3.7 How Evolutionary Theory Impacts Behavior

You may now be wondering, “Okay. I get all that. But how does evolution impact our behavior?” The answer is in the equation:

Genotype + Environment = Phenotype

Evolution does not directly impact genetics. Rather, selection pressures influence the reproductive success of phenotypes. If you happen to be a moth with white wings in an environment filled with white birch trees, you are more likely to survive and reproduce. In the meantime, the brown moths stand out on the white trunks of birch trees and are quickly eaten by local birds. If the color of the birch bark or type of trees in the area should change over time, the brown moths will eventually become the winners.

When evolution selects a phenotype, the genotype comes along for the ride. And simply put – behavior is a phenotype. Behavior is a series of responses to stimuli inside our bodies (e.g., hormones or metabolism) and outside our bodies (e.g., temperature, threats). And given the theoretical framework we received from Tinbergen, the exchange between phenotype and environment has been going on for quite some time.

Whitehead and colleagues (2019) provide a way for us to visualize this in their article, “The reach of gene-culture coevolution in animals.” Here the authors use bird song and orca predation habits to demonstrate how cultural transmission of a behavior (think “trends”) can result in modified selection pressures and/or population structures. This can create a feedback loop where individuals who adopt the trend are more likely to survive and reproduce, resulting in an overrepresentation of those individuals’ genes.

We will continue to reflect on gene-environment interactions throughout much of this book.