Monogamy easier for women?

I have talked to people who believe that men aren’t “designed” to be faithful.  They point to biology and the desire to spread seeds or something.  What baffles me is when they say women manage mongamgy so much easier.  I am not clear on what evidence they have for this.  Why do some believe that women can be faithful with such ease?

People cheat for different reasons and I think women are just as tempted as men are.  We all have the same ability to make choices that avoid infidelity.  Maybe men get bored with the same partner but women do too.

Do you think it is easier for women to stay faithful?  How do you handle temptation?