Bateman's principle is a principle in evolutionary biology which states that there is greater variance (or inequality) in reproductive success among males than females. That is, there are few males who have lots of offspring, but some males produce none (high variance), whereas most females reproduce, each with a similar number of offspring (low variance).
There is debate as to whether this principle holds true across the animal kingdom as a whole, or only under certain conditions in some species, however there is strong evidence that the principle holds for humans across a variety cultures, as well as a variety of other species like birds and even certain kinds of fungi. Moreover, the latest large study from 2016 testing the hypothesis did find a significant effect across many animal species, including humans.
Bateman suggested that females have greater parental investment because the production of eggs is more expensive than the production of sperm and the offspring has higher dependence on the mother. Males, on the other hand, can produce millions of sperm cells with little cost and can get away with reproducing with lots of females as they do not need to care for the offspring as much. Females are thus the limiting factor in reproduction rate, causing men to become less choosy (promiscuous), to have a high sex drive and to compete in order to gain copulation opportunities. Promiscuous males, in turn, cause females to be choosy in order to avoid promiscuous males of low genetic quality, exaggerating the effect. The result is that females reproduce much more reliably and few (alpha) males have a disproportionally high reproductive success.
The differential parental investment can explain a wide variety of phenomena:
- It explains the existence of hypergamy, i.e. the tendency that women prefer men of higher education, social or economic status, as a particular instance of choosiness and women's need to secure resources for their offspring.
- It explains why most historical achievements were done by men: Men, but not women, are biologically required to compete.
- It explains why humans are moderately polygynous across many cultures. 85% of all cultures have allowed polygyny to occur.
- It also explains why men have a higher cumulative demand for sex and hence why male incels outnumber female incels, e.g. social psychologist Roy Baumeister wrote about the Tragedy of the Male Sex Drive:
Given the mismatch between men's and women's desires, most men are doomed to experience chronic sexual frustration. […] [Men] are doomed to be horny.
Increased sex imbalance in reproductive success[edit | edit source]
Academics such as scholar Angela Nagle and sexologist Kristin Spitznogle, and others such as Roger Devlin argue that imbalance in reproducive success has intensified recently, largely a result of female sexual liberation.
A study which analyzed [GINI coefficients] in number of sexual partners found that, "single men have a higher Gini coefficient (.536) than single women (.470). Thus, female sexual partners are more unequally distributed among single men than male sexual partners are among single women."
A study that analyzed changes in the distribution of sex partners from 2002 to 2011-2013 showed that compared to 2002, top 20% of men (in terms of LMS) now had a 25% increase in sexual partners, and the top 5% of men had an outstanding 38% increase in the number of sexual partners. The study commented that “no significant changes were identified among women in the top 20% and top 5%, overall, and among subgroups”.
References[edit | edit source]
- Brown, G.R., Laland, K.N. and Mulder, M.B. 2009. Bateman's principles and human sex roles. [FullText]
- Janicke, T., et al. 2016. Darwinian sex roles confirmed across the animal kingdom. [Abstract]
- Baumeister, R.F. and Bushman, B., 2010. Social psychology and human nature, brief version. Nelson Education.