A group of men had sperm samples taken and pictures taken of them. Their sperm was tested and separately they were rated for looks by a group of women. The men judged to be better looking had higher quality sperm on average.

Maria Sancho-Navarro, a researcher at the University of Valencia, said men were generally rated as being attractive if they had "symmetrical" faces.

"The women found that men with symmetrical faces were more attractive. These men had eyes, ears and nose that were more symmetrical than the other men," she told BBC News Online.

This is not too surprising. The ability of women to judge the healthiness of potential mates would have been of considerable selective value. Many problems that occur during fetal development cause asymmetry in the resulting organism. So for humans to find facial symmetry as an important component in judging attractiveness is not surprising.

It would be interesting to know is whether people with symmetrical faces have longer life expectancies.

Also, on a related note, another study found that men who were shown pictures of women to rate their attractiveness and separately heard the same women sing without seeing their faces tended to find the women with the more pleasing voices to have more attractive faces on average. Is the sound of a voice another measure of the quality of embryo development?

The New Scientist coverage of the sperm quality and physical attractiveness study is here.