Species of various animals are selectively bred to produce aggressive individuals
Ability to select most aggressive dogs and breeding them together gives a new generation with same aggressive tendancies that are specific genes that determine levels of aggression
Humans have evidence for geneticcomponent to aggression from twin studies and adoption studies where criminality used to measure aggression
Christiansen - twin aggression study - Method
Analysis of 3586 pairs of twins born between 1881 and 1910 in Denmark
Find concordance rates
926 Ps were registered for criminality
MZ and DZ twins compared
Christiansen - twin aggression study - findings
Twins of criminals more likely to be criminals
Geneticcomponent to aggression
Christiansen - twin aggression study -Conclusion
Male MZ twins had 35%concordance rate for criminality
12% in DZ male twins
Female MZ twins show 21% concordance 8% concordance
Christiansen - twin aggression study -Evaluation
Genetics can't be the only factor
MZ concordance wasn't 100%
Studying all twins in time frame gives different concordance rates
Environment might account for different concordance rates
