Why are human faces so variable compared to other animals, from lizards and penguins to dogs and monkeys? Scientists analyzed human faces and the genes that code for facial features and found a high variability that could only be explained by selection for variable faces, probably because of the importance of social interactions in human relationships and the need for humans to be recognizable.
MORE: http://www.sciencedaily.com/releases/2014/09/140916112240.htm
See also...
Our brains judge a face's trustworthiness, even when we can't see it
http://www.sciencedaily.com/releases/2014/08/140805220718.htm
Society bloomed with gentler personalities, more feminine faces: Technology boom 50,000 years ago correlated with less testosterone
http://www.sciencedaily.com/releases/2014/08/140801171114.htm
