Rosio Pavoris

Here’s another argument I’ve seen come up a few times—I don’t intend to correct every single misconception I run into on the intertron, but this one is basic and common enough it’s worth addressing.

Have humans stopped evolving?

The argument tends to go something like “normally the weak die out and the strong survive, and that’s evolution, but humans have the technology to let the weak survive so clearly we aren’t evolving anymore!”, though usually the spelling is worse than that.
This reflects some fundamental misunderstanding of evolution, and natural selection’s place in it.

Selection and Evolution

Selection (be it natural or artificial) isn’t what makes species evolve. You could say that it guides evolution, but it doesn’t drive it.
The distinction is rather important if you don’t want to make an ass out of yourself by asking stupid questions.

The real driving force—the only driving force¹—of evolution is mutation.
This is obvious if you think about it. Selection (of any kind) doesn’t produce variety, and Lamarck, obviously, was wrong.

What selection does is prune out the harmful mutations (because yes, most mutations that have phenotypic effects are harmful), and get rid of the “less fit” organisms.
“Less fit” for what? To survive and successfully breed in their habitat.

This means that if the habitat of an organism hasn’t changed in a long time, it’s likely to be relatively close to ideally suited to thriving in it, which means that the overall effect of natural selection will be to maintain the traits of the parents in the offspring.
To most people who ask this sort of question, natural selection would seem to be the opposite² of evolution in these cases.^{3 4}

If the environment the organism has to survive in has changed recently, a species can undergo very dramatic changes in relatively short periods of time, but it’s important to realise natural selection is not the driving force here—mutation is.

Selection can only act a brake on evolution. If technology enabled mankind to be free of any of the pressures of selection, we’d be evolving faster than ever.⁵

Selective Pressures on Humanity

That was the first thing I wanted to get out of the way. Next, the claim that technology enables mankind to be free of any of the pressures of selection.

It’s bullshit.

Have we cured all diseases? Malaria alone still kills between one and three million people a year, and that one we supposedly know how to cure. Even the goddamn measels claim hundreds of thousands of people each year.
And forget diseases—what about our own bodies? Cardiovascular disease is still the most common cause of death worldwide, and cancer is responsible for 13% of all deaths.
And don’t forget that most pregnancies end in miscarriage; that’s some powerful selection right there.

And technology has brought us another very potent source of natural selection: pollution.
Air pollution means that suddenly a mild asthma that wouldn’t necessarily kill you in the past becomes life-threatening. Water pollution kills over five million people a year. Soil pollution degrades the quality of our food and threatens our health. Radioactive pollution renders us sterile. Noise and light pollution increase stress levels, which leads to increased blood pressure and heart problems.

And what about sexual selection? Or will you just have kids with anyone?

Conclusion

To sum up, yes, humans are still evolving, and yes, we’re still under selective pressures.
We’ll be subject to natural selection for a long, long time, and there’s no reason to believe we won’t be subject to artificial selection for a long time after that. And even if we weren’t, we’d still evolve. I’m sure technology affects natural selection (and by extension evolution), but it doesn’t stop it.

Obviously asking questions is always a good thing, but if you’re going to base your assumptions regarding evolution on Pokémon, it might be a good idea to just pick up a book in the future.
There are plenty of good, readable books out there that will help you think about evolution. Personally, I’d recommend Richard Dawkins’ The Selfish Gene (obviously), and Daniel Dennett’s Darwin’s Dangerous Idea.

¹ Yes, sexual recombination helps, but if you only had sexual recombination as a source of variety, your total population would shrink rather exponentially; and even sexual recombination requires variety to start with, and the only source of that is random mutations.

² “Devolution” isn’t a term that makes sense, shut the fuck up. The opposite of evolution is a lack of evolution, not devolution.

³ Obviously this is related to Eldredge and Gould’s punctuated equilibrium, which predicts rather long periods with no real change interspersed with quick periods of rapid change (arms races aside), and should be distinguished from saltationism or quantum evolution. The idea of gradualism isn’t bullshit as such, it’s just a lot rarer.

⁴ Yes, I’m essentially an adaptationist. No, that doesn’t mean I don’t think neutral phenotypic effects (like the African rhinoceros’ second horn) can’t be fixed, à la spandrels. Grow up.

⁵ I like footnotes.