Thank you, Agmo & Ellingsen

Over the years I have heard the data repeated many times.  Based on a surveys men have more lifetime heterosexual sex partners than women.  For the United States it is reported as 12:3, for Norway 13:5 and for Britain 10:3.

Whenever this data is quote we are reminded that man are meant to want to spread their 'genome' as widely as possible, females are meant to try and bond a longer-term partner to get them to help raise the kids.

The only problem is that this data doesn't make sense.  As Agmo & Ellingsen (2003) writes "Under the condition that the population consists of 50% of each sex..." (which they established is largely the case) "...the number of partners must inevitably be exactly the same for men and women."

So we don't need 'just so' theories about why men have more sex (with women) than women have (with men)--because that flat out cannot have happened.

Of course there are lots of theories to be made about how they misremember, differently categorise and flat out lie about it... but that's a whole 'nother thing.