Genetic structure and sex-biased gene flow in the history of southern African populations.

OBJECTIVES: We investigated the genetic history of southern African populations with a special focus on their paternal history. We reexamined previous claims that the Y-chromosome haplogroup E1b1b (E-M293) was brought to southern Africa by pastoralists from eastern Africa, and investigated patterns of sex-biased gene flow in southern Africa. MATERIALS AND METHODS: We analyzed previously published complete mtDNA genome sequences and ∼900 kb of NRY sequences from 23 populations from Namibia, Botswana, and Zambia, as well as haplogroup frequencies from a large sample of southern African populations and 23 newly genotyped Y-linked STR loci for samples assigned to haplogroup E1b1b. RESULTS: Our results support an eastern African origin for Y-chromosome haplogroup E1b1b (E-M293); however, its current distribution in southern Africa is not strongly associated with pastoralism, suggesting more complex demographic events and/or changes in subsistence practices in this region. The Bantu expansion in southern Africa had a notable genetic impact and was probably a rapid, male-dominated expansion. Our finding of a significant increase in the intensity of the sex-biased gene flow from north to south may reflect changes in the social dynamics between Khoisan and Bantu groups over time. CONCLUSIONS: Our study shows that the population history of southern Africa has been complex, with different immigrating groups mixing to different degrees with the autochthonous populations. The Bantu expansion led to heavily sex-biased admixture as a result of interactions between Khoisan females and Bantu males, with a geographic gradient which may reflect changes in the social dynamics between Khoisan and Bantu groups over time.

Can Superselective Intra-Arterial Chemoradiotherapy Replace Surgery Followed by Radiation for Advanced Cancer of the Tongue and Floor of the Mouth?

PURPOSE: The purpose of this study was to compare quality of life (QoL) and the survival rate after surgery with and without radiotherapy versus superselective intra-arterial chemoradiotherapy (SSIACRT) for advanced cancer of the tongue and floor of the mouth. MATERIALS AND METHODS: Patients with stage III and IV squamous cell carcinoma of the tongue and floor of the mouth treated between 2000 and 2013 were included in this study. The predictor variables were surgery without radiotherapy, surgery followed by radiotherapy, and SSIACRT. The outcome variables were QoL and the survival rate. The University of Washington QoL questionnaire (UW-QOL) was used for evaluation of QoL. The Kaplan-Meier method was used to estimate the overall survival rate. The UW-QOL was analyzed by analysis of covariance, and the survival rate was analyzed statistically by the log-rank test. RESULTS: Sixty-two patients were eligible for this study. Of these, 13 were treated by surgery without radiotherapy, 29 were treated by surgery plus radiotherapy, and 20 were treated by SSIACRT. The SSIACRT group had the best UW-QOL scores among the 3 groups. The 5-year Kaplan-Meier disease-specific survival rates for these groups were 92.9%, 62.9%, and 83.2%, respectively, with no significant difference (P = .20) shown. CONCLUSIONS: The QoL scores of the SSIACRT group were the best among the 3 groups in most domains. The superiority of QoL and the survival rate in the SSIACRT group showed that SSIACRT should be preferred in managing advanced cancer of the tongue and floor of the mouth.

Unraveling the complex maternal history of Southern African Khoisan populations.

The Khoisan populations of southern Africa are known to harbor some of the deepest-rooting lineages of human mtDNA; however, their relationships are as yet poorly understood. Here, we report the results of analyses of complete mtDNA genome sequences from nearly 700 individuals representing 26 populations of southern Africa who speak diverse Khoisan and Bantu languages. Our data reveal a multilayered history of the indigenous populations of southern Africa, who are likely to be the result of admixture of different genetic substrates, such as resident forager populations and pre-Bantu pastoralists from East Africa. We find high levels of genetic differentiation of the Khoisan populations, which can be explained by the effect of drift together with a partial uxorilocal/multilocal residence pattern. Furthermore, there is evidence of extensive contact, not only between geographically proximate groups, but also across wider areas. The results of this contact, which may have played a role in the diffusion of common cultural and linguistic features, are especially evident in the Khoisan populations of the central Kalahari.

The genetic prehistory of southern Africa.

Southern and eastern African populations that speak non-Bantu languages with click consonants are known to harbour some of the most ancient genetic lineages in humans, but their relationships are poorly understood. Here, we report data from 23 populations analysed at over half a million single-nucleotide polymorphisms, using a genome-wide array designed for studying human history. The southern African Khoisan fall into two genetic groups, loosely corresponding to the northwestern and southeastern Kalahari, which we show separated within the last 30,000 years. We find that all individuals derive at least a few percent of their genomes from admixture with non-Khoisan populations that began ∼1,200 years ago. In addition, the East African Hadza and Sandawe derive a fraction of their ancestry from admixture with a population related to the Khoisan, supporting the hypothesis of an ancient link between southern and eastern Africa.