Most anthropologists date the appearance of anatomically modern Homo sapiens to approximately 150,000 years ago. It was at about this time that the skeletal structure of Homo becomes indistinguishable from modern humans. This does not mean, however, that human evolution simply stopped; evolution encompasses changes not only to skeletal structures but also to brain chemistry, neural connections, immune functions, digestive abilities, and genes that code for behaviors. Humans have continued to evolve over the last 150,000 years, despite relative stability in skeletal structures.
Some anthropologists, such as John Hawks, contend that human evolution has in fact accelerated during this period of time. Professor Hawks has several excellent blog posts on these topics, beginning with “Human Evolution Stopping? Wrong, Wrong, Wrong” and “Why Human Evolution Accelerated.” Another example of recent human evolution comes from a study of high altitude adaptations by Tibetans, discussed by Nicholas Wade last week in an article titled “Scientists Cite Fastest Case of Human Evolution.”
Given all this evidence of recent human evolution, I began thinking about the story group level selectionists tell regarding the evolution of religion. With minor variations, this story involves the appearance of shamans who developed rituals that made groups more cohesive and prosocial. In several posts, I have pointed out the problems with this story.
Although this story may not be valid for the paleolithic, it is possible that group level selection and religion began having genomic effects after the Neolithic Revolution. The earliest organized religions arose with the appearance of the earliest agricultural societies. Increased fertility within these communities could have impacted the genome, and some of the selection could have targeted those who are inclined toward religious belief and participation.
If this in fact occurred, it will — for two reasons — be exceptionally difficult to identify at the genetic level. First, there is no “religion” gene. Religious behaviors are complex and involve many different brain functions. We can expect, therefore, that many genes are involved and we will never identify just a few that usually result in religiosity. Second, organized religions are powerful cultural institutions. Teasing out which aspects of religiosity are due to cultural imprinting-patterning and those which are due to genes will prove to be an impossible task.