American theoretical physicist Michio Kaku discusses the evolutionary psychology of human attraction in this fascinating, brief talk.
According to Kaku, evolution has slowed due to international travel and the mixing of genes, but has not stopped altogether as we still prefer other people that are healthy. Due to this, Michio Kaku states that evolution is constantly taking place on a one-to-one basis as we prefer people who are fit and healthy, which is interpreted as beauty.
A basic theory of evolutionary psychology is that we want healthy mates, and beauty is one way to judge the health of another person. Dr. Kaku gives the example of attempting to pick someone up at a bar: you can't do a blood test or physical examination, so you rely on markers for testosterone and estrogen such as large eyes and thick lips in females and large jaws and lower voices in males.