Imagine for a moment if we all still walked on our knuckles.
It would be a very different world, no?
Of course the world looks the way it does today because we are upright.
(We = us humans.)
By going bipedal, our brains grew much larger. That change led to agriculture, the Renaissance, pepperoni pizza, the Super Bowl, reggae music, and trips to the moon.
When we study anatomy—when we build anatomy using the Anatomy in Clay® Learning System—this fact is easy to overlook and/or forget.
We were once quadrupeds. That’s why the backs of our hands (the knuckle side) is the dorsal side.
The evidence of our shift from quadrupeds to bipeds is everywhere.
The human foot has changed from grasping structure to load-bearing platform. There’s an arch, too, to improve energy transfer from heel to toes as we walk. Human forelimbs are smaller today because they concentrate on carrying, holding, and manipulating objects with precision.
As a result, our forelimbs provide decreased strength relative to body size (compared to apes). We can stand on our hindlegs (well, legs) for long periods of time; apes get tired because their femurs have not adapted. Our gluteus maximus helps prevent our upper trunk from pitching forward when we run.
On and on. Hips, pelvis, vertebral column, skull, and the brain. There is evidence everywhere you look. Brain size began to increase 2.4 million years ago, but modern levels of brain size were not reached until about 500,000 years ago. The human brain is three to four times larger than its closest relative, the chimpanzee.
Yet the human anatomical structure is not perfect.
We’re still paying the price for going upright. Knee pain. Back pain. Arthritis (which has turned up in prehistoric hunter-gatherers). For women, the narrower hips of moving upright led to a smaller birth canal (just when babies heads were growing larger).
Of course many puzzles remain in the history of human evolution. As we always like to mention, thank you to the hard-working scientists who are working every day to answer these questions. We remain firmly convinced that the full story will eventually be told.
We have been gone from “marginal creatures” of 150,000 years ago (that is Yuval Noah Harari’s term in Sapiens: A Brief History of Humanklind) despite understanding the benefits of fire. We humans then were “minding our own business” (Harari) among the other animals and wildlife. Something changed. Communication played a role. Food sources played a role. Migration, etcetera.
“What was Sapiens’ secret to success?” asks Harari. “How did we manage to settle so rapidly in so many distant and ecologically different habitats? How did we push all other human species into oblivion? Why couldn’t even the strong, brainy Neanderthals survive our onslaught?”
Great questions. We’re still working (well, top-notch scientists are still working) on all the pieces of the full story. Answers to come. We have no doubt.
But at least we have the evidence of the transition from our time as quadrupeds. We carry it around with us every day.