Three...that's the magic number

I've got Biddulph's Raising Boys where he talks about it, but I've also come across the theory in books by Matt Ridley (http://www.mattridley.co.uk/) (originally a zoologist!) and Simon Baron-Cohen (http://www.autismresearchcentre.com/arc/staff_member.asp?id=33). Follow the link on 'Testosterone and Autism' on his page there for an indication of his line of enquiry.

I give the theory credence, since there have been rumblings about a link long before Biddulph; Baron-Cohen's very well respected here.