In the search for a common ancestor, Peter Andrews points out in An Ape’s View of Human Evolution, we should not expect a hominid that resembles living great apes or
The surviving “great apes” consist of humans, orangutans, gorillas, and the two species of chimpanzees and bonobos that are our closest relatives. Collectively they and their extinct ancestors are known as hominids. (Gibbons are also apes, but are classified separately as “lesser apes.”) Human ancestors subsequent to the human-chimpanzee divergence are known more specifically as hominins. Thus, that enigmatic and elusive most recent common ancestor represents the parent stock to both humans and chimps. The search for this forebear is complicated by the scarcity of hominid fossils. The once famous claim that all hominid fossils could be displayed on a billiard table is both wildly exaggerated and certainly obsolete, as thousands of such fossils have been recovered in recent decades. Still, these remain no less rare, and much of what we do have is fragmentary. I have always especially been struck by the paucity of hominin fossils, but it turns out that this represents a veritable abundance next to the scant traces of fossil apes that have come down to us. Andrews wonders aloud about the rich array and potential numbers of extinct apes that might have once walked the earth, while he painstakingly takes the reader through a carefully detailed examination of the fossil evidence in hand, much of it from the Miocene Epoch (roughly 23 to 5 MYA).
I am grateful to the Cambridge University Press for providing me with a copy of this book for review, but I might not have requested it had I known that it was such a highly specialized work. I have followed studies in human evolution for many years, but my training is in history not paleontology, so I found portions of the book a challenging read, especially the many chapters given to descriptive fossil morphology, pregnant with anatomical detail. An Ape’s View of Human Evolution is clearly not intended for a general audience, although the reader with a strong background in evolutionary studies can well appreciate the first six chapters as Andrews reviews what is known about fossil apes in general, and artfully reconstructs the respective environments that hosted them. His discussion of the isotopic signatures that reveal the kinds of food that nourished them – C4 plants vs. C3 grasses – is a reminder of the wealth of detail today’s science can bring to bear in evaluating fossil evidence. And this is, of course, a field open to constant revision: Andrews notes that the once popular view that knuckle-walking, the unique form of locomotion seen in chimps and gorillas, might be a kind of forerunner to bipedalism and therefore present in a common ancestor, has largely been refuted by studies that seem to indicate that knuckle-walking developed similarly but independently in each of these great apes and is therefore not a key to their common evolution. In fact, it turns out that knuckle-walking does not even establish a sister relationship between chimpanzees and gorillas; like wings that developed independently in birds and bats, this unusual type of locomotion is analogous rather than homologous. [p25-26]
This is great stuff! Unfortunately, the narrative thread abruptly breaks off as subsequent chapters are devoted almost exclusively to fossil ape morphology, which felt more like the kind of material suitable to an appendix. In a similar vein, I was reminded of the middle portion of David Anthony’s otherwise magnificent The Horse, the Wheel and Language, when it appears as if Anthony has incongruously inserted a sizeable chunk of his archaeological dig notes smack dab into the center of the chronicle. Fortunately, Anthony later resumes the narrative. This cannot be said of Andrews, who only very briefly revisits earlier themes in his final section, which merely consists of some twenty pages of text. It is clear that the morphological material that makes up roughly half of this volume is intended to buttress reasoned arguments for what we can expect to find in a common ancestor, but a stronger concluding chapter that connected all of the dots with greater clarity would have been most welcome. Still, as noted earlier, this book is intended for a specialized audience and the abundance of material included by Andrews in this scholarly work is no doubt a welcome addition to the literature in this exciting field as we continue to seek and evaluate critical evidence to chart the course of human evolution.