Its so easy, even a caveman can do it.

Melissa McEwen recently wrote an interesting blog post about sex in today's hunter-gatherer tribes. You might want to read it and the study she's talking about. Masturbation in these two tribes was unheard of, which was a pretty surprising piece of information for me at least.

I'd say the sex was good enough for Mankind to survive and thrive. :)

Thats crazy because many primates masturbate. In my opinion you had sex as much as your options let you. Im sure there was jockeying for most attractive and young able to breed females. I find it apparent that females have generally selected for two attributes.

1) "winners" of physical contests 2) selection of some type and larger genitalia in males.

I make the first assumption purely based on the fact that men have testosterone levels much higher than women which effectively shorten a males lifespan and make him more susceptible to disease.

The second assumption is the fact that compared to all living primates, humans have the largest penises, even when accounting for a difference in body size. Not to mention much larger testes indicate a track record of polygamy, giving the male the ability to copulate and ejaculate many times in a day.

"One characteristic among primates has been clearly targeted for possible selection by Fisherian female choice--male penis size. Primate males living in groups with many females and many males, groups in which promiscuity is the mating rule, have long penes (Dixon 1978). Male chimps, in fact, use their penis for display toward estrous females. Because a longer penis would give a female pleasure (note that the human male has the longest and thickest penis of any primate), female choice might have been a factor driving penis length to extremes among primates." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 109)