In this lecture, we cover foundational topics in modern synthesis of behavioral genetics. The lecture starts with the nature-versus-nurture debate and its historical roots in tensions between American psychologists and European ethologists (fueled in part by geopolitical contexts at the time). Ultimately, we cover the more modern, integrative, "nature-via-nurture" perspective where phenotype reflects effects of both genes (potentially many genes) and their interaction with the environment ("GxE"), and biologists are interested in understanding the relative contributes of both (e.g., with "heritability" quantifying the relative contribution of genotypic variation to phenotypic variation in a population). We then discuss different historical fields that have contributed to the modern synthesis and examples of what they have contributed. That gives us an opportunity to discuss phenomena identified in evolutionary biology that help to explain the counterintuitive observation that, for reasons unrelated to genetic drift, many traits that have an apparent fitness cost are still maintained (or at least not purged) in a population. We close looking forward to a unit on behavioral genetics that will introduce methods that behavioral ecologists use to try to separate genetic and environmental effects as well as quantitative tools for better understanding which genes contribute in complex ways to any particular phenotype/trait.
Topic highlights:
- historical nature-versus-nurture debate and contributions to its origins in ethology-vs-behaviorism
- definitions of gene, allele, genotype, character, trait, phenotype, and expression (as in "gene expression" and "phenotypic expression")
- nature-via-nurture perspective and "GxE to P" ("G by E to P" or simply "G by E")
- definition of "epistasis" and its interpretation as GxGxE
- definition of "epigenetics" and its interpretation as GxExE
- rough definition of "heritability"
- foundations of the modern synthesis of the genotype-to-phenotype map, with focus on:
- domestication/artificial selection
- phylogeny (including definition of a "cladogram")
- quantitative and biometrical genetics
- definition of "quantitative trait"
- evolutionary and population genetics
- definition of "ecotype" as a genetically (and generally geographically) distinct subpopulation that has been locally adapted to its home environment
- ecotypes are a product of natural selection (whereas the "founder effect" and "genetic bottlenecks" are related to genetic drift)
- discussion of notable evolutionary processes that maintain traits for counterintuitive reasons, including:
- correlated characteristics
- phylogenetic inertia
- the handicap principle
- disruptive (or diversifying) selection
- definition of "ecotype" as a genetically (and generally geographically) distinct subpopulation that has been locally adapted to its home environment
Important terms: G by E (GxE), G by E to P (GxE->P), GxGxE, GxExE, epistasis, epigenetics, ecotype, gene, allele, genotype, character, trait, phenotype, gene/phenotypic expression, genotypic variance, phenotypic variance, heritability, quantitative trait, artificial selection/breeding, phylogeny, cladogram, correlated characteristics, phylogenetic inertia, handicap principle, disruptive/diversifying selection
