Box 2-1: Through a Glass Darwinian
The Carnivorous Hominid: Neanderthal Man
In terms of total calories, the modern American diet, on average, consists of 20 percent to 30 percent meat with the rest of the calories coming from vegetables, fruits, nuts, grains and dairy products. There are also large numbers of Americans with 0 percent meat in their diet. In hunter-gather societies meat comprises about 35 percent of the diet with fruits, vegetables, nuts and honey comprising the remaining 65 percent. For Homo neanderthalensis, the cold-adapted human species that diverged from our ancestors about 600,000 years ago, meat comprised over 90 percent of the diet.At least this was the case for some of the last Neanderthals living in Europe.
Chemical analysis of tiny bits of bone from a skull and a jawbone of two Neanderthals, who lived 28,000 years ago, in what is now Croatia, provided chemical signatures of the foods they had eaten when they were alive. By comparing these chemical signatures with the chemical signatures of the varied animals that lived at the time, the researchers established just what and how much the Neanderthals ate. They were almost exclusively meat eaters. The detailed analysis indicates that their diet closely matched the diets of the most carnivorous animals from that time period. This level of animal protein consumption makes Neanderthals not only the most carnivorous human species to have ever lived but also the most carnivorous higher primate of all time.
According to Erik Trinkhaus a member of the research team. “This research puts an end to the argument about whether the Neanderthals were primarily scavengers. Along with their bones we have found large heavy wooden pointed spears, and stone points that must have been crafted skillfully to make thrusting spears for close-in killing. That kind of hunting prowess obviously required the organization of groups of hunters working together in a sophisticated form of social existence. The Neanderthal people almost certainly ``very good ambush hunters'' who possessed the skills and tools to organize hunting parties large enough to fell huge mammoths as well as wolves, cave bears, horses and deer. “
Interestingly, some of the key selective pressures proposed to explain the rapid evolution of the human brain appear more applicable to the extinct Neanderthals than to our own species. For example, a dietary shift to a much higher percentage of animal foods, with much more concentrated stores of protein and fat supposedly made expansion of the calorie gobbling brain a possibility. Selection for cognitive abilities for planning and coordinating hunts, the so-called man-the-hunter theory of human brain evolution has probably had one of the longest tenures of any of the various brain evolution theories. Adaptation to climatic change has also been proposed as a mechanism facilitating brain evolution. Certainly, the Neanderthal showed the greatest degree of adaptive specialization for cold of any hominid species. They had stout, compact bodies with short forelimbs. They also had unique nasal and sinus structures for dealing with the cold. We could wrap this up by saying that Neanderthals do, indeed, have the highest average brain capacity of any hominid species, so some or all of the above theories are correct.
But wait, there are a few problems here: (1) Neanderthals are extinct. Apparently, this was the result of them coming into contact/competition with our ancestors. (2) When allometric corrections are imposed on the Neanderthal brain it is no longer larger than Homo sapiens sapiens. It other words when the greater mass of the Neanderthal body is taken into account, their brain size is proportionately smaller than that of our species. (3) The real interest behind rapid hominid brain evolution was in explaining the evolution of complex mind/complex behavior.
The development of sophisticated artwork by our ancestors about 40,000 years ago demonstrated a substantial cognitive gulf separating us from the Neanderthals. Symbolic reasoning, creativity and sophisticated cultural transmission are hallmarks of our species. Without these abilities and the complex language skills that augment them, we would not be having this discussion. Clearly, the brain evolution theories described above are made problematic by the discovery of Neanderthals carnivorous diet. However, they should not be totally discounted. Like a lot of other theories that will be discussed in Chapter 3 they may have something valid to say about human brain evolution, at least in the context of certain time intervals.