A biological signature inherited from Neolithic societies: Perspectives from gene-culture coevolution theory

Abstract : We wonder about the links between cultural and biological evolution, and about the impacts of culture on the selection processes which have taken place during human biological evolution.

Genetie and cultural transmissions can be jointly explored by the methodological framework of gene-culture coevolution (GCC) [2], which hypothesizes  that the individual's genotype  influences  his ability to learn, and that the selective pressures acting on the gene pool may be modified or initiated by a cultural trait and related behaviour  [7]. ln other words, depending on cultural transmission rate, cultural traits may spread all over a population and then create a strong selective pressure [1].

Here we would like to stress how a major cultural and economic shift such as the adoption of the Neolithic lifestyle has driven major biological changes in the European populations. Hence we will present two main biological adaptations related to a major change in our diet with the adoption of an economy of production: lactase persistence (LP) and amylase production.

Most adults worldwide cannot digest lactose (the main carbohydrate of milk) as their lactase (enzyme breaking the lactose) production drastically decreases after weaning [5]. According to GCC models, during the Neolithic, bearers of a mutation allowing a LP would have been selected by specific cultural conditions, which resulted from the consumption of dairy products  in  emerging  farming populations [7]. ln Europe before the spread of cattle breeding, the frequency of LP was extremely low among populations of hunter-gatherers. LP frequency would have become significant around 8000 years BP between central Europe and the Balkans, and would have spread through Europe by migrations of herders [6], to finally reach the rate that we know today [5].

People from today's agricultural societies possess more AMY1 gene copies than people from non agricultural societies, and their diet is much richer in starch. This gene produces salivary amylase, an essential protein in starch digestion, whose quantity is positively correlated with gene copy numbers. The copy  number of AMY1 would have been positively selected in those populations on a starchy diet. The initial human specific increase in AMY1 copy number is molecularly dated back 200 ky, hence it may have been coïncident with a dietary shift early in hominin evolutionary history [4].

The characterization of causal links between human genetic evolution and cultural traits promises to offer considerable insight into our evolutionary history.