Facial attractiveness and species recognition: an elementary deduction?

The perception of human beauty has been traditionally considered a purely cultural phenomenon. Although the concept of sexual selection was originally introduced by Darwin, only during the last two decades, due to the upsurge of computer graphics, has it become possible to unravel a deep, conserved, biological component in the perception of facial attractiveness. It has been proposed that the human brain is endowed with "prototypes" or "templates" used as references for judging real faces. Some characteristics of an "ideally beautiful face" such as averageness, symmetry, youthfulness and sex-specific traits have been described. These characteristics have been discussed as signs of heterozygosity, resistance to parasites, health, developmental stability and fertility. Theoretical and field research have shown that sexual selection can drive sympatric speciation. Paleoanthropology has clearly shown that archaic Homo sapiens has coexisted with H. neanderthaliensis and paleogenetics has shown that no interbreeding occurred between the two species. Sexual selection might have been one of the mechanisms that led to the reproductive isolation of H. sapiens. If this hypothesis is correct, a "beauty template" should assign higher fitness to facial features that enhance the differences between the average face of H. sapiens and the face of its extinct relatives. This hypothesis is discussed and compared with the other existing hypothesis on evolution of human attractiveness.