The Origins of the Incest Taboo Are Unclear, Even After

The origins of the incest taboo are unclear, even after decades of careful study. One theory holds that the taboo is due to a fear of creating genetic defects in offspring. What is one argument against this theory?

A) If a harmful trait runs in a family, systematic inbreeding will increase the possibility of the defective gene being passed along.
B) Surveys show that most people do not believe that incest leads to genetic defects.
C) Incest taboos predate any scientific understanding of human genetics, so this could not be the cause.
D) The human genome project has shown that incest does not result in genetic damage.