CODEX Entry 8300: Human pheromones, the slave gene
The variety of molecules that animals have evolved to use as pheromones is enormous. The first pheromone was chemically identified in moths, in 1959, by the Nobel Prize winning German chemist Adolf Butenandt. Pheromone effects in mammals were first measured where the exposure to the urine of dominant adult male mice caused immature female mice to become sexually mature more quickly. They were sniffing up a nonvolatile protein pheromone, called darcin.
Research confirms that pheromone signals in mammals are absorbed through the olfactory bulb. The human olfactory bulb is significantly larger than that of Neanderthals. Sodium channels in Neanderthals also made them more susceptible to pain than Homo Sapiens.
Women who share a dormitory or are friends tend to synchronise or move to opposite menstrual cycles through pheromone signals. The shifts are not entirely understood as they vary amongst participants. However research in 1998 found that odourless compounds from the armpits of women in the late phase of their menstrual cycles accelerated the preovulatory surge of luteinizing hormone of recipient women and shortened their menstrual cycles. These hormones are released from the anterior pituitary gland and are responsible for managing the ovulation cycle. Compounds from the same donors which were collected later in the menstrual cycle (at ovulation) had the opposite effect, delaying the luteinizing-hormone surge of the recipients and lengthening their menstrual cycles. When female sweat is applied to the upper lip of other women, these women respond by shifting their menstrual cycles toward synchrony with the cycle of the woman from whom the sweat was obtained. Male underarm sweat has been shown to improve women’s moods and affect their secretion of luteinizing hormone, involved in stimulating ovulation. In 2013, androstadienone, a derivative of testosterone and a component of male sweat, was confirmed to act as a human pheromone, increasing attraction, affecting mood, cortisol levels and activating brain areas linked to social cognition, among other effects. Salivary testosterone levels were found to positively correlate with cooperative behaviour. After controlling for baseline testosterone levels, androstadienone was found to increase cooperative behaviour in the decision making tasks.
The majority of human-related pheromones come from the skin’s apocrine sebaceous glands, and are usually associated with sweat glands and tufts of hair. These glands are located everywhere on the body surface, but tend to concentrate in six areas: underarms, nipples, genitals, mouth, lips, eyelids, and outer ear. For eccrine glands, the source of watery perspiration and closely associated with pheromone release, the density in humans is 10 times higher than that of chimpanzees. The substances produced by these glands are relatively undetectable by the human nose; what we smell when we detect skin odor is not the fresh glandular secretions but rather the bacterial breakdown products of these glandular secretions.
Reactions to the human pheromones themselves range from fear; anxiety; aggression; increased or reduced libido, to well-being and relaxation.