The oral stimulation of the penis, especially to orgasm.
“Fellatio” is defined as the oral stimulation of the penis, especially to orgasm. The word derives from the Latin “fellatus,” meaning “to suck.” Fellatio is a common form of foreplay in sexual relationships as well as a sexual end in itself. The practice has been documented in animals, in ancient societies, and in contemporary primitive societies, strongly implying that it has some form of evolutionary benefit.
Flying foxes and fruit bats have been documented to engage in fellatio, with sex lasting longer between fruit bats if the male is first fellated (Tan et al. 2009). The Indian Kama Sutra, written in the first century AD, explores the subject of fellatio in considerable detail. The author believed that it was commonly practiced by promiscuous women, that it was a ritually unclean practice, and that those who were known to engage it in were often shunned by civilized society. Homosexual fellatio is depicted on the Greek Attic red figure kylix, which has been dated to around 510 BC. Anthropologists have recorded fellatio among assorted tribal groups. The initiation rite of passage of the Sambia, of Papua New Guinea, involves prepubescent boys, aged between 7 and 10, daily fellating older males and swallowing their semen (Soble 1997, p. 124).
Fellatio and Evolution
There is much debate on how the practice of fellatio may have evolved. A number of studies have indicated direct benefits in terms of fertility and health. The first benefit is that oral sex, as foreplay, makes fertilization more likely. Tan et al. (2009) suggest that fellatio-related foreplay increases the degree to which the penis is lubricated, increases the size of the erection, and increases the length of intercourse, heightening the level of secretion from the pituitary gland. All of these factors, they argue, increase the likelihood of successful fertilization. Secondly, the same researchers suggest that saliva may reduce the risk of passing on certain sexually transmitted diseases, ensuring a healthier partner and offspring.
Thirdly, research has shown that when a woman regularly swallows her partner’s semen, her immune system becomes used to it to, making it more likely that the mother’s immune system will accept the proteins in the father’s semen. It has been found that many miscarriages, or preterm births, occur because the mother’s immune system treats these proteins, in the fetus, as foreign bodies. It has been found that 82% of women without preeclampsia (a condition marked by high blood pressure during pregnancy which can lead to miscarriages and preterm births) regularly practiced fellatio on their partner, but only 44% of those with preeclampsia did (Koelman et al. 2000). Accordingly, fellatio aids the birth of offspring who are more likely to survive.
Thus, fellatio appears to have evolved, in part, because it is associated with fertility and health. However, parallel dimensions of its evolution have been suggested. Pham and Shackleford (2013) proposed that infidelity detection may be one reason why women may wish to fellate their partners. In a context of relatively poor cleanliness, it possible that cues of infidelity could be unconsciously picked up through tasting the penis. Pham et al. (2015) found that both men and women reported being more satisfied with their relationships the more oral sex they had and length of relationship was moderately inversely correlated with frequency of and length of oral sex. Thus, part of the purpose of oral sex would appear to be simply bonding. Indeed, giving oral sex within a relationship has been shown to be positively associated with Agreeableness (Pham et al. 2015), which is itself associated with the capacity to foster strong bonds.
Fellatio and Religion
This bonding dimension would be consistent with the practice of fellatio by children in Papua New Guinea on older males. The practice is likely to create a bond between the two males, inducing the older male to assist the younger one in times of need. In this sense, it can be seen to elevate in-group cooperation, and it has been found that internally cooperative groups, all else being equal, tend to triumph over less internally cooperative groups (see Sela et al. 2015). In addition, among the Manchu people of China, a mother may show affection to her son, under the age of 2 years, by kissing his penis or putting his penis in her mouth (e.g., Renteln 2004, p. 243, footnote 49).
Moreover, it has been argued that, to a great extent, religion should be understood as an evolutionary strategy which renders individuals and groups more likely to survive under conditions of natural selection (e.g., Sela et al. 2015). Consistent with this, many forms of behavior which religious groups promote as divinely mandated have been shown to ultimately promote selection (Sela et al. 2015). Homosexual fellatio in New Guinea tribes – among heterosexual males – reflects a central part of the tribes’ belief system. They believe that young boys do not yet have semen and so they must acquire it from other men via fellatio and acquire as much of it as possible.
Fellatio, Group Differences, and Life History Strategy
A number of studies have found group differences in the extent to which fellatio is performed. If a significant dimension to fellatio is bonding, then this is to be expected. Rushton (2000) has argued that different racial groups vary in their life history speed, in a model known as Differential K. Fast life history (LH) strategists, evolved to a plentiful but unstable ecology, tend to invest more resources simply in reproduction. As life is unpredictable, they are evolved to seek out and copulate with as many fertile and healthy people as they can, investing little energy in their partners and hoping some offspring survive. Slow LH strategists, in a harsh yet predictable ecology, reach the carrying capacity for their group and start competing to a greater extent with each other. This selects for quality over quantity. Accordingly, they invest more energy in the nurture of their (smaller number of) offspring and more energy in their (smaller number of) sexual partners, to ensure their offspring’s survival. They create strongly bonded units. Accordingly, to the extent that fellatio is a matter of bonding, there should be group differences in its extent.
Rushton argues that sub-Saharan Africans are, on numerous measures, faster life history strategists than are Caucasians. Pham et al. (2015) have shown that Agreeableness (an aspect of a slow LH) positively predicts performing oral sex. The available studies on group differences in fellatio are consistent with this. They all find that African Americans, compared to Whites, are markedly more likely to have never been fellated or to have never fellated and they are more likely to have experienced or performed fellatio in a relationship only after the performance of penetrative sex, with this ordering being reversed in Whites (e.g., D’Souza et al. 2014). Unfortunately, studies comparing White and East Asian people are confounded by the fact that relatively young samples are employed (e.g., Meston et al. 1996) and East Asians appear to become sexually active later than White people (Rushton 2000).
Consistent with the idea that fellatio is associated with a slow LH, some research has found evidence that lower SES people are less likely to engage in fellatio than higher SES people (e.g., Schofield 1965). Black people in the USA, on average, have lower socioeconomic status than White people, so this may be the mediating factor. Lower SES people, on average, follow a faster LH strategy than higher SES people (Rushton 2000).
In terms of future research, it would be of great interest to establish in more depth the extent to which the practice of fellatio varies between different groups and thus the degree to which it may be a reflection of life history strategy. Related to this, it would be interesting to understand the origins of different attitudes to fellatio in different religions, as it may be that fellatio is more or less adaptive in different ecologies. Exploration of the Manchurian practice of briefly fellating babies and toddlers would also be interesting. In Western countries, young children are sometimes patted on the buttocks by adults, supposedly as a form of affection, or at least they have been historically. It is possible that there may be some evolutionary reason behind what some would regard as the unacceptable sexual touching of young children, though precisely what is a matter for future research to address.
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