So are those guys afflicted with the XYY genome truly the murderous, insane freaks as portrayed in Alien 3 and popular culture, or do most XYY men have normal lives, never knowing that they’re supposed to be out killing and vandalizing?
I have no cite, but I thought the XYY theory had been disproven. When I read that, I thought about the Alien 3 bit, too.
Yeah, the whole insane murderous XYY thing was blown way out of proportion, at best. They have some physical abnormalities, of course, but there’s no good evidence that they’re more likely to be bad people or anything.
IIRC, the whole thing started with one study that showed that inmates were more likely to be XYY than the general population. But, again IIRC, it turned out to be a poorly done study, with such a small size that the results really aren’t significant.
Here’s a page from a pathologist who things he may have the XYY karyotype: http://www.pathguy.com/xyy.htm
XYY’s on average have more testosterone, are taller, and have slightly lower intelligence test scores than XY’s, but there is considerable overlap between the two grops. The original study that found a much higher rate of incarceration among XYY’s than XY’s was flawed because the sample size was so small. Most recent studies have shown that XYY’s really are more likely to be in prison than XY’s, but not nearly to the same extent as suggested by the original study. At least one study has found that controlling for intelligence, there is no significant difference between XY and XYY incarceration rates. Furthermore, most of the XYY’s in prison are in for property crimes, not violent crimes. It’s important to note that the majority of XYY’s have never been in trouble with the law.
47XYY is pretty much unremarkable to the extent that there isn’t a syndrome associated with it other than being taller and thinner on average than 46XYs. Individuals are usually identified through karyotyping for some other condition, unrelated to 47XYY. It does not affect fertility or cause any observably abnormal developmental problems.
The “47XYY’s are violent” stems primarily from the use of a maximum security prison population as the sample group for the study. Since, as previously noted, 47XYY does not have adverse health affects, it’s difficult to pin down its prevalnce in the general population. Many of the symptoms associated with 47XYY are also diseased that include karyotyping in the course of treatment… i.e. these symptoms lead to their identification as 47XYY… 47XYY doesn’t lead to these symptoms.
This PDF covers it pretty well, and has oodles of references if you want more details.