Changes in Nutrition May Have Led to Homo Sapiens
Why did Homo Sapiens evolve? That is the unanswerable question of evolutionary biology. There are so many possible explanations for what led to the gradual changes in human ancestral family lines that we have little to no hope of sorting out the possibilities from the probabilities. It is almost as if the hand of Divine Providence guided the subtle changes generation by generation over millions of years to produce modern humans. And that is a dangerous statement to make for in making such a statement one risks losing the respect and credulity of the scientific community while at the same time inviting the pseudo-science of Creationism or Intelligent Design to seize upon the idea and distort it into a mockery of scientific thought.
Our science is certain that some 6 or 7 million years ago one or more groups of apes broke off from the Chimpanzee family and began the long journey toward manifesting as Humanity. They would spin off many sub-groups along the way, perhaps many more than we believe we have identified. But why did one group of apes evolve further and faster than the other, when both groups were themselves the product of a shared evolutionary path that had brought them through tens of millions of years of change to the point of splitting apart?
It is reasoned there was a genetic change at some point, but was the genetic change induced by the environment or was it simply a random event that led to a singular improvement which conferred some sort of hereditary advantage over rival groups? We know through experimentation that genes can indeed be altered during gestation by the introduction or manipulation of changes to the mother. For example, elevating or reducing the levels of certain chemicals in the diet may change the genetic makeup of the offspring. But research also suggests that inheritance of acquired characteristics may occur in multiple species, possibly including hominids.
Hence, there is evidence that changes in environment can lead to inherited genetic traits that may lead to a new species. This data lends itself to the hypothesis that if a group of proto-homo apes were isolated from the mainstream population of Chimpanzees, unable to exchange genetic material with the larger population for an extended period of time (say, 1,000 generations), in an environment suitable for inducing genetic change generation-by-generation the likelihood of a genetic drift occurring relatively quickly would be higher than normal. Once genetic drift has set in any subsequent communication between the two groups would be less likely to lead to genetic exchange.
However, “less likely” does not rule out “possibility” — so there must have been other factors that led to further genetic separation of the populations. It cannot be reasonably assumed that one group of apes spent 1,000,000 years or more completely isolated from the other groups. Culture is another factor that must therefore be considered. Recent research has confirmed that wild Chimpanzees have cultures — that is, their communities develop habits of behavior that are distinctive enough from biologically minimal behavior to be called reasoned or learned behaviors. And even more recent research suggests that culture differs from group to group among Chimpanzees.
These cultural differences have been shown to extend to problem-solving methods used to sample new sources of food. And food sources provide all living creatures with chemical infusions that may alter bodily processes including gestation and embryonic development. Thus it could be that the isolated sub-group of apes not only experienced a different environment from those inhabited by other groups of apes, but that this particular isolated environment introduced new genetic-altering chemicals into the food supply. Once these early human ancestors learned to eat a different kind of food they never turned back to eating or behaving like “mere Chimpanzees” again.
Hence, the appeal of mating with other apes from cultures that avoided preferred foods would have declined significantly. The apes would no longer have been directly competing with each other. In this simplistic model we have no reason for the division of populations into different regions, but nature never leaves a landscape alone. One possible cause for division could have been the formation of a river system that isolated one or more groups of apes and forced them to adapt to new food sources.
The rise of a river system is an appealing hypothesis because if the isolated sub-group of apes gradually adapted to an intake of Omega-3 Fatty Acids in their diet we have reason to believe that neurological development of their embryos may have been enhanced. That is, these apes could have begun producing smarter babies once their diet changed. Dr. Jane Goodall in fact observed meat-eating behavior among wild Chimpanzees. Hence, substituting riverine meats (fish or shellfish) for terrestial meats would provide a rich source of Omega-3 Fatty Acids in the diet that other apes were not necessarily taking advantage of.
Meat comprises a relatively small part of the Chimpanzee diet — substantially less than in most human groups’ diet. Hence, it must also be supposed that at some point the isolated apes increased their intake of meat, capitalizing on the advantages of eating a higher-protein diet. Increased predatory behavior would in fact have been a cultural trait that led to enhanced territorialism. In the past this might have been thought impossible but recent research has shown that Chimpanzees are indeed territorial and capable of waging war.
Hence, our territorial ancestors may have enforced their isolation from other ape groups through increased aggressive behavior and territorialism. Perhaps they even started out as cannibals, attacking and eating other chimp groups, driving away their neighbors (such as during a time of famine). Lacking any normal meat they were used to and driven by desperation, they could have experimented with different types of meat. A change to riverine meat might have had one critical impact on evolutionary development that we are still trying to understand: a prolongation of gestation might have led to greater birth weight which in turn could have led to increases in height.
