Behavior Genetics: From Heritability to GWAS and Back Again

Investigations of the genetic underpinnings of human behavior are advancing rapidly. Before, twin and family studies assessed the influence of genetic differences on behavioral traits, such as intelligence, depression, and schizophrenia. Decades of quantitative genetics evinced one provocative-yet-indisputable empirical fact: the more genetically similar, the more phenotypically similar. It eventually became the First Law of Behavior Genetics: all behavioral traits are heritable. But what does it mean for a trait to be heritable? The advent of fast and cheap DNA sequencing technology provides new approaches to answering this old question. Genome Wide Association Studies flag small genetic differences — known as Single Nucleotide Polymorphisms — as statistically associated with behavioral differences. Polygenic Risk Scores allow researchers to estimate the quantity of genetic differences relevant to specific traits. Genome Complex Trait Analysis allows researchers to calculate a new 'molecular heritability' estimate, which is grounded strictly in DNA differences. The field of behavior genetics, which started somewhere with quantitative heritability, has now returned back to a new and poorly understood, 'molecular heritability'. This symposium proposal brings philosophers, biologists, and behavior geneticists together to reassess the philosophical landscape of human behavior genetics, in light of the latest theoretical and technological advancements.