Thankful Day #22: I am thankful for bipedalism. Walking upright freed up our hands, allowing our ancestors to start making tools like this Olduvai chopping stone 1.8-2 million years ago. Walking upright came with a trade-off, though--the pelvis evolved with a smaller outlet, necessitating earlier birth and a longer period of dependence on parents. Given the prevalence of 30-year-olds living with their parents, the process evidently marches on (so to speak).
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