The availability of cost-effective, high throughput technologies to genotype common alleles has yielded an unprecedented wealth of genomewide data on human variation, deeply sampled within and across populations. We have developed a rapid method that facilitates extensive evaluation of shared genetic segments across millions of sample-pairs.We report analysis of such sharing to improve understanding of recent genetic history of samples, both genomewide as well as for specific loci. We show extensive hidden relatedness between individuals within populations that provides estimates of demographic parameters. Specifically, for Ashkenazi Jewish populations we demonstrate and a severe bottleneck 20-25 generations before present. We show genetic sharing to be focused at regions that suggest a causal mechanism for ancient sharing rather than recent relatedness, such as the HLA and the commonly polymorphic inversion of 5Mbp on chromosome 8p23.1 . Finally, we filter out sharing that is non-informative because it is too recent or causal and show clustering of populations based on genetic sharing.

Whole population, genome-wide mapping of hidden relatedness. Gusev A, Lowe JK, Stoffel M, Daly MJ, Altshuler D, Breslow JL, Friedman JM, Pe'er I. Genome Res. 2009 Feb;19(2):318-26. Epub 2008 Oct 29. PMID: 18971310