A twin study reports BMI correlations: monozygotic twins 0.7, dizygotic twins 0.35. Using the classical twin method (heritability ≈ 2*(rMZ − rDZ)), what is the estimated heritability of BMI and what does that imply about genetic contribution?

• A. Estimated heritability ≈ 140%; which indicates an invalid study because heritability cannot be over 100%
• B. Estimated heritability ≈ 0%, implying genetics play no role and measurement error explains correlations
• C. Estimated heritability ≈ 35%; environmental factors are twice as important as genetics for BMI.
• D. Estimated heritability ≈ 70%; genetics explain a large portion of BMI variation in this sample.

Answer: (D)