If you’re in a long-term relationship, you’ve probably entertained the idea of cheating on your significant other. Those dirty and dishonest thoughts that stream through your imagination may fill you with guilt, but there’s a growing body of evidence that point to biology and evolution as the culprits in the game of love. Males with roving eyes and an incessant urge to procreate could find reproductive success in multiple partners. On the other hand, females who take on multiple male partners are in fact subscribing to an insurance policy of sorts: If her main partner dies, her offspring will be taken care of, and at the same she is enriching the gene pool. Anthropologist Helen Fisher has proposed these theories, backed up by scientific evidence, and written extensively on the matter. Most of the ideas in this article are hers. So now you know, when you get caught cheating, you can always blame evolution. Here are 9 eye-opening facts about infidelity.