Sure, he looks good. But how about his sperm?

That might not be such a ridiculous-sounding question, now that a new study has identified a link between men's facial attractiveness and the quality of their semen--with handsome, masculine-looking guys having slightly lower-quality semen than other men.

"To [the] best of our knowledge, this is the first demonstration of the phenomenon," study co-author Dr. Jukka Kekalainen, adjunct lecturer in the Centre for Evolutionary Biology at the University of Australia in Crawley, told The Huffington Post in an email.

The researchers have no readyexplanation for their finding, although previous research has shown that high testosterone levels can harm sperm production, the New York Daily News reported. And the finding seems to be at odds with the so-called phenotype-linked fertility hypothesis, which holds that females prefer handsome males because their offspring may enjoy hereditary benefits, such as better health and higher intelligence.

For the new study, which was published in the September 2014 issue of the Journal of Evolutionary Biology, a team of researchers from Spain, Australia, and Colombia performed semen analyses on 50 Caucasian students recruited from the University of Valencia.

Next, photos of the men's faces were shown to heterosexual men and women in their twenties, including Caucasians and blacks.

The women evaluators were asked to rate the men as if they were looking for a long-term mate. The men evaluators were asked to rate the men as they thought women would rate them.

The researchers also performed an "anthropometric analysis" of the facial characteristics of all 50 men, measuring the size of their eyes, the width of their cheekbones and nostrils, and other markers that previous research identified as masculine features. And finally the researchers compared the men's facial features with the motility (movement), morphology (structure), and concentration of the men's sperm cells.

In addition to looking for the link between masculine-looking faces and sperm quality, the researchers wanted to know if men's sperm quality was related to their handsomeness. "And we found that in fact it is," Kekalainen said in the email.

But does that mean women eager to find a mate capable of fathering children should be wary of handsome men? Maybe not--at least not until more research corroborates the finding.

As Kekalainen said in the email, "we would need more studies to demonstrate the causation and mechanism behind this finding...before giving any mating tips to the females."