There are likely to be others, but that has not yet been established. Pheromones' role in animal life is well described. For example, when two ants meet on a trail and pause to rub antennae, they are passing pheromones back and forth to ascertain each other's species and, often, their colony identity, says William C. Agosta, a chemist at Rockefeller University in New York. Higher animals, such as mammals, have individual pheromones or special combinations of these chemicals that signal their identity, enabling babies to recognize parents and vice-versa, Agosta says. Although research over the past 2 decades has hinted at the existence of human pheromones, some scientists have remained unconvinced that people harbor and react to them, says Charles J. Wysocki, a neuroscientist at Monell Chemical Senses Center, a nonprofit research facility in Philadelphia.
Several puzzles remain.
The chemical structure of these pheromones is unknown. Moreover, studies have failed to determine whether men exude pheromones that affect fertility. As to why women radiate these pheromones, one theory holds that simultaneous ovulation in a group of women helped in prehistoric times to promote genetic diversity, since one man couldn't impregnate everyone in the group. Aside from affecting the hormones that induce ovulation, no one knows what reactions human pheromones trigger. In insects, the answer to that question has proved complicated, he says.