The paper published Wednesday in Science Advances found evidence for genetic variations that contribute to both bisexual attraction in men and a heightened appetite for risk.
Those findings help resolve a paradox at the heart of evolutionary theory — while also raising difficult new questions about the genetic roots of same-sex attraction.
For generations, evolutionary biologists have seen homosexual or same-sex attraction as a hole in evolutionary theory, as it is an at least somewhat inherited trait that also leads those who have it to have fewer children.
“So if you put these two things together, it doesn’t make sense,” lead author Jianzhi Zhang of the University of Michigan told The Hill.
“Those genes lead to fewer children, so that means they are being selected against in the population by natural selection. So gradually, they should just disappear from the population. So why do they still exist?”
That’s a question that goes far beyond the world of human sexuality. Same-sex attraction and behavior are widespread across the animal kingdom, from male gentoo penguins co-raising eggs, sex among all-male bachelor packs of gorillas and “seasonally bisexual” flying fox bats.