Befitting the name of his field, paleoanthropologist Jeremy DeSilva combines a robust study of fossils with a curiosity about the origins of human nature in his book First Steps: How Upright Walking Made Us Human. The result is a thorough account of the evolutionary steps that led our human ancestors to develop bipedalism paired with a compelling origin story of how we developed traits like compassion, cooperation, language and technical ability.
Bipedalism in Nature
First Steps consists of three parts. Part I discusses bipedalism across species, from hominids to apes and other primates, to dinosaurs and birds. I expect most readers will find this section the dryest one of the book. While DeSilva does will to illustrate the fossil record with personal anecdotes and stories of major fossil discoveries, it’s hard to pack millions of years of evolutionary history into eighty pages of text.
Lay readers may get lost in story after story of unearthing partial skeletons from a previously unknown species and what those new fossils signify in the story of bipedalism. And the mixing of scientific genus-species designations with more colloquial names (e.g. interchanging Australopithecus afarensis with Lucy) only makes the history harder to follow. But the human family tree illustration at the front of the book is especially valuable for readers who are less familiar with our evolutionary past.
How Our Human Ancestors Learned to Walk
The fossil record continues into Part II, which addresses the evolution of bipedalism in our human ancestors, and how those ancestors migrated across the earth. As is the case in Part I, DeSilva displays a commendable respect for scientific evidence and processes throughout this exploration. He summarizes a variety of popular hypotheses to explain why humans evolved to walk on two legs and assesses each on the basis of available fossil evidence. But instead of settling on one particular theory, this section instead focuses on establishing when our human ancestors began to walk on two legs and how their skeletons over time changed to facilitate bipedal movement.
The result is perhaps less compelling for readers looking for a definitive Homo sapiens origin story, but this section firmly establishes DeSilva’s scientific bona fides. At the same time, DeSilva indulges his anthropological interests by imagining the lives and deaths of the individuals whose fossils he now studies. In addition to offering fascinating insights into how ancient hominids developed and migrated across the earth, this section best combines DeSilva’s scientific and storytelling prowess.
The Consequences of Bipedalism
Part III extends DeSilva’s examination of the fossil record by detailing the many complications and advantages conferred by moving on two legs. This section delivers on the book’s premise, showing “how upright walking made us human,” and was the section I personally enjoyed most.
Here, DeSilva explores the limitations of a recently evolved bipedal skeleton, from difficulties with childbirth to a propensity for back and knee pain. But he also explains why these limitations allowed humans to develop the capacities that define us as humans: compassion, cooperation and community. It was only through assisted childbirths and a group that watched for predators and other dangers that early hominids were able to overcome the challenges associated with walking on two legs.
In a few especially fascinating chapters, De Silva also explores the many ways in which movement—especially walking—is critical to even modern humans, and offers scientific explanations for problems that arise from a sedentary lifestyle. His explanation of myokines—a class of molecules released by muscular contractions with a variety of health benefits—was new to me, and offered incredible insights about the many advantages conferred by physical activity, from protecting against cancer to improved cognition.
All told, First Steps is an enjoyable scientific account of the history of bipedal motion and the development of quintessential human capacities. While lay readers may struggle with the litany of fossils and species, anyone interested in the origins of humanity will discover many valuable insights in this information-dense yet highly readable book.