Children of consanguineous unions carry long runs of homozygosity (ROH) in their genomes, due to their parents’ recent shared ancestry. This increases the burden of recessive disease in populations with high levels of consanguinity and has been heavily studied in some groups. However, there has been little investigation of the broader effect of consanguinity on patterns of genetic variation on a global scale. Here, we collect published genetic data and information about marriage practice from 395 worldwide populations and show that reported preference for cousin marriage has a detectable association with the distribution of long ROH in this sample, increasing the expected number of ROH longer than 10cM by a factor of 2.2. Variation in marriage practice and consequent rates of consanguinity is therefore an important aspect of demographic history for the purposes of modeling human genetic variation. However, reported marriage practices explain a relatively small proportion of the variation in ROH distribution and consequently, population genetic data are only partially informative about cultural preferences.
Sahoo, Samali Anova; Zaidi, Arslan A.; Anagol, Santosh; and Mathieson, Iain, "Long Runs of Homozygosity Are Correlated with Marriage Preferences across Global Population Samples" (2022). Human Biology Open Access Pre-Prints. 197.