Sort of along the lines of sleeping as a group, I theorize that some of the (modern) human datapoints are due to the gradual isolation of humanity combined with the sleeplessness that comes with the first few years of child rearing.

Historically, child rearing was supported by a tribe of people. Nowadays, we have isolated ourselves to the point of one or two parents and maybe a grandparent or two. Babies can take years to get to consistently sleep through the night. So we have taught ourselves to be more “self sufficient” and just deal with it.

Or maybe I just think this because my 6 month old woke up four times last night and I’m losing my mind.