[allison]

It's really very simple: Good appearance is a sign of good health (sick people don't usually look too good), which is why we humans and other animals are instinctively attracted to good looking mates--> they are more likely to be healthy and therefore more likely to help us have offspring that possess healthy and strong genes (half of which are ours). End result: we pass on our genes! That is the idea behind the concept of survival of the fittest.