During the past six million years or so several species of humans have simultaneously inhabited Earth at any one time, but today only one species, ours, remains. How did this come to be? This is the question behind part 3 of the NOVA documentary series “Becoming Human” (see my reviews for parts 1 and 2), and the show does not get off to a strong start.
Though I might be a little more merciful on the producers of this documentary than Greg, he was right to point out that the opening segment of the show is worn old tripe about how our species has fulfilled a kind of evolutionary destiny set in place millions of years ago. The entire hominin family tree can be split, the preface suggests, into our proud ancestors and the unimportant evolutionary “dead ends” that lived alongside them. The narrator references discoveries that are “shining light” on the “final stages of our evolution” as if our species is fulfilling some pre-ordained plan that has reached a stop. This is unfortunate, I would have thought better of an award-winning science program like NOVA, but when it comes to human our evolution our own hubris still obscures our view.
Much of the show is based upon the idea that our species caused other species of hominins, such as Homo erectus and the Neanderthals, to become extinct. The idea resembles the “Blitzkrieg hypothesis” for the extinct of large Pleistocene mammals like mammoths; where humans went, large animals and hominins died out. The problem is that this correlation is a bit fuzzy and hard evidence that our species drove other hominins into extinction has yet to be found. For some it may be an appealing idea that underscores our own superiority, but as we all learn in Statistics 101 correlation does not necessary imply causation.
My frustration continued as, after a discussion of Homo heidelbergensis (a hominin in Europe that might be ancestral to Neanderthals if not our own species also), the documentary tripped itself up on the history of science. The show claims that Neanderthal fossils were not interpreted as being relevant to human evolution because evolutionary ideas were anathema until after On the Origin of Species was published in 1859. As ever, the true story is much more complex.
It was not until 1858 that there was a general consensus that humans had existed among the unfamiliar extinct animals of the Pleistocene. (Some naturalists had suggested the idea in prior decades but were not taken seriously.) Therefore any hominin fossil discovered prior to 1858 was simply considered to be a burial that had occurred during historical times. The fact that the fragmentary skeletons of Neanderthals were so similar to ours, and that racist notions allowed some naturalists to say that some members of our species as more ape-like than others, meant that their bones would be interpreted as belonging to either aberrant humans or representatives of “lower” races. The idea that humans existed during prehistory, much less evolved, was a very new idea, and when some of the first Neanderthal bones were found the conceptual framework to understand them was simply not in place.
Nor did the debates cease when the Neanderthals were recognized as a distinct species of human. The question then became whether they were our ancestors or an aberrant “side branch” that were inferior to our Cro Magnon relatives. We now know that they were not the ape-like creatures some anthropologists like Marcellin Boule envisioned but our sister species. They were species of hominin very much like our own. The documentary picks up after mentioning this point, but it was still frustrating to see it fall into the old trap of thinking that On the Origin of Species was immediately and entirely embraced by historical scientists.
The rest of the show attempts pinpoint some reason why our species survived while other hominins, primarily the Neanderthals, perished. Much of this involves trying to find some kind of flaw or weakness in Neanderthals that made them more susceptible to extinction. Our species came out on top so there must have been some reason why we prospered while they perished.
There is also a lot of “just so” storytelling in the show. This is a constant problem in both the science of paleoanthropology and in popularizations of the science, and I can only imagine how some of the conclusions presented in the show is going to change as we learn more. This is not to say that the show is entirely speculative or without scientific merit, but when dealing with our own kind it is difficult to avoid romantic storytelling.
While the show does feature a number of recent discoveries that will be of interest to general viewers in the long run it will be of most value to historians and sociologists interested in how human origins stories have been modified over time. Such efforts to understand the narratives of human evolution is important. I have little doubt that the image of “Homo sapiens the conqueror” will stick with us for years to come, hence making it important that we identify our biases and perspectives when contemplating the evolution of hominins. There is perhaps no other area of historical science that is so vulnerable to the beliefs and expectations of its practitioners, and this is only a true weakness if we ignore this and pretend that we are all objective robots working in a science factory. That, I think, is the main lesson that should be learned from this series. If we are going to examine ourselves in the mirror of history we should be mindful that our ego does not cloud the reflected image.
Part 3 of “Becoming Human” airs tonight, after which the show will be available online.