Body odour and sexual attraction
[3][4] Humans can make use of body odour subconsciously to identify whether a potential mate will pass on favourable traits to their offspring.
Body odour may provide significant cues about the genetic quality, health[5] and reproductive success of a potential mate.
[6][7] Body odour affects sexual attraction in a number of ways including through human biology, the menstrual cycle and fluctuating asymmetry.
The major histocompatibility complex genes are important for the immune system, and appear to play a role in sexual attraction via body odour.
[9] The olfactory epithelium is a thick yellow/brown structure, about one inch square, located in the upper nasal cavity of the human nose.
[14] Experiments have focused on three classes of putative human sex pheromones: axillary steroids, vaginal aliphatic acids and stimulators of the vomeronasal organ.
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.
This includes the role of the major histocompatibility complex (MHC), the human leukocyte antigen (HLA) and their different heterozygotic variations.
[2] The MHC (major histocompatibility complex) is a group of genes essential for the immune system, playing an important role in immunological recognition.
[26] Unique body smells are heavily influenced by MHC; these olfactory cues are probably involved in mate choice and preferences.
An evolutionary explanation is that females are attracted to males with MHC alleles different from their own, to provide their offspring with a stronger immune system.
Over thirty olfactory receptor genes have been located at the HLA class I region,[36] which presents peptides from inside the cell to be destroyed by the immune system.
Studies have shown that women who are at the most fertile stage of their menstrual cycle prefer the smell of men that have higher testosterone levels.
Studies[42] showed that MP2 has the strongest response produced by female vomeronasal organ (VNO), which is the first stage of the olfactory system.
[4][46] Olfaction, therefore, transmits information relevant to human mate selection, through which men are capable of detecting shifts in women's fertility.
[47] Hormonal fluctuation across the menstrual cycle explains temporal variation in women's judgment of the attractiveness of members of the opposite sex.
This is due to the psychological processes that shape the formation and maintenance of human romantic relationships, which are influenced by variation in hormonal levels.
[4] Meanwhile a similar study of slightly larger sample size failed to find a significant difference between males' ratings of ovulating and non-ovulating females' odours.
[50] Another study found a significant difference in males' salivary testosterone levels after smelling the shirts of ovulating versus non-ovulating females.
FA acts as an index for measuring developmental instability as it provides a clear indicator of the possible environmental and genetic stressors affecting development.
[53] It is thought that having a preference for a symmetrical face offers some adaptive value as such symmetry may signal an individual's ability to cope with environmental challenges.
Whilst a vast number of studies have been conducted to investigate body odour and mating, research is now shifting in particular towards the effect of male scent to female sexual attraction.
Whilst males are influenced by body odour during selection, past research has demonstrated a significantly greater reliance on such cues by females.
Past research has shown that men using fragranced antiperspirants in videos were rated as more attractive by women than those in a placebo control condition.
A recent study aimed to investigate whether a dietary fruit and vegetable intake would influence female mate preferences.
Its results showed that subjects rated as most pleasant smelling were those with a higher fruit and vegetable intake, suggesting male body odour can be enhanced by diet to appeal to females.
[67] The sex pheromones of the silkworm moths can elicit responses in the male antenna at concentrations of only a few hundred molecules per square centimeter.
Mammal's pheromones are air-borne chemical substances released in the urine or feces of animals or secreted from sweat glands that are perceived by the olfactory system and that elicit both behavioral and endocrine responses in conspecifics.
These pheromones attract receptive sows, causing it to adopt a specific mating posture, known as standing, which allows the male boar to mount it and therefore copulate.
[82] The use of mixtures of compounds as pheromones is well documented in insects, research into male orchid bees demonstrates that specific odours mediate exclusive attraction within a species.
