Alan is an adopted child who lives with three siblings, all biological children of his adoptive parents. Alan's math skills are far better than those of his adoptive parents or his adoptive siblings. This provides evidence that

shared familial influences play a far bigger role than was previously believed.
genes may have a stronger effect than familial environment on some abilities.
much less of the environmental effects on personality come from outside the
family than was previously believed.
Alan's own initiative to excel is greater than that of his adoptive family

genes may have a stronger effect than familial environment on some abilities.