The idea that men pursue more sexual partners than women and are more promiscuous is a theory which must be dismissed. Data is finally coming in.

History of a sexist idea

The sexist theory of sexually aggressive males and “hard to get” females was put forward by botanist Angus Bateman in 1948, a scientist who never even published about this.  He set up a series of breeding experiments on fruit flies with different mutations as markers. He put equal numbers of males and females together in lab flasks, letting them mate for several days. Then he counted their offspring, using the inherited mutations to calculate how many individuals each fly had mated with.   Bateman concluded that male reproductive success increases linearly with the number of mates and that female reproductive success peaks after mating with only one male. And he also concluded that this is universal for animals.

In 1972 another scientist, Robert Trivers, argued that sperms are a cheap investment so that males evolved to abandon their mate and promiscuously pursue females to mate with. He said that female investment in eggs is comparatively high so that females mate with only one make and care for young. This theory fit with the sexist ideas of the times, where women were hard to get and men worked hard to get to “third base”.

Smash the sexism

In reality, it makes little sense to compare the cost of one egg to one sperm. A male produces hundreds of millions of sperms to fertilize just one egg. The relevant comparison is the cost of millions of sperm versus that of one egg. Also, semen contains expensive nutrients and chemicals. We wouldn’t expect to see “sperm depletion” if having sex with as many females as possible was true.  Nor “refractory periods” when a man cannot repeat sex and ejaculation until a period of recovery has occurred.

Research with birds shows that most which were thought to be monogamous actually have babies with multiple partners. Behavioural ecologist Tim Birkhead concluded in 2000  that generations of  biologists assumed females to be preferentially sexually monogamous, but it is now clear that this is wrong. If better observations and studies would have disproved this promiscuous male – hard-to-get female myth, why did scientists conclude the opposite.  Perhaps this is a case of society’s values creating the idea, and scientists simply assuming their unquestioned assumptions that “good girls” were not sexual, not interested in sex, and that men were sexually interested and aggressive.  The scientists saw what they expected to see, and Bateman’s research was never replicated. And if a female will bite the head off a male and eat it, males are the hard to get ones.

References

Ejaculate Cost and Male Choice Donald A. Dewsbury  The American Naturalist, May 1982

Promiscuity: An Evolutionary History of Sperm Competition Tim Birkhead Harvard University, 2000

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