[golover721]

> The whole point of evolution is that only genes that promote survival and replication can make it through

While this has been true in our past, we as a species have completely diverged from this. We do everything in our power to save every life no matter what the disorder or weakness. So it is no longer survival of the fittest in the traditional sense.

Whereas in the past someone with schizophrenia or major depression would not likely live a “normal” life and have children, now obviously it is very likely.

[_ywdj]

These genes didn't just appear in the last couple of hundred or even few thousand years.

And the fact that they're widespread means they're selected for, not just not selected out.

[dodobirdlord]

Genetic evidence suggest that the human population was bottlenecked to 3,000–10,000 individuals about 70,000 years ago. Not all that much time has passed since then, evolutionarily speaking, and whatever genetic predispositions were present in that tiny population are probably mostly still kicking around the gene pool. A disorder that doesn't cause problems before sexual maturity or that wouldn't pose an issue for a hunter-gatherer in the environment of evolutionary adaptation isn't really maladaptive, and there's no reason to suspect some number of such traits wouldn't be widespread.

It can also mean that the normal state of the brain exists near a small number of other stable modes, and that a wide variety of small nudges would have similar effects. The article mentions that a study of schizophrenia found that it was characterized in part by extremely rare mutations, suggesting that the brain is at an unstable local maximum, vulnerable to degrading into schizophrenia if unbalanced in any direction. Schizophrenia may in a sense be a much hardier fallback mode of brain operation.

[Broken_Hippo]

That's not really correct, though.

For example, schizophrenia. It doesn't generally show itself until one's early 20's: there are many college students who find their studies halted because of it. It is really easy to have children before this. Depression can render itself after having children, especially in women. We treat it now.

Lots of non-psychiatric disorders are similar: no problems until early-to-mid adulthood. Plenty of time to have children beforehand.

The difference now isn't that genes aren't passed along to children, but more that we try to give folks a more normal life and less misery. And we frown upon the abusive practices that were so commonplace in asylums of yesteryear.

[golover721]

Yes 100% agree. That was what I was saying. Maybe you meant to reply to the parent.