A highly variable segment of human subterminal 16p reveals a history of population growth for modern humans outstide Africa

Abstract

We have sequenced a highly polymorphic subterminal noncoding region from human chromosome 16p13.3 flanking the 5' end of the hypervariable minisatellite MS205, in 100 chromosomes sampled from different African and Euroasiatic populations. Coalescence analysis indicates that the time to the most recent common ancestor (approximately 1 million years) predates the appearance of anatomically modern human forms. The root of the network describing this variability lies in Africa. African populations show a greater level of diversity and deeper branches. Most Euroasiatic variability seems to have been generated after a recent out-of-Africa range expansion. A history of population growth is the most likely scenario for the Euroasiatic populations. This pattern of nuclear variability can be reconciled with inferences based on mitochondrial DNA.

Figure 1

Median-joining networks depicting the relationships between the haplotypes for all the populations (a), for only the African populations (b), and for only the non-African populations (c).

Figure 2

Frequency spectra for the populations grouped by continent. The frequency class represents the number of segregating sites for which the mutant form is present in i copies and the ancestral estate in n − i copies, with i ranging from 1 to n − 1 and n being the total number of sequences. As the ancestral state has been inferred, these frequency spectra are unfolded, that is, classes (i, n − i) and (n − i, i) can be distinguished. For convenience, frequency classes from i = 10 to n − 1 have been grouped together. Expected values under neutrality and constant size were obtained by using equation 51 in ref. .

Figure 3

Mismatch distributions for the Eurasian populations. The P value represents the fit to the model of sudden expansion obtained by parametric bootstrap; τ = 2μt (95% confidence interval between parentheses; see Materials and Methods).