The study, published in Biological Reviews, reveals that there are differences in male and female sexuality.
Dr Kanazawa, from the London School of Economics and Political Science, explained: “The theory suggests that women may not have sexual orientations in the same sense as men do.
“Rather than being straight or gay, to whom women are sexually attracted may depend largely on the particular partner, their reproductive status, and other circumstances.”
Dr Kanazawa believes that women have had to evolve to deal with the experience of men having more than one partner.
He claimed: “Even though humans have been mildly polygynous throughout evolutionary history, polygynous marriages are often characterized by conflict and tension among co-wives.
“I propose that occasional sex among cowives may have reduced such conflict and tension, and increased their reproductive success.
“Female sexual fluidity may have evolved as an adaptation to facilitate it.”