Silverback female gorillas use sex as a tactic to thwart their rivals with even pregnant apes courting their male to stop other females conceiving. Diane Doran-Sheehy at Stony Brook University in New York says this kind of competitive behaviour may even help explain how humans evolved into a mostly monogamous species.
However, there has been a number of highly publicised research that suggests the human females are not as monogamous we like to think they are. Proof enough if you do a Google search for ‘cheating wives’ or ‘female infidelity’. Maybe women have more in common with the cheating chimps – http://news.bbc.co.uk/1/hi/scotland/edinburgh_and_east/7463088.stm.
Apparently 1 in 5 women admit to cheating but I suspect this figure is much higher. Women have much more to lose by admitting infidelity than men and so many I think would keep their cheating ways to themselves and the lucky chap at the company Christmas party 
