The approach was male oriented, as was Trivers’ (1972), largely because it was assumed that selection operated more intensely on males than females. It was a case of quantity versus quality: a promiscuous male could leave more descendants, whereas a promiscuous female could leave only better quality offspring. It was assumed that regardless of how many partners a female had, the number of offspring she produced would not change. The second reason for focusing on males was

that male adaptations, whether they were behavioural, anatomical or physiological, were more obvious and more easily studied than female adaptations. There may also have been a cultural bias to focus more on males. When Trivers (1972) reported selleck chemicals llc Bateman’s (1948) ground-breaking work and

used it to develop his theory of sexual selection in PI3K inhibitor the late 1960s and the early 1970s, he presented only part of Bateman’s results, ignoring those that indicated that females might benefit from copulating with multiple partners (see Arnold & Duvall 1994). When, in 2001, I quizzed Trivers about why he had done this, he told me unashamedly that it was pure bias. Trivers (1972) described Bateman’s study in the following terms. Using genetic markers, Bateman (1948) measured the reproductive success of male and female fruitflies Drosophila melanogaster. For a male, the more females he copulated with, the more offspring he fathered (as a result of sperm competition), but for females, reproductive success did not change

after she had copulated with one male regardless of how many other copulation partners she had had. In other words, females needed to copulate only once to fertilize all their eggs, but males benefited from being promiscuous. However, Trivers did not reveal that part way through his experiments, Bateman had been forced to change below the larval growth medium. Like a good scientist, Bateman kept the results separate, and those obtained when food was limiting for the fly larva actually showed that females did benefit, albeit not as much as males, from copulating with more than one partner. Trivers simply ignored those results. Interestingly, it was not until Arnold & Duvall (1994) went back and re-read Bateman’s study that they realized what Trivers had done. Trivers (2002) himself has described how his 1972 paper came about, and more recently, Bateman’s (1948) study has been reappraised (Snyder & Gowaty, 2007). It was not until the 1980s that the idea that females might benefit from promiscuity came back on the agenda. In some ways, it may have been fortunate that Trivers and Parker first focused primarily on males because it meant that behavioural ecologists interested in post-copulatory sexual selection could investigate male function without the additional complexity of female biology.