Are Murderers Born or Made? - Biological Court Case

Question 1

What are the arguments for nature causing violent murder?

Answer 1

-Evolution = Aggression is naturally selected as suggested by the theory of evolution
-Twin studies = Christianson 1977 twin study showed there was a genetic component to criminality
-Testosterone = DHH, giammanco, dabbs & hargrove, carre, palambo, dolan
-Sertonin and dopamine = virkkuken, seo
-Brain structure = raine, coccaro, li et al, pardini 2014,

Question 2

Arguments for nature BONUS POINT hormones

Answer 2

(BONUS) Hormones i.e dual hormone hypothesis (high testosterone and low cortisol leads to aggression. Those with a disposition to a hormone balance favouring testosterone (to cortisol) will naturally be more aggressive

Question 3

How does natural selection/ evolutionary theory suggest nature is to blame for murder?

Answer 3

The alleles (traits) that are best suited to an ever changing environment will increase their allele frequency within the gene pool over time
Aggression enables an organism to more effectively protect themselves, an offspring or mating partner in a hostile environment (increasing reproductive chances)

Question 4

How does Christianson not work to explain nature as the cause of violence/murder?

Answer 4

35% MZ male and 27% MZ female. These concordance rates are still low despite 100% genetics shared, suggesting social and cultural factors must interact and largely determine criminality (therefore murder)
The increased concordance for MZ could be explained by their closer environmental similarity and they are treated more similarly so identify with each other more

Question 5

How does Christianson 1977 highlight that nature is to blame for murder/violence?

Answer 5

3500 twin pairs in Denmark
Concordance rate of criminality measures for MZ and DZ.twins
MZ twins had a significantly higher concordance rate of criminality suggesting a genetic component to criminality
Male higher than female so also gender component
Suggests your genetics somewhat determine violence and criminal acts

Question 6

Evolutionary theory may not explain murderers being born not made- why?

Answer 6

Evolutionary theory cannot explain cultural differences in aggression:
Differences in aggression levels between cultures is too extreme to be explained by evolutionary theory (more so dictated to by cultural and social norms)
The ifaluk tribe of Ifaluk island has a culture and social norms completely against violence. There is a cultural expectation of low aggression (no rape murder or fights) despite low resources with encourage hostility.

Question 7

How does culture affect if murderers are born or made

Answer 7

Yanomami tribe of the Amazon are known as the fierce people. Up to half of men die violent deaths. It is acceptable to beat and rape women in their structured society.
(Suggests cultural norms completely dictate aggression levels)

Question 8

Draw conclusion for key question: are murderers born or made?

Answer 8

Nurture plays a large role as the environment dictates whether genes for aggression and violence are activated
Even what we think is nature (brain function Raine et al) is often caused by nurture (shaking baby and slapping head, damaging prefrontal cortex)
Although, hormone levels (testosterone and cortisol) vary in people. The ratio of T to C in people may dictate levels of aggression

Question 9

Describe the key question and why we care?

Answer 9

Is aggression the product of genetics or environment?
We care so we can detect potential murderers to ultimately reduce murder rates
And to know how to punish those who commit violent crimes

Question 10

2 arguments for nurture playing a role in murder/violence?

Answer 10

Evolutionary theory can’t explain cultural differences in aggression (Ifaluk vs Yanomami tribe)
Chrisrainson- concordance rate of criminality for MZ twins is already low so there must be social and cultural factors affecting it as they share 100% DNA