At one time, it was thought that men with the XYY
karyotype were more prone to violence, aberrent behavior, and
criminal activity. There was even a study published that claimed that
XYY men were 25-60 times more likely to perform
criminal acts, and
Richard Speck actually tried to use (falsely) the XYY karyotype as an
excuse for committing 8
murders.
Another study claimed that more prison inmates were XYY than were XY.
It was later found, after a random sampling among the civilian population, that the prison population fairly closely mimicked the general population.**
And, being
the Devil's Advocate that I am, I'd like to see some proof comparing the heights, acne problems, and behaviours of XYY men to their normal brothers. It seems to me that at least some of these cases presented may actually be exceptions to the norm, and that many men may be XYY and not even know it.
Or, maybe I'm too difficult to convince.
** - The best source I can find for anything related to this is Beckwith & King, New Scientist, 1974, pp. 474-76, but I could only get access to the abstract thus far.