When I first started reading about baboons, for some reason I imagined a greater homogeneity among them than among humans. Derpy humans who aren’t very good at getting laid exist, I knew, but somehow I thought derpy baboons who aren’t very good at getting laid would have left the gene pool long ago. I imagined a species of quite optimized individuals. (After all, how hard can it be to be a baboon?)
But there are baboons who drop their babies a lot, baboons who are so nervous about mating they flee when it’s time to act, baboons who panic in the middle of a fight and rather than grabbing the rival’s probable infant to dissuade them from attacking grab a high ranking female adult who then slaps them, baboons who get petulant about being beaten in social interactions and go bounce up and down in branches until they snap, baboons who are big and strong and (repeatedly!) get in the exact right place to win a fight but then panic and vanish, bedraggled baboons, baboons with weird health problems, baboons who can’t figure out social dynamics and keep getting trod on –
there are a lot of weird, incompetent baboons – and this was the most striking thing to me, probably, and the most endearing. These are not optimal animals. It’s wonderful how you think a trait would be so reproductively maladaptive that it would get bred out in a snap, but it seems like you can be an anxious, awkward mess of a baboon and your genes can still keep boxing in the ring or swimming in the pool. The optimal baboons haven’t kept the species ticking along for millions of years – the functional ones have. And it shows.
I suspect this has something to do with the average individual and the average parent being two potentially very different things.
Most living things (at least on the macroscopic scale) die long before they get a chance to reproduce. If you’ve ever watched a documentary about sea turtles, you probably know a lot of them get eaten while trying to crawl from the egg they hatched from to the sea; I wouldn’t be surprised if that’s what the modal sea turtle’s life looks like; it lives for something like three minutes and dies on the beach it hatched on; the ones that even live long enough to feel the ocean on their flippers are a fortunate minority. That sort of pattern holds for any species that’s closer to the r-selected end; the vast majority of individuals never reproduce, the ones that manage to reproduce are a tiny minority, nature’s 1%.
On the other end of the spectrum, humans are possibly the most K-selected animal species on this planet, and until the last century or so even humans had a rate of survival to adulthood hovering somewhere not very far above 50% (though IIRC those figures are mostly for agricultural societies, hunter-gatherers may have done better cause less crowding and less close contact with animals would have meant less transmission of infectious diseases, which were the main cause of death early in life). The most K-selected animal on the planet may have for the vast majority of its existence just barely managed to get above the “odds of living long enough to reproduce are better than a coin flip” line! And then consider people who lived long lives but didn’t reproduce for one reason or another, and a lot of human societies might have been below that 50% mark. Given that, I think it’s safe to presume that in almost all animal species the individuals who manage to reproduce are a lucky minority. That is to say, for almost all animal species, the mean number of offspring is around replacement rate, but the modal number of offspring is zero.
And this is just considering surviving long enough to reproduce, when there are often huge filters after that; for example, in a lot of animal species even within the males that manage to live to reproductive age a hugely disproportionate amount of the reproduction is done by a small minority of highly sexually/reproductively successful males. Probably a lot of species have a lot of variation in reproductive success even within the minority that manages to live to reproductive age.
Even in modern human society, where modern medicine and sanitation has given us a situation where the reproductively successful are a solid majority (what tremendous species privilege we now enjoy!), I wouldn’t be surprised if there’s a significant “the average person doesn’t have average parents” effect similar to the “the average person doesn’t live in an average country” effect. The average parent may be closer to my mother (1 child), but a lot of people may have at least one parent who’s closer to my biological father (who had something like three or five kids with multiple women - the fact I don’t know the actual number offhand says a lot about my relationship to him and his family lol).
And now consider that in a species that reproduces exclusively by sexual reproduction like humans or baboons each individual is the result of a unique or nearly unique (in the case of identical twins) reshuffling of genes; each individual is an experiment. And these genes get reshuffled and interact with each other in complex ways. A tall parent and a short parent won’t necessarily have kids who are roughly half-way between their height; sometimes the kid might get all the short genes of the short parent and all the short genes of the tall parent and end up shorter than either of them. A person with sickle cell anemia is probably descended from two healthy parents who each have mild sickle cell trait.
It’s very plausible that the average individual is less reproductively fit than their parents. Baboons might look more optimized if you look at the average baboon’s parents instead of the average baboon.