Hey Peter! Twin studies are one of the more powerful tools we have to try and separate out the effects of genetics, shared environment and non shared environmen

Hey Peter! Twin studies are one of the more powerful tools we have to try and separate out the effects of genetics, shared environment and non shared environment in humans. Shared environment represents what twins raised in the same household have in common in their environment and non shared environment what is still different. Studies of heritability tend to indicate for many traits that genetics have the largest role and (perhaps surprisingly) non shared environment the next largest with shared environment having the smallest (though often still important) role to play. Your example of the twins would be a classic case of non shared environmental influence. Certainly nobody claims that environmental influences are not important and like most things the details are complicated and leave much room for debate over the exact role of each component in determining traits. In some ways it is true that the environmental factors are the most interesting since they are the ones we have most control or at least influence over for ourselves and our children.