Takahata N, Satta Y
The Graduate University for Advanced Studies, Hayama, Kanagawa 240-01, Japan.
Proc Natl Acad Sci U S A. 1997 Apr 29;94(9):4811-5. doi: 10.1073/pnas.94.9.4811.
To date major divergences that occurred in the primate lineage leading to modern humans and to infer a demographic parameter (effective population size) of the ancestral lineage that existed at each divergence, a maximum likelihood method was applied to autosomal DNA sequence data currently available for pairs of orthologous genes between the human and each of the chimpanzee, gorilla, Old World monkey (OWM), and New World monkey (NWM). A statistical test is carried out to support the assumption that silent substitutions have accumulated in a clock-like fashion over loci between primate taxa or even among sites within a locus. It is shown that the human ancestral lineage became distinct from the NWM 57.5 million years (Myr) ago, the OWM 31 Myr ago, the gorilla 8.0 Myr ago, and the chimpanzee 4.5 Myr ago, and that the effective population size at these divergences was generally much greater than that of modern humans. It is argued that the human ancestral lineage branched off from the NWM and OWM earlier than once thought and that significant demographic changes might have occurred at different evolutionary stages, particularly at the hominid stage.
迄今为止，为了确定在导致现代人类的灵长类谱系中发生的主要分歧，并推断每次分歧时存在的祖先谱系的一个人口统计学参数（有效种群大小），一种最大似然方法被应用于目前可获得的人类与黑猩猩、大猩猩、旧世界猴（OWM）和新世界猴（NWM）中每一种的直系同源基因对的常染色体DNA序列数据。进行了一项统计检验，以支持这样的假设：沉默替代以类似时钟的方式在灵长类分类群之间的基因座上甚至在一个基因座内的位点之间积累。结果表明，人类祖先谱系在5750万年前（Myr）与新世界猴分化，在3100万年前与旧世界猴分化，在800万年前与大猩猩分化，在450万年前与黑猩猩分化，并且在这些分歧时的有效种群大小通常比现代人类的大得多。有人认为，人类祖先谱系从新世界猴和旧世界猴分化出来的时间比以前认为的要早，并且在不同的进化阶段可能发生了重大的人口统计学变化，特别是在人科动物阶段。
