Ayala F J, Rzhetsky A, Ayala F J
Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park 16802, USA.
Proc Natl Acad Sci U S A. 1998 Jan 20;95(2):606-11. doi: 10.1073/pnas.95.2.606.
The time of origin of the animal phyla is controversial. Abundant fossils from the major animal phyla are found in the Cambrian, starting 544 million years ago. Many paleontologists hold that these phyla originated in the late Neoproterozoic, during the 160 million years preceding the Cambrian fossil explosion. We have analyzed 18 protein-coding gene loci and estimated that protostomes (arthropods, annelids, and mollusks) diverged from deuterostomes (echinoderms and chordates) about 670 million years ago, and chordates from echinoderms about 600 million years ago. Both estimates are consistent with paleontological estimates. A published analysis of seven gene loci that concludes that the corresponding divergence times are 1,200 and 1,000 million years ago is shown to be flawed because it extrapolates from slow-evolving vertebrate rates to faster-evolving invertebrate rates, as well as in other ways.
动物门的起源时间存在争议。从5.44亿年前开始的寒武纪发现了来自主要动物门的丰富化石。许多古生物学家认为，这些门起源于新元古代晚期，即寒武纪化石爆发前的1.6亿年。我们分析了18个蛋白质编码基因位点，估计原口动物（节肢动物、环节动物和软体动物）与后口动物（棘皮动物和脊索动物）大约在6.7亿年前分化，而脊索动物与棘皮动物大约在6亿年前分化。这两个估计都与古生物学估计一致。一项已发表的对七个基因位点的分析得出结论，相应的分化时间分别为12亿年和10亿年前，结果显示该分析存在缺陷，因为它从进化缓慢的脊椎动物速率推断到进化较快的无脊椎动物速率，以及在其他方面也存在问题。
