Nothing is simple in biology


A female fly’s previous sexcapades can have a profound effect on how her future children look, redefining the way scientists think about inheritance in insects.

Researchers at the University of New South Wales in Sydney, Australia, discovered that a mother’s first sexual partner can determine the size of her later offspring, even if he didn’t sire them. This odd evolutionary twist is caused by a secret compound in sperm.

“It is strange and certainly unexpected,” said Angela Crean, an evolutionary ecologist at the university who co-authored the study. “We thought genetics is how inheritance works, but that’s just one mechanism of inheritance.”

Everyone knows the story of how babies are made. Sperm meets egg and creates a new life-form, which is half father and half mother. However, there are environmental factors that affect the development of the fetus, like smoking (in humans) and other chemical exposures in the womb.

In the case of the fly, semen is an environmental factor that holds the key to a baby fly’s size—whether or not the baby is related to the fly that supplied the semen, according to a new study published in Ecology Letters.