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> There are tons of things in the human body that are very suboptimal or are purely accidental, from the tons of "junk" DNA, our difficult birthing, the appendicitis, wisdom teeth, the way our knees fold, differences in earwax, etc, etc. Right, but evolution also can explain those; many of these are tradeoffs for things that do deliver benefits. Difficult, premature births are the cost of big brains, for instance. > "Evolution" is just a (fairly tautological when you think about it) observation that "traits that manage to get passed on, subsist". It weeds out very bad traits, but the rest? It's just a giant lottery, not a great design with a teleological goal of "improving". The tautological explanation is extremely powerful, because it means even a small variation that delivers a marginal but consistent advantage is going to be selected for. For instance, a person with dark skin can survive in Northern Europe, and a person with light skin can survive in sub-Saharan Africa, but the ideal skin tones for those regions that optimally trade off vitamin D production with protection against skin damage from the sun are probably pretty close to the ones typical to their indigenous populations. The actual catch is that there’s a lot of path dependence and all changes are stepwise. You can’t just install a new trait or body part that’s been designed from scratch; it has to evolve from an earlier, similar thing. If you look at the bones of your hand, the bones of a bat’s wing, and the bones of the front paw of a dog, the bone structure is basically the same; it’s just by changing the proportions that you can get the structure of a flapping wing, a front foot, or a hand with an opposable thumb. |