Men and women have different regrets after sex.

A new study says men usually regret not having sex with more people while women regret having sex with the wrong person.

Researchers at UCLA and the University of Texas say this feeling of regret is a part of the evolutionary process: Our male ancestors thought every missed opportunity to have sex with a new partner was a missed opportunity to reproduce, while our female ancestors regretted hooking up with a bad mate.

The study also showed that more women than men regretted having sex with a physically unattractive partner.

--Rob Archer