Culture-gene coevolution and language

Simon Fisher and Matt Ridley, in a recent essay in Science, discuss the relationship between the genetic mutations that distinguish humans and other primates and the behavioral traits that those mutations may underlie Fisher:Ridley:2013. They draw upon the lactase persistence example, in which the dietary "niche" of milk consumption must have been present before the causal mutations for lactase persistence were selected in human populations. The essay mistakenly lumps alcohol "tolerance" of Europeans relative to Asians in with lactase persistence as an example of adaptation after the fact (citing Guns, Germs and Steel for this fact); in reality, the Asian flushing reaction is the novel trait, apparently driven by natural selection on a new mutation within Asia.

In any event, the general point is that several Holocene examples show that humans have adapted to new cultural innovations and environmental pressures only after those ecological changes were present.

FOXP2 is not the only gene associated with the human revolution (3). However, it illustrates that when an evolutionary mutation is identified as crucial to the human capacity for cumulative culture, this might be a consequence rather than a cause of cultural change (8). The smallest, most trivial new habit adopted by a hominid species couldif advantageoushave led to selection of genomic variations that sharpened that habit, be it cultural exchange, creativity, technological virtuosity, or heightened empathy.

This seems so uncontroversial that one may wonder why it needed to be written. But there has unfortunately been a long tradition in which some archaeologists and linguists have imagined that language emerged upon a single macromutation. The entire history of analysis of FOXP2 has underlined this assumption, as it has attained outsized visibility due to its interesting pattern of evolution. People obsess about whether it is "the" language gene. The question presupposes a saltational model of language evolution.

In this respect, the well-known examples of Holocene human adaptations may not be ideal analogies for language evolution. Lactase persistence, the Duffy null blood type, and the flushing reaction are all cases where one large-effect mutation really was strongly selected in response to a novel environmental pressure. But those examples are surely the tip of the iceberg when it comes to the full picture of recent adaptation. Most human phenotypes are complex, involving many genes, and evolution of such traits in response to Holocene environmental changes almost certainly involved changes in the frequencies of standing genetic variants of much weaker effect. It is difficult for us to discover these gene networks, because of the small effect sizes and deeper history of the variants. But that pattern of multigenic adaptation must be much more likely to characterize language evolution.

Did talking come first? A true coevolution would have bootstrapped behavior, learning and genetic adaptations together.