sister sister

It’s a question as old as the whole chicken-or-the-egg scenario: Are we a product of our genetics or of our environment? Are we born the way we are, or are we shaped by our experiences? Is it nature or is it nurture? Well kids, that age-old puzzle has been solved. The answer (drum roll, please): It’s both!

According to a study conducted by University of Queensland researcher Beben Benyamin from the Queensland Brain institute, as well as researchers from VU University of Amsterdam, it’s 49% genetics and 51% environmental factors. (So, like, a LITTLE bit more towards nurture, but you gotta take some variance into account.)

How did they come to that conclusion? Twins. Lots and lots of twins. 14.5 million pairs of them, in fact. The researchers looked through thousands of studies conducted between 1952 and 2012 involving twins and compiled the results.

“Twin studies have been conducted for more than 50 years,” Benyamin said, according to The Guardian. “But there is still some debate in terms of how much the variation is due to genetic or environmental factors.”

So yes, they looked at these twin studies! But studies were only used if they incorporated “classical twin design” — that is, comparing non-identical twins (who share half of their genes) to identical twins (who share all of their genes). If a certain trait correlated more closely with non-identical twins than with identical twins, it was more likely environmental. If a certain trait correlated more closely with identical twins than with non-identical twins, it was more likely genetic.

Even though there was a relatively even split between traits / diseases predetermined by genetics and those that develop due to outside circumstances, it’s important to note that certain traits and diseases are much more determined by one or the other. For example (according to this research) bipolar disorder is 68% due to genetics; weight maintenance is 63% due to genetics; eating disorders are 60% environmental. Overall, for physical afflictions and traits, nature were the biggest influence; while nurture influenced values and thoughts.

According to The Guardian, Benyamin says continuing to focus the conversation on nature vs. nurture is missing the point. It should be nature AND nurture. “Both are important sources of variation between individuals,” he said. “. . . Genetics contribute to all traits – the difference is, by how much.”

There you have it, folks — nobody is right, nobody is wrong. But this could totally change the conversation around various issues, including weight gain and mental health, which both have traditionally been thought to be heavily influenced by “nature.” We’re happy this question has finally been answered, but our real excitement lies in the potentially massive impact this could have on research and treatment of various disorders. Once again, go science!

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