Did you know individual life events rarely change core traits?

A legal precedent set in 2009 saw a defence lawyer in Trieste, Italy, successfully argue for a reduced murder sentence. He claimed his client possessed the 'warrior gene', a variant of the MAOA gene linked to aggressive behaviour.

While the court granted a one-year reduction, the underlying science has since faced significant scrutiny.

The collapse of single-gene theories

Researchers initially established a connection between the MAOA gene variant and violent behaviour during the 1990s.

However, Professor Aysu Okbay of Amsterdam UMC notes that the premise of single-gene explanations has collapsed.

"People believed that behaviours result from a few genes which have major impacts," she states. "The entire concept has been proven to be incorrect."

Current research suggests personality develops through thousands of genetic variants, each producing imperceptible effects. A 2015 meta-analysis of 2,500 twin studies found:

• Genetic differences account for roughly 47% of personality variation.
• The Big Five traits show only 9 to 18% heritability in genome-wide studies.
• Humans possess less genetic potential than originally believed.

Environmental impacts on character

Professor Brent Roberts from the University of Illinois at Urbana-Champaign observes that major life events often have a limited impact on core identity.

He explains that major adult traumatic events create only mild psychological effects, which will not result in significant long-term consequences.

According to his research, people experience no significant personality changes from:

• Marriage
• Divorce
• Financial windfalls

These events function as individual elements that rarely alter the fundamental traits defining a human being.