But does that mean that some people are destined to be smart? Twin and family studies often show very strong correlations in the 0.90 range, with identical twins tending to be nearly identical in stature. Perhaps the most striking evidence comes from the rare cases of identical twins reared apart, life’s accidental natural experiment. So, Are Some Destined to Be Smart? Even in identical twins, nature’s closest approximation of a controlled experiment, more than a fifth of the variation in intelligence comes from forces beyond their shared DNA.