newish possible explanation for why women menstruate

[Felan]

Interesting post on Pharyngula on newish possible explanation for why women menstruate.

http://scienceblogs.com/pharyngula/2011/12/why_do_women_menstruate.php

 

[Cogwulf]

I've always thought that it was the cost of not going through heat and being able to conceive at any time of the year. I don't know how well that would correlate with facts though.

 

[Vrecknidj]

The proposed answer looks entirely plausible. It's a well-reasoned reply.