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A genome is a mosaic of chromosome fragments from ancestors who existed some arbitrary number of generations earlier. Here, we reconstruct the genome of Hans Jonatan (HJ), born in the Caribbean in 1784 to an enslaved African mother and European father. HJ migrated to Iceland in 1802, married and had two children. We genotyped 182 of his 788 descendants using single-nucleotide polymorphism (SNP) chips and whole-genome sequenced (WGS) 20 of them. Using these data, we reconstructed 38% of HJ's maternal genome and inferred that his mother was from the region spanned by Benin, Nigeria and Cameroon.

Motivation We introduce HaploGrouper, a versatile software to classify haplotypes into haplogroups on the basis of a known phylogenetic tree. A typical use case for this software is the assignment of haplogroups to human mitochondrial DNA (mtDNA) or Y-chromosome haplotypes. Existing state-of-the-art haplogroup-calling software is typically hard-wired to work only with either mtDNA or Y-chromosome haplotypes from humans. Results HaploGrouper exhibits comparable accuracy in these instances and has the advantage of being able to assign haplogroups to any kind of haplotypes from any species—given an extant annotated phylogenetic tree defined by sequence variants. Availability and implementation The software is available at the following URL https://gitlab.com/bio_anth_decode/haploGrouper. Supplementary information Supplementary data are available at Bioinformatics online.

Founder effects in modern populations The genomes of ancient humans can reveal patterns of early human migration (see the Perspective by Achilli et al. ). Iceland has a genetically distinct population, despite relatively recent settlement (∼1100 years ago). Ebenesersdóttir et al. examined the genomes of ancient Icelandic people, dating to near the colonization of Iceland, and compared them with modernday Icelandic populations. The ancient DNA revealed that the founders had Gaelic and Norse origins. Genetic drift since the initial settlement has left modern Icelanders with allele frequencies that are distinctive, although still skewed toward those of their Norse founders. Scheib et al. sequenced ancient genomes from the Channel Islands of California, USA, and Ontario, Canada. The ancient Ontario population was similar to other ancient North Americans, as well as to modern Algonquian-speaking Native Americans. In contrast, the California individuals were more like groups that now live in Mexico and South America. It appears that a genetic split and population isolation likely occurred during the Ice Age, but the peoples remixed at a later date. Science , this issue p. 1028 , p. 1024 ; see also p. 964