Faces and genes

According to psychologist Lisa DeBruine people tend to choose friends who look like them and may do so in order to promote the interests of their genes:

Dr DeBruine, of McMaster University, Canada, said previous research had shown that people were more likely to trust others who looked like them.

In one of her previous studies she found people playing a two-person monetary investment game over the internet while viewing a picture of the "second player" were more likely to trust this player if the picture was digitally morphed to resemble them.

She believes it may be possible that we are evolved to place greater trust, and to have greater affection for, people who look as though they may be related to us because the chances are higher that they share the same genes as us.

By forging a bond in this way, it could help these people to thrive, and thus, in evolutionary terms, to pass their genes down to the next generation.

Professor David Perrett, of the Perception Lab at St Andrew's University, told BBC News Online: "It is likely that people who look similar to ourselves share our genes, and it makes sense to help the cause of these individuals because, in effect, we are helping our own genes."