In theory, men can have as many children as they want. Of course, the same is not true for women. This major difference in reproductive capabilities indicates wider differences. In this context, that a man is built to have multiple sexual relationships, while a woman is not.
In 1948, A.J. Batemen published his landmark study into mating strategies in nature. His paper "Intrasexual selection in drosophila" revealed that males and females have different reproductive strategies. In turn, these feed into their interactions with the world. Many academics have gone on to confirm his thesis: the biological differences between men and women impact their reproductive strategies. Given humans are built to reproduce, these strategies shape the way that we have sexual relationships; both in initial motivations and seeking alternative mates. In 2010, researchers at the University of Oxford returned to Bateman's ideas for themselves. Their findings confirmed what he had found more than six decades earlier. The group concluded that amongst the 7,000 US adults surveyed," the association between mating and reproductive success was stronger in men so that men with 3 or more consecutive spouses had 19% more children than men with the only spouse. In contrast, spouse number beyond the first partner was not associated with several children in women." Men are naturally predisposed to have multiple sexual partners to maximise their reproductive capabilities.
These studies do not specifically look at cheating. While the results of the Oxford study are interesting, they are also focused on serial monogamy. Their conclusions might have broader implications. However, these test cases make a case for males having multiple partners. That can manifest in many ways. Not just infidelity.
[P1] Biology determines reproductive strategies [P2 Heterosexual male reproductive strategies privilege sexual relationships with multiple women [P3] Cheating is a function of biology
Rejecting the premises
[Rejecting P3] Biological capability does not determine human behaviour