Meanwhile, another team is zeroing in on the factors that we initially find attractive in a mate, and have discovered that earlobes and elbows may be the most important things you can show off across a crowded room. The more symmetrical a man's face and body are, the more likely he is to have multiple sexual partners and bring women to orgasm - though he is also more likely to be unfaithful. For women, facial symmetry - including ears - is a good indicator of attractiveness to men. In both sexes, there was a link to higher intelligence.
"It's an evolutionary thing, a genetic marker," said Professor Randy Thornhill, of the University of New Mexico. "The degree of symmetry of the body shows how well an individual's genes deal with the insults that life throws out. It may be the best measure that we have of the quality of our genes. It's a health certificate, which is why it's attractive to us."
The subdivisions of love, though, appear to be the same across the divides of culture, sex and sexual preference, according to Helen Fisher, an anthropologist at Rutgers University in New York.
She found that people exhibit a general sex drive - lust - followed by a more particular attraction to one mate, in which the object of infatuation keeps popping into mind. After that, love turns into "attachment".
She thinks that different body chemicals make us feel that way: hormones for the sex drive, Ecstasy-like chemicals to create the focus of attraction, and a related class, called monoamines, for the sated feeling that leads to long-term relationships.
Dr Fisher is trying to find the groups of neurones in the brain that are affected by the chemicals to cause these feelings. She is using infatuated students, who are quizzed about their love lives while sitting in a magnetic resonance imaging scanner, which shows active areas of the brain. "I have to spend hours talking to them," she said. "But they seem quite happy about it."Reuse content