With all the possible mutations out there, life could look a whole lot different in a hundred thousand years. But, what if humanity’s evolution were to happen on a much faster timetable?

That's exactly what's going on, argues Juan Enriquez, author of Evolving Ourselves: How Unnatural Selection and Nonrandom Mutation are Changing Life on Earth.

While random genetic mutations do in fact take a long time to impact the direction of a species, Enriquez points out that genes are “turned on or off” based on environmental factors, and things can change quickly from generation to generation. He brings up the unsettling example of the Dutch during World War II:

“When the Nazis were losing, they decided to starve the Dutch. And the mothers who had babies during this period, had babies that had lower birth weight, had less vitamins, etc. But the strange thing was, that persisted across generations. So once those genetic switches are flipped… you may not be modifying the core genetic code, but you’re modifying the instructions as to how that code is executed.”

Similar evidence can also be found among survivors of the Cambodian Genocide and an 1836 famine. But it’s not just famine that can shape us.

Consider a fox domestication study that Dmitriy Belyaev conducted in Stalin’s Russia. Belyaev only allowed the most docile in each generation of foxes to breed, and in a relatively short time, the foxes behaved like puppies. They were eager for human contact, whimpered when they were ignored, and licked humans. The foxes’ bodies even changed, gaining floppy ears and short tails.

Enriquez thinks something similar could happen to humans as more and more of us move to cities. (Though, most likely, minus the floppy ears.)

“As you take big chunks of humanity and you say, you’re going to live in smaller apartments, you’re not going to have space to roam, if you’re violent, there’s going to be eight people on your floor that are mad at you… We watch the evening news and we think, we’re as violent as ever. That’s just not true.”

Enriquez believes that we’re also going to change our bodies to adapt to space travel. Because humanity must colonize space in order to survive (in the opinion of Stephen Hawking, at least), Enriquez envisions us adapting our physical forms to meet the myriad challenges of space, including gravity, childbirth, and radiation. (These issues, unsurprisingly, have been explored in numerous science-fiction novels)

These changes to our species might seem scary and unsettling to some, but Enriquez says they may offer the key to massive life extension. And he sees hope in “unnatural selection.”

“We tend to associate the word unnatural with bad and evil and horrible. But unnatural selection has been incredibly beneficial, at least to our species. We’re living longer, there are more of us, we’re living better than at any point in history. I think we’d rather be born into this period of history than any other. Wresting that [control over our evolution] from nature, I think, is not a bad thing.”