On the Number of Ancestors to a DNA Sequence

If homologous sequences in a population are not subject to recombination, they can all be traced back to one ancestral sequence. However, the rest of our genome is subject to recombination and will be spread out on a series of individuals. The distribution of ancestral material to an extant chromosome is here investigated by the coalescent with recombination, and the results are discussed relative to humans. In an ancestral population of actual size 1.3 million a minority of <6.4% will carry material ancestral to any present human. The estimated actual population size can be even higher, 5 million, reducing the percentage to 1.7%.