Fly Family Feud: Babies Look Like Mom’s Ex Mates

All flies look alike to me but not to their parents. That’s why some papa flies get suspicious when one or a thousand of their offspring look more like their mama’s ex-boyfriend. They had to believe her excuse that it was just a coincidence … until now. A new study found that a female fly’s previous sex partners can pass their physical characteristics down to her offspring from other males.

The idea that children can inherit traits from various mates of their mother is called telegony. Aristotle talked about it and it’s been used throughout history as a reason for women to avoid having sex with men of lower classes or different races. It was a factor in the controversial marriage in 1361 of Edward, the Black Prince, to Joan, the Fair Maid of Kent, who had been previously married and might pollute the royal lineage. While the concept was never proven, the Nazis professed that a woman who had sex with a non-Aryan could never have a “pure” Aryan child again.

Led by Dr. Angela Crean, researchers from New South Wales University manipulated the size of male flies through diet, then mated them with immature females. When the females matured, they mated them again with males of varying sizes and the results were surprising, according to Dr. Crean.

We 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. 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.

The researchers believe molecules in the seminal fluid of the first sex partner were absorbed by the female’s immature eggs and then impacted the growth of offspring of a different partner.

As if dating isn’t complicated enough, Dr. Crean wouldn’t positively rule out the possibility that this could also happen in humans.

There is no evidence of such effects in humans, but there has not been any research on this possibility in humans. There is a potential for such effects in mammals. For example, there is a lot of foetal DNA in maternal blood during pregnancy, and this could potentially play a role in such effects. There is also evidence in mammals that seminal fluid affects offspring development, so semen from one male could potentially influence the development of eggs fertilized by another male (which is what we think is happening in flies).

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