Much of the redpill's foundation and theory is founded on evolutionary psychology. The general idea is that women have sex in exchange for commitment, while men are naturally promiscuous. However more recent research in particular the book Sex at Dawn argues with this idea saying that early on in society we had more egalitarian gender roles. There, men and women both had multiple partners, that paternity was shared.

Quick Summary of points

-Men's penis's are designed in a way to pump out other men's semen in women. (We also have largest penors for primates in relation to body size)

-Men's sperm are designed to fight and block off foreign sperm in vaginas. Sperm are actually designed to fight off another man's sperm. Most sperm are blockers and killers only 1-2% actually are the ones that go to fertilize the egg.

-Women's orgasms take much longer time to climax than a Man's. The way this happens is when a woman fucks multiple men at once. She transfers 'being turned on' from one guy to another.

-Then at the end of it all the sperm fight for the egg.

-Healthy motile sperm goes hand in hand with being a virile (Alpha male)

Sources

http://en.wikipedia.org/wiki/Sex_at_Dawn

http://translate.googleusercontent.com/translate_c?depth=1&hl=de&ie=UTF8&prev=_t&rurl=translate.google.com&sl=de&tl=en&u=http://www.nytimes.com/2013/06/16/books/review/what-do-women-want-by-daniel-bergner.html%3Fpagewanted%3D1%26_r%3D0&usg=ALkJrhivrkxSzsZL8ESrTVG34YcipfqPoA

http://jasonstotts.com/2013/04/on-polysexuality-revised/

Conclusion

This is not to say that previous science was wrong. We aren't purely promiscuous like other animals but we also do like long term partners as well. And it's not to say that in the years when we did become a sedentary society that monogamy started to become a part of our psychology as well. Jealous and anger is still a natural response to infidelity.

However, what I do want to challenge here is that a lot of the guys think that its unnatural for a woman to enjoy casual sex. There was a study here that showed if you removed the chances of being shamed + the sexual skill of the man, most women will be up for it. Women don't just naturally gravitate to the most alpha dude, because he has the best genes. Women and men are designed so women have sex with multiple guys, and the best sperm wins.

Monogamy isn't natural for men or for women.