The Origins of the Incest Taboo Are Unclear,even After Decades

The origins of the incest taboo are unclear,even after decades of careful study.One theory holds that the taboo exists as a result of the fear of biological degeneration and the possible effects of inbreeding.One of the arguments against this theory is that

A) data from careful population sampling clearly shows this does not happen.
B) the human genome project has shown that reproduction in affinal groups does not result in genetic damage.
C) both genetics and population science emerged long after the incest taboo.
D) early researchers of the incest taboo did not fully investigate the phenomenon in fieldwork.