Or (Heterosexual) Male privilege, not evolution or innate female frigidness, explains the gender difference in accepting random propositions for casual sex.
[M]ost of the gender difference in women’s and men’s propensity to agree to a broad-daylight, out-of-nowhere proposition for casual sex is driven by women’s perception that their risks are higher, and their likely enjoyment is lower from the proposer.
In the actual paper, Conley (2011) concludes:
First, male sexual proposers (who approached women) are uniformly seen as less desirable than female sexual proposers (who approached men). Therefore, gender differences in the original Clark and Hatfield study are due more to the gender of the proposer than to the gender of the study participants. Moreover, the idea that these gender differences reflect broad, evolved differences in women’s and men’s mating strategies was not supported. Across studies involving both actual and hypothetical sexual encounters, the only consistently significant predictor of acceptance of the sexual proposal, both for women and for men, was the perception that the proposer is sexually capable (i.e., would be “good in bed”). The perceptions of sexual capabilities also mediated the relationship between gender and acceptance of casual sex offers. Finally, indirect evidence suggests that perceptions of risk may play a role in gender differences in casual sex attitudes.