*A full executive summary of this book is available at newbooksinbrief dot com.
It is a deep part of human nature to want to understand our origins. Indeed, creation stories are ubiquitous among the world’s cultures. Somewhat fittingly, the vast majority of these creation stories have the human race emerging quickly, if not instantaneously—a revolutionary moment befitting a revolutionary species. When it comes to the story from science, on the other hand, while it may be no less spectacular, it is far less abrupt, for it has our species emerging much slower. Indeed, the latest findings indicate that we began branching away from the species to which we are most closely related—the chimpanzee—some 7 million years ago, and that only a series of small modifications spread out over this time has led us to our current state.
However long the process may have taken, though, in the end it was nevertheless revolutionary, for it has changed us from head to toe. Or rather, from toe to head, for the evidence indicates the process began with a modification in our big toe (which made upright walking easier) and ended with self-awareness (which ultimately made us interested in the story of our origin). While the rough edges of this story have been known for decades, recent fossil finds and new techniques in DNA analysis in the past 5 years have allowed the story to come into much clearer focus. Armed with these new discoveries, science writer Chip Walter takes on the story of human origins and evolution in his new book 'Last Ape Standing: The Seven-Million-Year Story of How and Why We Survived'.
The story begins with our ancestors living in the rainforests of Africa several million years ago (much like our closest living relatives, the chimpanzees, continue to do to this day). At the time, a changing climate was beginning to threaten these rainforests, and causing them to recede. As the rainforests receded, our ancestors living at the outer edges were increasingly pushed out onto the savannah—a new and hostile environment to which they were not well adapted. Adapt or die was the reality of the day, and fortunately, our ancestors began to do so. (Actually the line between our ancestors and ourselves is not so direct: as the author points out, it is now thought that at least 26 other proto-human species arose, but that we are the only one that remains).
First things first, it is now thought that a mutation emerged that allowed our big toe to support more of our body weight, and this made it easier for our ancestors to walk upright—which held many advantages, including efficiency in locomotion, and enhanced sight lines. From here, other mutations followed that further facilitated our ability to walk bipedally—including a complete pelvic restructuring.
At the same time as our bodies were being restructured for the purpose of walking upright, our brains were also beginning to grow. This was highly adaptive, it is thought, for it allowed our ancestors to better cooperate for the purposes of securing new sources of food, as well as fending off new predators. It was the increased sources of protein out on the savannah (and the energy that it provided) that allowed our brains to evolve larger in the first place, and once our brains began to evolve larger it allowed for increased cooperation and even more sources of protein—thus putting into effect a positive feedback loop that was leading to very large brains indeed.
Unfortunately, our two latest adaptations were coming into conflict, as bigger brains became harder and harder to birth out of narrowing hips (which were choiceworthy for upright walking). Rather than compromise, though, evolution had another trick up its sleeve: it simultaneously delayed our development, and also started forcing us out of the womb sooner, before our brains had grown so large that they weren’t able to fit. The solution was ingenious but extremely dangerous, for it left us far more helpless for far longer after birth, which made us that much more susceptible to being taken down by predators. Nevertheless, the slowed development also had its advantages, for it afforded us a much wider window within which to learn about our environment, which helped us adapt to and overcome it.
In the final piece of the puzzle, the ability to think symbolically arose, and this ability not only contributed to our being able to communicate with sophisticated language, but also with our being able to represent ourselves symbolically, which ultimately allowed for self-awareness. Both of these allowed for the rise and flourishing of culture, which represents our greatest advantage as a species.
Walter’s book reads very well and his explanations are very easy to follow. Although the outline of the story that Walter tells is by now familiar, the author does a very good job of covering the latest findings and theories that are emerging that are allowing us to gain a fuller picture of just what happened (especially when it comes to hominid sub-species evolution, and the role of neoteny in our evolution).
I felt there were just two main weaknesses in the work. First, Walter does not address the change in mating and childcare patterns (towards more monogamy and paternal involvement) that made delayed development possible. And second, Walter’s discussion of the future of human evolution (both natural, and man-made) is scant and somewhat wanting. Other than that, though, the book is a valuable addition to the evolving story of our evolution as a species. A full executive summary of the book is available at newbooksinbrief dot com; A podcast discussion of the book will be available soon.