NPR has a “special series” on how evolution gave us the human edge.
Naturally the piece on shoulder anatomy and thrown weapons caught my attention:
Shea explains that the secret of the modern shoulder is its ability to move the arm in almost any direction, even behind the back. That, combined with other early human traits, enabled us to throw with power and accuracy.
“We have a wrist that can move like a whip, that can accelerate through throwing,” he explains. “And your gluteus muscles — you know, your rear end, your thighs, your calves — these are things that make for good running, but they also make for good throwing.”
Early humans first used rocks as weapons to kill prey. As our bodies evolved, we became more able to use advanced weapons like spears and bows and arrows.
It also caught my attention that NPR was presenting the case that a meat-based diet made us smarter:
Our earliest ancestors ate their food raw — fruit, leaves, maybe some nuts. When they ventured down onto land, they added things like underground tubers, roots and berries.
It wasn’t a very high-calorie diet, so to get the energy you needed, you had to eat a lot and have a big gut to digest it all. But having a big gut has its drawbacks.
“You can’t have a large brain and big guts at the same time,” explains Leslie Aiello, an anthropologist and director of the Wenner-Gren Foundation in New York City, which funds research on evolution. Digestion, she says, was the energy-hog of our primate ancestor’s body. The brain was the poor stepsister who got the leftovers.
Until, that is, we discovered meat.
“What we think is that this dietary change around 2.3 million years ago was one of the major significant factors in the evolution of our own species,” Aiello says.
That period is when cut marks on animal bones appeared — not a predator’s tooth marks, but incisions that could have been made only by a sharp tool. That’s one sign of our carnivorous conversion. But Aiello’s favorite clue is somewhat ickier — it’s a tapeworm. “The closest relative of human tapeworms are tapeworms that affect African hyenas and wild dogs,” she says.
So sometime in our evolutionary history, she explains, “we actually shared saliva with wild dogs and hyenas.” That would have happened if, say, we were scavenging on the same carcass that hyenas were.
But dining with dogs was worth it. Meat is packed with lots of calories and fat. Our brain — which uses about 20 times as much energy as the equivalent amount of muscle — piped up and said, “Please, sir, I want some more.”