No study has led to the isolation of true human sex pheromones, although various researchers have investigated the possibility of their existence. Pheromones, in general, are secreted chemical substances by organisms that trigger a social reaction in the same

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. Sex pheromones are a special type of olfactory signal, produced to attract the opposite sex, to encourage mating or to perform some other function closely related to

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

. While humans are highly dependent upon visual cues, smells can also play a role in sociosexual behaviors. An inherent difficulty in studying human pheromones is the need for cleanliness and odorlessness in human participants. Experiments have focused on three classes of putative human sex pheromones: axillary steroids, vaginal aliphatic acids and stimulators of the vomeronasal organ. Axillary steroids are produced by the

testicle A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is Homology (biology), homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of Androgen, androgens, p ...

ovaries The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

, apocrine glands and

adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer adrenal corte ...

s. These chemicals are not biologically active until puberty when sex steroids influence their activity. The activity change during puberty suggests that humans communicate through odors. Several axillary steroids have been described as possible human pheromones: androstadienol, androstadienone, androstenone, androstenol, and androsterone. Androstenol is the putative female pheromone. In a 1978 study by Kirk-Smith, people wearing surgical masks treated with androstenol or untreated were shown pictures of people, animals and buildings and asked to rate their attractiveness. Individuals with their masks treated with androstenol rated their photographs as being "warmer" and "more friendly". The best-known case study involves the synchronization of

menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eg ...

s among women based on unconscious odor cues, the '' McClintock effect'', named after the primary investigator, Martha McClintock, of the University of Chicago. A group of women were exposed to a whiff of perspiration from other women. Depending on the time in the month the sweat was collected (before, during, or after ovulation), there was an association with the recipient woman's menstrual cycle to speed up or slow down. The 1971 study proposed two types of pheromones involved: "One, produced prior to ovulation, shortens the ovarian cycle; and the second, produced just at ovulation, lengthens the cycle". However, recent studies and reviews of the methodology have called the validity of her results into question. A 2013 meta-review of existing studies showed that the syncing of ovarian cycles likely did not exist. Androstenone is postulated to be secreted only by men as an attractant for women and is also thought to affect their mood positively. It seems to have different effects on women, depending on where a female is in her menstrual cycle, with the highest sensitivity to it during ovulation. In 1983, study participants exposed to androstenone were shown to undergo changes in skin conductance. Androstenone has been found to be perceived as more pleasant to women at a woman's time of ovulation. It is hypothesized that this may be a way for a male to detect an ovulating female who would be more willing to be involved in sexual interaction.

References

Bibliography

* * Jacob, Tim J.C. (2005) A critical review of the evidence for the existence (1) human pheromones and (2) a functional vomeronasal organ (VNO) in humans
School of Biosciences, Cardiff University {{Pheromones and pherines Sexual attraction">Human pheromones"> Sexual attraction

See also

References

Bibliography