Border and his colleagues are not the first to raise the possibility of spurious genetic correlations. When designing studies, geneticists can control for the effects of factors like parental traits and childhood environment by comparing people who have those things in common—that is, siblings. Earlier this year, statistical geneticist Laurence Howe and a team of researchers did just that. When Howe compared siblings with each other, he observed no genetic correlation between BMI and years of education. Somehow, it was parents, and not genes themselves, that had made weight and education seem genetically connected.
But Howe’s study didn’t explain exactly how parents played a role. There were some promising possibilities. Parents don’t just pass down genes
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