My last post reviewed Donald M. Morrison’s book The Coevolution of Language, Teaching, and Civil Discourse among Humans. This entry is a brief meditation inspired by my reading.
The fossil skulls of our Homo ancestors show an amazingly rapid growth of the Homo brain. Homo habilis (2.8 million years ago) had a brain only slightly larger than that of a chimpanzee. By 200 thousand years ago, the brain had tripled in size. 2.6 million years is long by most standards but is very fast for an organ to triple in size, and is especially impressive when you realize that sustaining neurons requires much greater support in calories than say muscle. The growth of the brain indicates a steady improvement in diet during those same 2.6 million years. How does that kind of steady growth persist for millions of years?
Morrison argues, reasonably enough, that the pressure to evolve so steadily over a prolonged time is usually an arms race and as predators gain speed so prey species improve their speed too and the circle continues. Predators kill and eat the slower prey, so the faster prey is selected. The slow predators starve while the faster predators survive to have descendants. The enlarged brain permits the Homo genus to remember more, develop language, technology, and culture to a much higher level than our chimpanzees. Morrison's Chapter 4, “An Evolutionary Explosion,” does a fine job of considering the suite of changes made to the body of our ancestors to produce us, not just our brain size but our bipedal, gracile shape and reworked hands. (Some how he omits the loss of body hair that must have produced a serious crisis in a species that uses mutual grooming as a major means for social bonding.)
Morrison points out that there is a kind of trap in arms-race evolution. As you develop brains that require a changed diet, there can be no going back to the original diet. If the new foods become scarce, other high-power foods are required. If finding the food requires some improbable solution that calls for more than instinct, the species must be able to teach its children how the solution works. There is a cycle of dependency. Smart solutions demand that the solutions be passed on through the generations. They must be taught. “Without language, it would not have been possible to engage in the kinds of cooperative, joint attentional activities that allowed hominin ancestors to afford their enlarging brains, thrive in the ancestral environment, spread across the face of the Earth, and fly to the moon.” (p. 79) Thus, language has to have already existed in some form while the brain was enlarging. It cannot be just the cherry on top of a long growing brain.
Missing in this discussion is a consideration of who we were racing against. It takes two to tango through an arms race. And there is a peculiar thing about evolutionary arms races; the species do not benefit so much from the process. The predators are faster, but the prey is faster too. That’s why prey are only a little bit faster than their predators. When naturalists encounter something like the pronghorn antelope of the American prairie which is far faster than any of its predators, they know to check the fossil history. The plains used to include cheetahs which could give the pronghorns a run for their money. The cheetahs are gone and inevitably the pronghorns will eventually slow down.
But who were our ancestors competing against to get so smart? Homo habilis was already slightly larger brained than chimpanzees so they did not have to get much smarter to have a decisive intellectual advantage over their cousins. There is no point in getting much larger brains, and there may have been disadvantages. Smart as we are, we are physically much weaker than a chimpanzee. Chimps can tear us limb from limb and rip off our faces. You do not want to engage a chimp in a round of fisticuffs. Yet we got weaker and weaker and smarter and smarter.
So let’s take a hint from the speedy pronghorns and look to the fossils. There the evidence shows something remarkable. At first, varieties of the Homo genus began to multiply. Not that long ago, there were Neanderthals, Denisovans, and our own line thriving at the same time. The others died out leaving only us. Somehow we have outlasted them all. It suggests that populations of Homo rather than individuals were doing the competing. Neanderthals were apparently doing fine until our line joined them in Europe. Then, over many generations, the Neanderthal population dwindled to nothing. A similar story can be told about the Denisovans of central Asia.
Morrison says at one point, “Groups with larger numbers of innovators outcompeted other groups,” (111) putting the competition at the group level. But he also says, “in a snowballing effect, more complex technologies would have selected for individuals with the cognitive capacity to use them,” (112) putting the competition back on the individual level. I am very disappointed in this ambiguity because I thought I had found some company. Talk of an arms race that left us so much smarter than our nearest living primates, implies a race with competitors who are no longer around. The likeliest groups are other populations of big-brained proto-humans, so that’s likely to be who we were racing against. Then, Morrison puts such an emphasis on the group benefits of language, especially teaching, that at first I assumed he was talking about group (or to put it technically: multi-level) competition. After all, that is how human history works today.
During the past 300 years many human populations have shrunk profoundly or died out altogether in the competition with expansive, imperial peoples. The Comanches, for example, did not meet their fate because individually they were not as tough as the newcomers. Quite the opposite; in one-to-one duels with the white newcomers, the Comanches almost always won. Yet within a human lifetime they were almost completely eradicated because they as a group could not match the technological and organizational strengths of their group-conscious enemies.[1] Just as we can ask when humans began to use language, we can wonder when their evolutionary story became more dependent on multi-level selection than on the selfish gene. I lean toward the proposition that language and group-competition are about equally old, and I am sorry Morrison does not tell us where and why he stands on the issue.
Instead he wants it both ways, “As the use of language became essential to both individual and group survival, individuals born with genetic programs that made them, in one way or another, slightly better at using language (e.g., slightly better short-term memory, slightly better at taking another person’s perspective) became slightly more likely to survive into adulthood, find suitable mates, and raise offspring to adulthood.” (113) I have never found a convincing argument that selection would actually favor the better speaker. I’d like to think that brains beat brawn and the pen is mightier than the sword, but I doubt the victory when we are speaking on a one-vs-one level. To counter this doubt, Morrison puts forward a remark by the psychologist Geoffrey Miller, “Language puts minds on display where sexual choice could see them clearly for the first time in evolutionary history.” (169) It is a fair point, one to think about, but, especially in the age of Donald Trump, we cannot assume that the revelation of a twelfth-rate mind will cause a person to live the life of a Darwinian loser.
[1] See Empire of the Summer Moon, S.J. Gwynne
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