What Do Twin Studies Tell Us?

Studying differences between identical twins separated at birth has long been a way for scientists to study the impact genes have on our bodies, attitudes, and decisions.

But are they any good?

According to this article in Slate, the answer is no.

Twin studies rest on two fundamental assumptions: 1) Monozygotic twins are genetically identical, and 2) the world treats monozygotic and dizygotic twins equivalently (the so-called “equal environments assumption”). The first is demonstrably and absolutely untrue, while the second has never been proven.

The article goes gives a brief but interesting history of twin studies, and some curious findings from twin studies in the last two decades. The highlights:

• We have less free will than we thought
• Almost half of our political ideologies are genetically based
• One quarter of our financial decisions can be predicted by our genotypes.

Of course, that’s assuming you believe in these sorts of studies…..

A good counter-argument is given at Gene Expression.