If one male identical twin is gay, the likelihood that the other is also gay is about 50%. By comparison, the likelihood that a gay male's fraternal twin is also gay is closer to 20%. How might a behavioral geneticist interpret these figures
A)These figures indicate the influence of non-shared environmental factors, thereby suggesting a sizeable genetic contribution to male homosexuality.
B)These figures indicate the influence of non-shared environmental factors, thereby suggesting a sizeable environmental contribution to male homosexuality.
C)These figures indicate heritability, thereby suggesting a sizeable genetic contribution to male homosexuality.
D)These figures indicate heritability, thereby suggesting a sizeable environmental contribution to male homosexuality.

Question

Quizplus · Accepted Answer

The higher concordance rate of homosexuality in identical twins (who share 100% of their genes) compared to fraternal twins (who share about 50% of their genes) suggests a genetic contribution to male homosexuality. This is interpreted as evidence of heritability, where heritability refers to the proportion of variation in a trait among individuals that can be attributed to genetic differences.

If One Male Identical Twin Is Gay, the Likelihood That