Human fetuses evolved to slow shoulder growth for easier delivery. CT scans of humans, chimpanzees and macaques reveal that human collarbones slow their growth rate in the final months of pregnancy, perhaps to make it easier for babies to squeeze through the pelvis.

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The ones with high growth rate of shoulders just died inside, probably even taking their mothers with them.


Some fetuses need their collar bones broken for a successful delivery. I imagine this wasn’t standard procedure in caveman times so broad shouldered babies and their mothers may have reduced themselves in the gene pool.


I mean, it’s still not that easy to squeeze through. Get your head in the game, evolution.


I hate when “intent” is given to natural processes, especially evolution.


It’s not that they do it for a reason – they just do it – the reason is the idea overlaid onto this reality.