Scientists of the University of East Anglia in Norwich, UK, lead by Tracey Chapman, found that male fruit flies selectively alter the chemical make-up of their seminal fluid. This means that their semen can alter both the bodies and soemtimes even the behavior of females. “It came as a real surprise,” says Chapman.

Findings presented at the Society for Molecular Biology and Evolution conference in Vienna, Austria, last week, state that one of the proteins in the seminal fluid can be considered a “master regulator” of genes. Females exposed to it have a wide range of changes in gene expression.

Chapman believes that this kind of seminal signalling is widespread in people, pigs, mice and so forth. A question is raised as to whether it can produce behavioral changes in female mammals such as the ones seen in fruit flies.

There’s a chance it can when looking at previous studies. For instance a 2002 study based on a survey of 300 students found that women whose partners did not use condom protections were less likely to be depressed. Furthermore, depression is treatable with artificial-semen suppositories. The same result of the initial study was later replicated at the State University of New york at Albany.

Chapman feels it is possible that semen’s effects could extend beyond reproduction.