[Note: If the effect size is positive it shows a male advantage, if it is negative it shows a female advantage.]
In basically every single society it is found that males desire more sexual partners than females. One large massive study of over 16,000 people across 10 major world regions showed that males were more likely to want more sexual partners than women on both the long-term and short-term. (Schmitt, 2003). The table below is taken from the study, it shows the mean number of sexual partners wanted over an increasingly large period of time.
This method is, of course, not without its flaws. It is difficult to visualize long into the future, but none the less it indicates that males are much more likely to want sexual diversity compared to women and that this is a universal phenomenon, the effect size is about d=0.4 to 0.5.
Let’s look at another line of evidence to see is similar conclusions can be made.
Another piece of evidence which comes to mind is how likely a person is to accept a sexual offer. Time and time again it has been shown that males are greatly more likely to be willing to engage in sexual acts with strangers – this has been shown to be a cross-cultural phenomenon. For example, one study in Hawaii gave 90 women and 27 men a scenario where a student asked for if they wanted to have sex with them, the participants were shown a photograph which was an average formed from a random sample of 40 male and 40 female faces. They observed that, if the person doing the request was interested in a serious relationship, 46.2% of men answered “yes” compared to only 17.5% of women, on the other hand, if the requestor did not suggest a serious relationship 25% of the males answered “yes” and 5% of females did. (Hatfield, Tappé, Bensman & Hayashi, 2013), in another study in Florida requestors of similar attractiveness went up to strangers of the opposite sex (48 males and 48 females) and asked them if they would “go to bed” with them, not a single woman accepted the request whereas 75% of the men did (Clark & Hatfield, 1989). In a similar, but more comprehensive study researchers asked 427 men and 443 women from America, Germany, and Italy whether they would have sex with a stranger at 3 different attractiveness intervals- slightly unattractive, moderately attractive and exceptionally attractive (Schützwohl, Fuchs, McKibbin & Shackelford, 2009). Consistent with other finding males were far more likely to accept the offer at all three stages of attractiveness, with males being over 10 times more likely to accept a request to “go to bed” compared to females overall (d = 1.46).
These results show the same thing that the data from 10 major world regions does. Males are more willing to have more sexual partners.
Large cross-cultural and meta-analyses show that males are more likely compared to females to be willing to engage in casual sex (d=0.74), though this varies across culture and it is likely both biological and social structural influences contribute to sex differences as it varies between nation, have a higher sex drive (d=0.62), which is consistent with a biological model and varies less between nations than willingness to engage in casual sex, (Lippa, 2009) are more permissive of casual sex (d=0.81) and are more likely than females to masturbate (d=0.98). (Oliver & Hyde, 1993)
Now let’s look at the sex differences in mate preferences.
There are large sex differences in what people find important in a partner, which are consistent cross-culturally and cross-generationally and across multiple methods of analysis (such as questionnaires and personal advertisements). (Feingold, 1992)
In a large meta-analysis (Feingold, 1992) of non-physical traits using questionnaires the author found that women rated socioeconomic status (d=-0.69, N=6830), ambitiousness (d=-0.67, N=3174), character (d=-0.35, N=5779), Intelligence (d=-0.3, N=6541), humour (d=-0.14, N=4000) and personality (d=-0.08, N=666) more important than men. And when conducting a meta-analysis on non-physical traits using personal advertisements they also found females showed greater stipulation for character seeking (d=-0.39, N= 2042) and socioeconomic status (d=-0.57, N=3089).
The importance of socioeconomic status can also be seen from dating site data, according to one study which used data from a popular Chinese dating website males with higher incomes are much more likely to get replied to (those with the lowest income of <2000 Chinese Yuan had a probability of being responded to of about 0.05, while those of the highest income of >50000 had a probability of about 0.17), while the effect is way smaller for females (it was almost a constant probability of 0.2 throughout all incomes) (Xia et al. 2014). Similarly a study which measured how much of an effect salary had on perceived attractiveness, surveying people from Europe, China and America, found that “ratings of attractiveness were around 1000 times more sensitive to salary for females rating males,
compared to males rating female.” (Wang et al. 2018)
For physical attractiveness, the pattern is reversed. In another study, which conducted 5 different meta-analyses for 5 research paradigms found that in all 5, males were more likely to value physical attractiveness in a partner compared to females. (Feingold, 1990)
One of the largest data sets on mate preferences is by (Buss, 1989). Which has a total sample of over 10,000 people from 37 different cultures and analyzed 19 mate variables. Out of the 19 mate variables, many had small effect sizes. Some of the ones with largest effect sizes were: Age (ideal age for partner), physical attractiveness (where men placed more weight on attractiveness than females), chastity (more weight for males), good financial prospects (more weight for females) and ambition (more weight for females) (the actual effect sizes are shown in greater detail later). However, looking at these variables individually doesn’t show the full extent of the differences. When these 19 mate variables were used to find Mahalanobis distance (D) the overall effect size for sex differences across all cultures was D = 2.41. This corresponds to an overlap of only 22.8% and means that with only the knowledge of an individual’s mate preferences you can predict their sex with 92.2% accuracy. (Conroy-Beam, Buss, Pham & Shackelford, 2015)
Something which should be noted is the effect of the gender equality of the country. Generally speaking, as the gender equality of a nation increased the sex differences in mate preferences decreased. However, the decrease is dwarfed by the actual sex difference in mate preference, even in a hypothetical country with a perfect gender equality score the overall effect size would still (theoretically) be D = 1.8, which is still considered a very large difference. Research indicates that rather than being an origin of sexual dimorphism in mate preferences, gender equality is just one cause of the sex difference and that the origin is a biological one. (Conroy-Beam, Buss, Pham & Shackelford, 2015).
Below is the theoretical graph created by (Conroy-Beam, Buss, Pham & Shackelford, 2015). It shows how the effect size in mate preferences changes as the gender equality score increases. Figure A shows the predicted sex differences for individual preference dimensions (d) of the 5 “sexually dimorphic” preferences (the preferences which evolutionary theory predicts sex differences in), and figure B shows the overall differences (D) for all the 19 mate preferences, which are the 5 dimorphic preferences and the 14 monomorphic preferences (the other 14 which evolutionary theory does not predict a large sex difference in). The authors do tell readers to caution when interpreting the graphs, they state:
“Although predictions of unobserved data should be interpreted cautiously, this analysis indicates that gender empowerment equality would need to have complex, nonlinear effects on mate preferences—effects not proposed in the extant literature nor observed in our data—to serve as an explanation of observed sexual dimorphism. Combined with evidence that some sex differences increase with increasing gender equality (see Schmitt, 2014, for a review), this suggests that, rather than being an origin of sexual dimorphism in mate preferences, gender equality appears to be just one of many inputs to sexually dimorphic mating adaptations.”