Jacobs

• Claims

  • genetic theory, XYY Theory
  • males born with an extra Y chromosome are more aggressive
  • nicknamed supermales
• Components

  • correlation study
  • compared men in prison to men in the general public
  • 1/1000 in the general public were XYY
  • 15/1000 in the prison population were XYY
• Credibility

  • scientific
  • peer reviewed study
  • any male can be tested for the abnormality
  • deterministic
  • reductionist
• Application

  • Richard Speck: mass murderer, was said to have the abnormality but it was a mistest
  • John Wayne Gacy: serial killer suspected of having the abnormality but was never tested
• Refuting Evidence

  • ignores environmental factors for criminality
  • Theilgaard 1984: repeated the study but found no links
• Supporting Evidence

  • Y chromosome = testosterone levels = levels of aggression
  • XYY linked to low intelligence, which links to petty crime
  • Er Cole Rao 1997: found an extra X chromosome in women, supporting the idea of additional chromosomes