. Domestic cat populations could well evolve in similar ways.

Second, isolated populations tend to evolve in different ways. For this reason, islands are famous as “theaters of evolution.” Just as the famous land tortoises of the Galápagos are different from one island to the next, the feral cats of Fiji are likely to diverge from those on Tahiti, even if the environments are very similar. And with cats established on hundreds, if not thousands, of isolated islands around the world, it’s only a matter of time before they evolve into different species.

Finally, nothing drives evolution more than opportunity. And perversely, nothing provides evolutionary opportunity more than widespread extinction. Mass extinctions are bad news for the many species that perish, but for the survivors, they’re a golden ticket for evolutionary success. In the past, when ecosystems recovered from asteroid impacts, volcanic eruptions, or whatever catastrophe caused species to die off, new species arose to exploit the newly available resources. For example, the asteroid that killed off the dinosaurs opened the door for mammals to diversify extensively, producing species like elephants, whales, bats, cats—and us.

Sadly, the world is in the midst of another mass extinction event. According to one U.N. study, 1 million species could disappear in the near future. Eventually, however, humanity will have to get its act together and stop pillaging the environment in order to survive. Unless we completely annihilate all life, ecosystems will eventually recover as they have in the past. Evolution will produce new species. Global species richness will rebound. This newly reconstituted biodiversity will be descended from the species that have survived our onslaught.

Over the past 10,000 years, humans have wiped out many of the world’s largest predators. North America has lost giant short-faced bears, dire wolves, American lions, American cheetahs, jaguars, and two species of saber-toothed cats. The mainland of Australia has lost all of its large mammalian predators. Today many predator species all over the world are highly endangered, such as tigers, polar bears, and African wild dogs (also known as painted dogs). The loss of many of these species will be tragic, but when the larger predators cease to exist, the door will be wide open for cats to fill the void.

Once (no-longer-domestic) cats are alpha predators, how will they evolve? Some new cat species will become much larger. Domestic cats are on the small end of the feline size spectrum. Larger predators can kill larger prey; with most larger predators gone, domestic cats will seize the opportunity to get bigger. And if history is any indication, they may get a lot bigger—the largest feline ever was the South American saber-toothed cat, Smilodon populator, which weighed nearly half a ton!

Speaking of sabercats, it seems likely that the domestic cat lineage might produce one of them as well. Saber teeth evolved multiple times in cats and their relatives (and also once in South American marsupials). For much of cat history, saber-toothed species were more common than their less toothy relatives. The last sabercats were around until about 10,000 years ago in the area now known as Los Angeles; perhaps someday a sabertoothed domestic cat descendant will be taking down buffalo on the Western Plains.

Some cats like water—could there be an otter-cat in the future? Weasels are long, slender and short-legged to dive into burrows—why couldn’t a cat do the same? The munchkin breed—the corgi of cats—is proof that short-legged cats can exist. Perhaps a cat will evolve that lives entirely in trees; if such an arboreal feline species arose, maybe it would then evolve flaps of skin to become a glider, sailing from one tree to another like the giant flying squirrel of Asia (which is the size of a small cat).

The biggest question of all is this: Would all descendants of the domestic cat still look like cats? All cat species today, and all that have existed in the past, share the same essential cat-ness. Even the most distinctive contemporary cat, the cheetah, is clearly a cat. This homogeneity suggests that felines have found a winning evolutionary formula and may well stick with it. But history isn’t destiny—maybe the domestic cat lineage will strike out in new directions and produce species unlike any previous feline. Consider that whales evolved from hoofed mammals, seals from terrestrial predators and bats from … well, we still really don’t know where bats came from.

The first known cat species, Proailurus, lived 30 million years ago and gave rise to lions, cheetahs, saber-toothed cats, and more. Will Felis catus, the domestic cat, spawn an equally rich evolutionary lineage? I wouldn’t bet against it.