Editing Exogamy (section)

== Biology of exogamy ==
Exogamy often results in two individuals that are not closely genetically related marrying each other; that is, [[outbreeding]] as opposed to [[inbreeding]]. This may benefit offspring as it reduces the risk of the offspring inheriting two copies of a defective gene. Nancy Wilmsen Thornhill states that the drive in humans to not reproduce or be attracted to one's immediate family is evolutionarily adaptive, as it reduces the risk of children having genetic defects caused by inbreeding, as a result of inheriting two copies of a deleterious recessive gene.<ref>{{cite book |vauthors=Thornhill N |date=1993 |title=The Natural History of Inbreeding and Outbreeding: Theoretical and Empirical Perspectives. |publisher=The University of Chicago Press |location=Chicago}}</ref>

In one [[Amish|Old Order Amish]] society, inbreeding increases the risk of "neonatal and postneonatal mortality."<ref>{{cite journal | vauthors = Dorsten LE, Hotchkiss L, King TM | title = The effect of inbreeding on early childhood mortality: twelve generations of an Amish settlement | journal = Demography | volume = 36 | issue = 2 | pages = 263–71 | date = May 1999 | pmid = 10332616 | doi = 10.2307/2648113 | s2cid = 26311145 | jstor = 2648113 | doi-access = free }}</ref> In French populations, the children of first cousins develop [[cystinosis]] at a greater rate than the general population.<ref>{{cite journal | vauthors = Tchen P, Bois E, Feingold J, Feingold N, Kaplan J | title = Inbreeding in recessive diseases | journal = Human Genetics | volume = 38 | issue = 2 | pages = 163–7 | date = September 1977 | pmid = 302820 | doi = 10.1007/BF00527398 | s2cid = 8849012 }}</ref>