The conclusion from a study I blogged about a few days ago is that preference for blue-eyed women is an evolved adaptation that allowed blue-eyed men to detect extra-pair paternity by children’s eye colour and so protect themselves from cuckoldry.
Why is this so important? Is cuckoldry so common in humans? Several studies support the idea that women have been rather promiscuous throughout our evolutionary history. The reason for this might be the fact that promiscuous females give birth to healthier young. Indeed, an article in January’s issue of Current Biology brings us further evidence of this: a small marsupial mammal ‘antechinus’ females who are more promiscuous sire healthier offspring. The reason is, when the female is inseminated by sperm from several males, the most competitive sperm fertilizes the egg. It just happens that the males who have more competitive sperm also father healthier offspring; they are better quality males, genetically speaking.
So, one might wonder if there is sperm competition in men, and indeed there is some support for this idea. Interestingly, women also actively choose their partners. This may have biological input as well. Not only visual features such as symmetry of the man’s body and face but also olfactory cues play role in whom a woman chooses as her sexual partner. There is some evidence that women can smell the differences in underlying immune system genes such as HMC genes in men and also prefer men as mates according to those different genotypes.
However, so far there has been little real evidence that there are pheromones in humans. Pheromones are molecules produced by one individual which can alter the behaviour of another individual. However, new research published in the Journal of Neuroscience successfully identified a potential pheromone from men’s sweat. A molecule, androstadienone, found in men’s sweat, sperm and saliva has been found to have an effect on women after they sniff it. This effect is an increase in levels of a certain hormone-cortisol. This further resulted in women feeling well and sexually aroused.
So there is a whole set of characters, from eye colour to smell, that can influence mate choice in humans. Evolutionary biology is a tool to make sense of all these different bits and pieces of peculiarities in our sexual behaviour.