FIRST STEPS

Big brains, opposable thumbs, and tool use made humans masters of the planet, but walking upright came first.

In this fine account, Dartmouth paleoanthropologist DeSilva writes that humans are “the only fully bipedal ape,” and there is no shortage of explanations of how we evolved that way. Darwin speculated that standing freed our hands to make tools, which jump-started the growth of our brains. It’s sound logic, but common sense is no substitute for evidence, and fossils reveal that hominids walked long before they made tools. DeSilva makes a solid scientific case with an expert history of human and ape evolution, emphasizing the importance of food. Humans have a nongrasping big toe in line with the other toes, which are short and bend upward as we walk. This is the opposite of all other primates, whose toes are long and bend downward for grasping. Since Darwin’s time, fossils reveal ancient but upright hominids close to 6 million years old, the accepted period when hominid and ape evolution diverged. Since all living apes walk on their knuckles, researchers yearned to discover the first primate who rose up to become the founding proto-human. It turns out he or she may not have existed. Ardipithecus, perhaps the oldest hominid, walked upright despite possessing feet with some apelike features, and this was also a feature of ape fossils from the period before the common ancestor. As a result, some (but not all) anthropologists believe that knuckle-walking is not a primitive trait; modern apes evolved it. One scientist pointed out, “Asking why humans stood up from all fours is the wrong question….Perhaps we should instead be asking why our ancestors never dropped down on all fours in the first place.” DeSilva devotes the final 100 pages to the generally dismal consequences of bipedalism: dangerous childbirth, backaches, hernias, knee injuries, bunions, etc. On the bright side: Walking is good for us.

Accessible, valuable popular anthropology.