By growing taller our meat-loving ape ancestors found less and less comfort in the trees and gradually adapted to living on land. The mechanism by which human height developed is still being sought but diet certainly stands out as one of the major factors contributing to that growth. Quite recent research now suggests that Cro-Magnon peoples (Homo Sapiens) were generally taller than Neanderthals, using energy more efficiently.
Longer gestation and increased height may lead to other changes in behavior. For example, large groups of male Chimpanzees are more likely to launch territorial patrols and attack their neighbors than smaller groups. History shows us that large groups of humans are more likely to be aggressive and expansionist as well. There is even evidence of infertile female Chimpanzees joining the males in their patrols and attacks.
As our ancestors grew taller and more intelligent they were able to out-think, out-run, and out-fight any nearby competitors. They gradually seized more and more territory. Chimpanzees who had not evolved with them were left behind both culturally and territorially. These longer gestational periods probably also contributed to greater social organization among our ancestors. Babies required longer periods of protection as they grew taller, and their rates of maturation slowed as their bodies developed toward new intelligence. These rates of maturation ensured that family groups would remain together longer, requiring more cooperation.
Recent computer models suggest that cooperative populations outperform and maybe outlast less cooperative populations. Hence, the biological need to keep family groups together longer for the sake of raising young forced our ancestors to cooperate more than other groups needed to.
These traits and skills thus armed our ancestors for changes in environment and ecosystem that would challenge their survival. They would be better able to survive when climates became drier or wetter, colder or warmer, and thus they would raise more young and increase their populations. Of course, there had to be practical limits to the sizes of those early populations. Dunbar’s Number may not have become a phenomenon for a long time. Our ancestors may have only recently (say within the last 100,000 years or so) become capable of dwelling together in groups of 100-150 individuals for long periods of time.
The tragic discovery of at least four hominins who died together in a cave in Malapa, South Africa about 2 million years ago has led to speculation that a larger group may have been involved in an attempt to rescue one of their members. The story of Australopithecus Sediba may never be fully known but for now they are deemed a relative of our ancestors.
In fact, the many hominid groups that have been documented suggest that the process of separation and evolution repeated itself several times over the past few million years. The three most recently documented contemporary groups are Homo Sapiens (starting Africa and spreading to the rest of the planet), Homo (Sapiens) Neanderthalensis (evolving in the Middle East and Europe), and Denisova hominin. Research has concluded that modern Europeans probably inherited some Neanderthal DNA and that modern Asians probably inherited some Denisovan DNA. So these three groups were able to reunite before two of them vanished.
The European and Asian diets and cultures differ radically from the diets and cultures of southern Africa. One must presume that hundreds of thousands of years ago diets were similarly distinct, and therefore it is reasonable to argue that each regional culture developed in part because of the dietary patterns of those peoples. And within those regional cultures there were probably sub-cultures, either on a semi-tribal or clannish level, varying only slightly from one group to the next.
Because Neanderthals successfully spread across a large swathe of land we know that their family groups increased in number until they had to reach a dividing point, although we don’t know what that division point would be. Speculation suggests that the largest Neanderthal group might have been in the range of 30-40 individuals. Even if they were every bit as aggressive as the modern humans migrating out of Africa 40-60,000 years ago, the Homo Sapiens groups were probably larger in number, capable of traveling across more territory in a shorter period of time, and better able to adapt their diets and cultural habits than the shorter Neanderthals. One might conclude as much about the relatively unknown Denisovans.
Unlikely as it might seem that a Neanderthal male would capture a Homo Sapiens female, it seems credible to guess that Homo Sapiens captured Neanderthal females and kept some as mates. In fact, there is evidence to suggest that the males of more advanced invading populations took females from native populations as farmers spread into Europe. And, of course, we know that often happened as Europeans spread across the Americas and other continents.
Speculative though all this may be, it seems highly probable that the food chain played an important role in shaping both humanity and human culture, and that our ancestors may have been forced to adapt by circumstances beyond their control — or perhaps even as a consequence of their normal territorial aggression. They could have eaten themselves out of a normal food supply or they could have been driven away by a stronger group of apes who expanded their own territory. Either way, it seems highly likely that the discovery and exploitation of a new food source probably began the long, slow process that produced humanity today.
Make of that what you will.