Editing Human sexual activity (section)

===Avoidance of inbreeding===
Although the main adaptive function of human sexual activity is reproduction, human sexual activity also includes the adaptive constraint of avoiding close [[inbreeding]], since inbreeding can have deleterious effects on progeny.  Charles Darwin, who was married to his first cousin Emma Wedgwood, considered that the ill health that plagued his family was a consequence of inbreeding.<ref>Berra, T.M., Alvarez, G., Ceballos, F.C. (2010) Was the Darwin/Wedgwood Dynasty Adversely Affected by Consanguinity? Bioscience 60:376-383. ISSN 0006-3568.`electronic ISSN 1525-3244</ref> In general, inbreeding between individuals who are closely genetically related leads to the expression of deleterious recessive [[mutation]]s.  The avoidance of inbreeding as a constraint on human sexual activity is apparent in the near universal cultural [[sexual inhibition|inhibitions]] in human societies of sexual activity between closely related individuals.<ref>Degler, C.N. (1991). In Search of Human Nature. Chapter 10, New York: Oxford University Press</ref> Human [[outcrossing]] sexual activity provides the adaptive benefit of the masking of expression of deleterious recessive mutations.<ref>Bernstein H, Byerly HC, Hopf FA, Michod RE. Genetic damage, mutation, and the evolution of sex. Science. 1985 Sep 20;229(4719):1277-81. doi: 10.1126/science.3898363. PMID 3898363</ref>