Tech

Study: Past Sex Partners Could Influence What Your Kids Look Like

Alex Olson Contributor

Hold off on that DNA test — there could be another reason your kids look like your ex.

Scientists at the University of New South Wales have discovered a new form of non-genetic inheritance and demonstrated for the first time that a woman’s past sex partners can influence the appearance of subsequent offspring with a different man.

The theory that children are physically influenced by all of their mothers’ sexual partners dates back to ancient Greece, where it was an accepted fact, but genetic advances in the 20th century put the idea to rest — until now.

UNSW scientists Dr. Angela Crean, Dr. Anna Kopps and Professor Russell Bonduriansky manipulated the size of male flies and then studied their offspring. They found that the young tended to be around the size of the first male their mothers had mated with, not the second male who was their biological father, ScienceDaily reports.

“Our discovery complicates our entire view of how variation is transmitted across generations, but also opens up exciting new possibilities and avenues of research. Just as we think we have things figured out, nature throws us a curve ball and shows us how much we still have to learn,” said Dr. Angela Crean, the study’s lead author.

The study, which was published in the journal Ecology Letters, proposes that this strange coincidence is due to molecules in the seminal fluid of the first male mate being absorbed by the immature eggs of the female, and then influencing the development of the second male’s offspring. Dr. Crean reported that researchers “found that even though the second male sired the offspring, offspring size was determined by what the mother’s previous mating partner ate as a maggot.”

The study has raised many questions about the transmission of certain traits. Genetic transmission could be just a part of what makes us who we are.

“We know that features that run in families are not just influenced by the genes that are passed down from parents to their children. Various non-genetic inheritance mechanisms make it possible for maternal or paternal environmental factors to influence characteristics of a child,” says Dr. Crean.

Researchers add that it is unclear how this discovery will relate to the mating habits of other species, humans included.

“Our new findings take this to a whole new level — showing a male can also transmit some of his acquired features to offspring sired by other males, but we don’t know yet whether this applies to other species.”