By examining paternal (Y) and maternal (mtDNA) lineages over human history, we can observe striking inequalities. The figures (derived from David Reich’s 2018 book on ancient DNA) below help illustrate how a small number of men have contributed in an outsized way to certain modern lineages.

David Reich on these “star clusters:”

The male-lineage Y chromosome types carried by these groups were absent in India and Europe before the Bronze age, but are predominant in both places today, Reich says. Much of this ancestry is the result of what is known as a “star cluster,” when the genes of one very powerful man appear in millions of descendants. Reich estimates that 20 to 40 percent of Indian men and 30 to 50 percent of Eastern European men descend from a single man who lived between 6,800 and 4,800 years ago. In Iberia, Reich’s team uncovered further evidence of sex bias. By 4,000 years ago, genes spread by the descendants of the steppe people accounted for about 40 percent of the ancestry of those populations, with about 60 percent coming from the local inhabitants who had lived there previously. “But if you look at the Y chromosomes—the DNA that people get from their fathers—it was more or less 100 percent from the steppe.”

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