生物谷報道：牛津大學的科學家近日在《美國人類遺傳學雜志》發(fā)表研究論文，利用貝葉斯算法估算線粒體替代率,，結果支持“人類走出非洲”的時間和線粒體水平上的“人類共同祖先”的生存年代,，該時間晚于先前估計的時間,。
準確地估計線粒體替代率是人類分子進化研究的核心內容。但因為先前的研究采用了大量不同的方法和數據組合,，使得比較研究存在一定困難,。
故此，牛津大學的科學家根據177個人類線粒體基因組的一組數據,，使用松散分子鐘的貝葉斯系統進化分析方法,，估計了不同數據組合的替代率。科學家比較了多重內校準（生物地理）和傳統的外校準（人猿分化）的結果,。研究結果表明,，使用不同的數據組合和較準方法計算得到的替代率和分化時間相差很大?？傮w上,，研究支持“人類走出非洲”的時間和線粒體水平上的“人類共同祖先”的生存年代，該時間晚于先前估計的時間,。這項研究與考古學和解剖學水平的研究結果一致,，也得到源于核DNA和線粒體DNA的新年代學研究結果的支持?？茖W家們也證實人類線粒體基因組表現出一定的分子進化復雜性,，這需要在線粒體人類分子進化的研究中使用復雜的遺傳分子模型。（生物谷www.bioon.com）
生物谷推薦原始出處：
The American Journal of Human Genetics,，Volume 82, Issue 4, 895-902,，Phillip Endicott，Simon Y.W. Ho
A Bayesian Evaluation of Human Mitochondrial Substitution Rates
Phillip Endicott1 and Simon Y.W. Ho1, 2,
1 Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
2 Present address: Centre for Macroevolution and Macroecology, School of Botany and Zoology, Australian National University, Canberra ACT 0200, Australia.
Abstract
Accurate estimates of mitochondrial substitution rates are central to molecular studies of human evolution, but meaningful comparisons of published studies are problematic because of the wide range of methodologies and data sets employed. These differences are nowhere more pronounced than among rates estimated from phylogenies, genealogies, and pedigrees. By using a data set comprising mitochondrial genomes from 177 humans, we estimate substitution rates for various data partitions by using Bayesian phylogenetic analysis with a relaxed molecular clock. We compare the effect of multiple internal calibrations with the customary human-chimpanzee split. The analyses reveal wide variation among estimated substitution rates and divergence times made with different partitions and calibrations, with evidence of substitutional saturation, natural selection, and significant rate heterogeneity among lineages and among sites. Collectively, the results support dates for migration out of Africa and the common mitochondrial ancestor of humans that are considerably more recent than most previous estimates. Our results also demonstrate that human mitochondrial genomes exhibit a number of molecular evolutionary complexities that necessitate the use of sophisticated analytical models for genetic analyses.
