Pheromones
During the past century research amply demonstrated that pheromonic communication is found
Women in dorms or close girlfriends often menstruated at the same time.
Women who are cloistered away from men (e.g., in a boarding school) enter puberty later than women who are around men.
When a man gets involved with a woman for any length of time, his facial hair starts to grow faster than it did before.
Mothers recognize the odour of their newborn children, and vice versa, so some doctors are experimenting with giving children bursts of their motherís odour, along with the anesthetic, during operations.
Babies can smell their mother entering a room, even if they cannot see her.
Mothers of school-age children can pick out T-shirts worn by their own child. (This is not true for fathers, who do not recognize the smell of their infants, but men can determine whether a T-shirt has been worn by a male of female.)