For example our hands become wrinkly after getting wet so our ancestors could grip onto trees better after swimming.
Would we really go extinct as a species if we didn’t develop that extremely specific trait at one point?
Same for crying as an emotional response, or eyebrows keeping sweat out of our eyes, or goosebumps making our hair stand to be more intimidating to predators.
I understand why these would be helpful, but I don’t see why these were so necessary to the human race’s continuation that nearly every human has these traits.
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Helpful for survival is occasionally necessary for survival. Humans could all be myopic and we’d mostly survive, but some people *would* die because of it.
It doesn’t have to mean life or death for everybody, just for enough people over millions of years.
Evolution isn’t trying to creat the perfect version of a species. Evolution is a good enough game, if something is good enough to reproduce it’ll make it
Things like these were neither helpful no harmful but the “people” who had these features were the ones that had other things that made them more favorable for reproduction so they simply didn’t evolve away.
Evolution is not a sentient being choosing the better traits for the species. The people who cried after a sad event managed to pass their genes to the next generation and the ones who didn’t were not able to do so, and that’s why we do it today.
If a trait exists in almost the entire population then it can be assumed that those that didn’t develop it died off before successfully breeding. The trait might not be useful anymore but it most certainly was at some point as evidenced by the lack of anyone without it.
“helpful for survival” often means breeding earlier, breeding more often, breeding for longer, having healthier children, being able to raise more children without overextending yourself, being able to help your children raise their children because you live longer etc. An advantage over other members of your species means that your genes will be more prevalent in the population.
Evolutionary pressure can work even under very subtle evolutionary pressures. If a simple change means a population with an adaptation is 1% more likely to survive, over generations that builds, 1% improvement in fitness still means after 100 generations there will be 2.7 times more individuals with that adaptation than not. Over 500 generations, 144x more individuals.
This is just the power of exponential growth.
It’s not that a trait has to be a life-or-death decision (though obviously, in evolution, nothing is “deciding”). The trait just has to make it so that you leave behind more descendants than individuals that don’t have that trait.
An example of this is the fact that humans can’t make our own Vitamin C.
Vitamin C is an essential nutrient. Most mammals can make it themselves. We can’t – if we don’t have it in our diets, then we develop scurvy. So why can’t we make our own?
Well, millions of years ago our ancestors had a diet that was naturally rich in Vitamin C. By a freak mutation, one of our ancestors lost the ability to make their own Vitamin C. If we hadn’t had our diet, this would have been fatal, and they would have died and not passed it on.
But that’s not what happened. Since they were already getting Vitamin C through their diet, the loss of that functionality didn’t kill them. Instead, they were able to use the energy and resources that would have been spent synthesizing Vitamin C to do other things. Develop a bigger brain, make more of a different vitamin, whatever. The point is that thanks to that mutation, they had an advantage over other human ancestors. Their descendants retained that advantage, and eventually the trait spread to our entire species.
>Would we really go extinct as a species if we didn’t develop that extremely specific trait at one point?
No, it’s more subtle than that. All it takes for a “very mildly advantageous” gene to spread is that it doesn’t cost much, and that it saves the lives of a few people. What you’re missing is the insane *scale* of it. Sure, saving 1 person out of 100 000 in some extreme scenario doesn’t sound like much… But consider if the population is 100 million and we’re looking at 1000 people where this gene meant life or death. And then you let time do its thing over maybe a few hundred thousand years where this extremely unlikely situation keeps repeating. Suddenly it doesn’t seem so far fetched that the genes start drifting after a while.
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