1 million people's genes reveal the heritability of the Big Five personality traits — and it's complicated

A family photo album can reflect how physical traits, such as blue eyes or lanky limbs, have been passed down — but a new analysis suggests that the way personality emerges across generations is far more complicated.

The meta-analysis, published Sept.

2 in the journal Nature , is the largest of its kind ever attempted.

The work identified over 1,200 genes linked to five personality traits : extraversion, agreeableness, conscientiousness, openness to experience and neuroticism.

However, the scientists behind the study said its most important conclusion is that no single gene determines whether an individual will have a particular personality trait.

Instead, thousands of genes exert tiny effects that are likely impossible to disentangle from environmental factors that shape our behavior.

Twins and DNA sequencers Researchers have studied the link between genes and behavior for decades.

Before the ability to analyze the genome in detail, many early studies looked to identical twins.

Knowing that identical twins share nearly 100% of their genetic material, scientists compared their traits with those of nonidentical twins and other siblings.

Some studies compared twins raised in the same home with those raised in different homes in an attempt to separate the influence of upbringing from genetics.

These efforts concluded that personality was roughly 50% heritable. ("Heritability" measures how much of the variance seen in a given trait can be explained by genes.) Genetic studies of personality traits previously relied on comparisons between twins.

Now, genetic sequencing technologies have advanced the field. (Image credit: Johner Images via Getty Images) The advent of gene sequencing enabled geneticists to calculate the influence of genes with greater precision than twin studies did.

The most powerful tool in this arsenal is the genome-wide association study (GWAS), which can link traits to gene variants in detail.

These statistical analyses require sample sizes in the millions, though.