By Jesse Bering
(Scientific American) In a now-classic, pre-Internet-porn study (PDF) by British evolutionary biologists Robin Baker and Mark Bellis, male university students were found to masturbate to ejaculation about every 72 hours, and “on the majority of occasions, their last masturbation is within 48 hours of their next in-pair copulation.” If they’re not having intercourse every day, that is to say, men tend to pleasure themselves to completion no more than two days prior to having actual sex.
Baker and Bellis’s quite logical argument for this seemingly counterintuitive state of affairs (after all, shouldn’t men try to stock up as much sperm as possible in their testes rather than spill their seeds so wastefully in a rather infertile swath of toilet paper or a dirty sock?) is that because there is a “shelf-life” for sperm cells – they remain viable for only 5-7 days after production – and because adult human males manufacture a whopping 3 million sperm per day, masturbation is an evolved strategy for shedding old sperm while making room for new, fitter sperm. It’s quality over quantity.
Read the rest http://www.scientificamerican.com/blog/post.cfm?id=one-reason-why-humans-are-special-a-2010-06-22
