Nov. 8, 2021 -- Our moral reaction to getting high or a night of casual Netflix and chill -- a modern euphemism for having casual sex -- may trace in part to our DNA. A new study suggests that our genes could shape our views on these behaviors just as much our environment does.

Social scientists have typically assumed that our morals are shaped by the people most present during our childhoods -- like our parents, teachers, and friends -- and what we experience in our culture -- whether from books, television, or TikTok.

Results of the new study, published in Psychological Science, suggest that genetics may at least partly explain our moral reactions.

The researchers surveyed more than 8,000 people in Finland, all either fraternal or identical twin pairs or siblings. They asked participants about their views on recreational drug use and sex outside of a committed relationship. Twin studies help scientists tease out the role of nature versus nurture because identical twins usually have the same DNA sequences, but fraternal twins have only about half of their DNA in common.

Investigators compared survey responses to see how much shared DNA explained negative opinions about casual sex and drug use and how much could be attributed instead to a shared environment or unique experiences between the twins.

Views on sex and drugs were at least 40% attributable to shared DNA and the remainder attributable to unique experiences, the study found. Views on sex and drugs were also strongly linked, with considerable overlap in opinions about each category.

One limitation of the work is common to twin studies in general. These studies cannot distinguish whether certain genes are activated by a shared childhood environment or if some gene variants drive the choice of certain types of environments.

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News release, Association for Psychological Science.

Psychological Science: “Sex, drugs, and genes: Moral attitudes share a genetic basis.”

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