Romeo and Juliet. Princess Leia and Han Solo. Brad and Angelina. They all have that electric sexual connection. From literature to the silver screen to the high school dance floor, attraction, desire and chemistry are universal. But still for most of us, this intangible vibe remains mystifying.

Start with the fact that we are wired with a drive to pass our genes to future generations. This is, after all, the root motive for mating. Guided by this motive, scientists are now beginning to reveal the subtle, yet determined, cues of sexual attraction. Body proportion and the symmetry of facial and body features serve as visual proxies for good genes and high fertility, the holy grails in the drive to procreate. Skills on the dance floor, sweaty tee shirts and sultry voices also play curious roles in the hunt for a mate.

With that, a new era in reproduction studies has emerged, untangling this complicated question of chemistry. But the field, so fundamental to human evolution, has been fraught politically.  Evolutionary studies started in the 1930s, said Fisher, but quickly fell out of favor during WWII and its aftermath, when biological differences were used to buttress anti-Semitism and other forms of racism.

Then in the 1960s, primatologist Jane Goodall studied chimpanzees and realized they appeared “unnervingly human,” said Fisher. 

Chimps, our closest animal relatives, who are completely separate from human culture, also feel love, anger and desire. This proved something other than social influences molded our behavior.  These emotional traits were genetic, Goodall’s research revealed.