UCLA’s Jonathan Flint debunks theory of “warrior gene” but signals possibility of predicting behavioral outcomes based on genetics

April 23, 2021

Jonathan Flint (UCLA behavioral geneticist, expert in the genetic determinants of depression and Depression Grand Challenge Executive Committee team member) shared background about the theory of the “warrior gene” in a blog post written for the Oxford University Press. Since the 1990s criminal defense lawyers have tried to argue that a mutation in the “warrior gene” mitigates responsibility for aggressive behavior. Flint highlights a 2021 New Mexico Supreme Court case which definitively ended the argument that a single gene mutation determines overall behavior.

While there isn’t a single gene (like a “warrior gene”) that can be blamed, there still is the possibility that we can blame someone’s genetic constitution in aggregate. Flint argues that this is not the end for genetic determinism. Almost all behavior is heritable to some extent – it arises from the combination of thousands of individual genetic variants, which individually have a miniscule affect (.01%). Flint highlights that scientists are getting better at predicting behavioral outcomes from the combination of variants (a technique that is central for the Depression Grand Challenge to understand the causes of depression). While a single “warrior gene” argument will no longer fly, there is still a possibility that in the future lawyers will be able to argue, “don’t blame my client, he couldn’t help himself, it was all in his genes.”
Read more at Oxford University Press’s Blog.