[Poohbah]

Isn't the "XYY" genome somewhat questionable? I seem to recall reading that the evidence is thin (and some would say anorexic), with a lot of controversy surrounding the interpretation of the evidence.

[Myrddin]

Extracting and karyotyping XYY is pretty straight forward. The X0 Turner's syndrome (female) is similarly determined. XXY is Klinefelter's syndrome. It is mechanical observation. The presence of the genotypic expression as observed via the karyotype is not a guarantee of phenotypic expression. A phenotypic expression confirmed by examination of the karyotype would be unsurprising.

A description of typical XYY supermales gleaned from another web page:

• On the average, these guys are taller have worse acne, have higher average hFSH, hLH, and testosterone (this has held up nicely), and allegedly average slightly lower IQ's (this point's very questionable), than XY's. These men average substantially higher testosterone levels, and are slightly over-represented in prison populations;
• among tall men of any karyotype, the rate of conviction, especially for violent crimes, correlates surprisingly well with plasma testosterone levels, results of psychological tests correlate poorly with all these variables;
• the typical XYY's crime is wife-beating;
• the differences between XYY's and their XY counterparts are anything but striking.