How much of this change in the last 12,000 years is really genetic, though? Diet and activity are known to affect bone density. That’s one of the reasons white women are more prone to osteoporosis–less physical labor or impact sports. Ice Age foragers lived very different lives than people in agricultural and industrial societies, and bone is plastic.
Were the modern humans in the sample mobile foragers? (If anyone can see the full PNAS article, please check.) If the change is not primarily genetic, can we still say it is evolutionary? Does “evolutionary” cover social evolution?
I wonder how much of a contributing factor “survival” bias might. I sense that unlike dinosaurs, we’re talking about actual bones not fossils (rock that has formed where bones were covered in clay) So bones with lower bone density might not surivive in good enough shape to be successfully dug out of the ground as well.
I’m wondering the same thing. Athletes have thicker bones in those areas that tend to be impacted by their physical activities, e.g. tennis players have thick arm bones. Sadly the abstract doesn’t mention whether they’ve taken this into account and still noted a difference large enough that something else (evolution) was involved.
Our skeletons will be even lighter when we migrate to space. Zero gravity causes bone mass loss, so what will the effect be on children born there? Will they be as fragile as glass? Will they mutate into Guild Steersmen?
Furthermore, I wonder if the less active upper classes might be over-represented in later samples because fancy burials preserve bones and attract archeologists.
And longer lived, and people’s bone densities tend to decrease with age…
Thinner bones, thicker skin. Eventually we should be able to hold our breath and step out the airlock for a few minutes, like mighty space whales.
I note that semi-aquatic and wading behaviors would also have the same effect: heavier bones would be maladaptive, lighter skeletons promoting buoyancy. For waders, lighter legs in particular would be important. Also for our human method of swimming, with the legs behind rather than below us. But which came first, the swim or the skeleton?
Ah. If I understand your statement correctly, you are implying that the lighter bones in modern humans are due to hybridization with space aliens.
Oooo, my second favorite theory – the aquatic ape stage of our evolution. (alien hybridization is sexier)
@funruly told me all the sordid details…
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