Evolution requires three ingredients: genetic mutations, lots of time, and survival pressures that cause one variant to thrive and the other to die out. While sci-fi visions of the future may imagine humans evolving into beings with telepathy sporting prodigious crania and extra boobs, Michio Kaku says, big evolutionary changes are probably behind us.

It’s because, Kaku asserts, we’ve removed the third ingredient. We control what happens to us in a way that earlier people couldn’t, living in our predator-free homes and enjoying the benefits of advanced medicine. As a result, we’ve lost the kind of death-match evolutionary pressures that used to allow only people with certain traits to succeed enough that they’d have the chance to reproduce. On a survival-of-the-fittest level, life’s just gotten way too safe and it’s just too easy to stay alive.


Kaku’s not saying we’ll stop evolving altogether, of course, but he expects it to be significantly more subtle—genetic mutations will still occur, and hopefully we’ll be around a while. So, no, gills are probably not going to happen unless we genetically manipulate them into existence, something Kaku says is very far off in the future at best.

As the globe warms and seas rise around us, though, I can imagine a scenario in which Kaku would be wrong: If climate change and/or conflicts cause our comfy infrastructures to collapse—as some other sci-fi movies predict—those good old evolutionary pressures may make a comeback yet.