Ancient genomes from Iceland reveal the making of a human population.

Opportunities to directly study the founding of a human population and its subsequent evolutionary history are rare. Using genome sequence data from 27 ancient Icelanders, we demonstrate that they are a combination of Norse, Gaelic, and admixed individuals. We further show that these ancient Icelanders are markedly more similar to their source populations in Scandinavia and the British-Irish Isles than to contemporary Icelanders, who have been shaped by 1100 years of extensive genetic drift. Finally, we report evidence of unequal contributions from the ancient founders to the contemporary Icelandic gene pool. These results provide detailed insights into the making of a human population that has proven extraordinarily useful for the discovery of genotype-phenotype associations.

Reconstructing an African haploid genome from the 18th century.

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.

The Y-chromosome point mutation rate in humans.

Mutations are the fundamental source of biological variation, and their rate is a crucial parameter for evolutionary and medical studies. Here we used whole-genome sequence data from 753 Icelandic males, grouped into 274 patrilines, to estimate the point mutation rate for 21.3 Mb of male-specific Y chromosome (MSY) sequence, on the basis of 1,365 meioses (47,123 years). The combined mutation rate for 15.2 Mb of X-degenerate (XDG), X-transposed (XTR) and ampliconic excluding palindromes (rAMP) sequence was 8.71 × 10(-10) mutations per position per year (PPPY). We observed a lower rate (P = 0.04) of 7.37 × 10(-10) PPPY for 6.1 Mb of sequence from palindromes (PAL), which was not statistically different from the rate of 7.2 × 10(-10) PPPY for paternally transmitted autosomes. We postulate that the difference between PAL and the other MSY regions may provide an indication of the rate at which nascent autosomal and PAL de novo mutations are repaired as a result of gene conversion.

Complete mtDNA genomes of Filipino ethnolinguistic groups: a melting pot of recent and ancient lineages in the Asia-Pacific region.

The Philippines is a strategic point in the Asia-Pacific region for the study of human diversity, history and origins, as it is a cross-road for human migrations and consequently exhibits enormous ethnolinguistic diversity. Following on a previous in-depth study of Y-chromosome variation, here we provide new insights into the maternal genetic history of Filipino ethnolinguistic groups by surveying complete mitochondrial DNA (mtDNA) genomes from a total of 14 groups (11 groups in this study and 3 groups previously published) including previously published mtDNA hypervariable segment (HVS) data from Filipino regional center groups. Comparison of HVS data indicate genetic differences between ethnolinguistic and regional center groups. The complete mtDNA genomes of 14 ethnolinguistic groups reveal genetic aspects consistent with the Y-chromosome, namely: diversity and heterogeneity of groups, no support for a simple dichotomy between Negrito and non-Negrito groups, and different genetic affinities with Asia-Pacific groups that are both ancient and recent. Although some mtDNA haplogroups can be associated with the Austronesian expansion, there are others that associate with South Asia, Near Oceania and Australia that are consistent with a southern migration route for ethnolinguistic group ancestors into the Asia-Pacific, with a timeline that overlaps with the initial colonization of the Asia-Pacific region, the initial colonization of the Philippines and a possible separate post-colonization migration into the Philippine archipelago.

High-throughput sequencing of complete human mtDNA genomes from the Philippines.

Because of the time and cost associated with Sanger sequencing of complete human mtDNA genomes, practically all evolutionary studies have screened samples first to define haplogroups and then either selected a few samples from each haplogroup, or many samples from a particular haplogroup of interest, for complete mtDNA genome sequencing. Such biased sampling precludes many analyses of interest. Here, we used high-throughput sequencing platforms to generate, rapidly and inexpensively, 109 complete mtDNA genome sequences from random samples of individuals from three Filipino groups, including one Negrito group, the Mamanwa. We obtained on average ∼55-fold coverage per sequence, with <1% missing data per sequence. Various analyses attest to the accuracy of the sequences, including comparison to sequences of the first hypervariable segment of the control region generated by Sanger sequencing; patterns of nucleotide substitution and the distribution of polymorphic sites across the genome; and the observed haplogroups. Bayesian skyline plots of population size change through time indicate similar patterns for all three Filipino groups, but sharply contrast with such plots previously constructed from biased sampling of complete mtDNA genomes, as well as with an artificially constructed sample of sequences that mimics the biased sampling. Our results clearly demonstrate that the high-throughput sequencing platforms are the methodology of choice for generating complete mtDNA genome sequences.