First Steps

February 15, 2021
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.

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Starred review from April 1, 2021

Why, how, and when did human ancestors first walk on two feet? Why are humans so uniquely bipedal, at least among mammals? DeSilva (anthropology, Dartmouth Coll.; A Most Interesting Problem) tackles these issues in his latest work. Its scope includes the several-million-year prehistory of bipedal hominins. DeSilva has a gift for identifying important but often overlooked observations regarding bipedalism; for instance, he notes that humans are quite clumsy compared to four-legged mammals. He also discusses anatomical differences between human bipedalism and bird bipedalism. Readers will glean a solid framework of human origins, including the divergence of chimpanzee and hominin ancestors some six million years ago. He discusses various theories attempting to explain human bipedalism, such as the aquatic ape hypothesis. Other ideas, such as the ability to carry food with freed arms, offer plausible scenarios favoring bipedalism. While the subject of human evolution might seem daunting--especially discussions of the relationships between ape and hominin ancestors--DeSilva uses personable language and always keeps it interesting. VERDICT DeSilva provides a scholarly yet accessible conversation on the origins of human bipedalism. A great introduction to human origins, anthropology, and primatology for general audiences. Includes recent discoveries that are updates to previous popular works.--Jeffrey Meyer, Iowa Wesleyan Univ.

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