New Statistical Model Moves Human Evolution Back Three Million Years
ScienceDaily (Nov. 5, 2010) — Evolutionary divergence of humans and chimpanzees likely occurred some 8 million years ago rather than the 5 million year estimate widely accepted by scientists, a new statistical model suggests.
A new statistical model suggests that evolutionary divergence of humans from chimpanzees likely occurred some 8 million years ago, rather than the 5 million year estimate widely accepted by scientists. (Credit: iStockphoto/Eric Gevaert)
The revised estimate of when the human species parted ways from its closest primate relatives should enable scientists to better interpret the history of human evolution, said Robert D. Martin, curator of biological anthropology at the Field Museum, and a co-author of the new study appearing in the journal Systematic Biology.
Working with mathematicians, anthropologists and molecular biologists, Martin has long sought to integrate evolutionary information derived from genetic material in various species with the fossil record to get a more complete picture.
Comparing DNA among related animals can provide a clear picture of how their shared genes evolved over time, giving rise to new and separate species, Martin said. But such molecular information doesn't yield a timetable showing when the genetic divergence occurred.
Fossil evidence is the only direct source of information about long-extinct species and their evolution, Martin and his colleagues said, but large gaps in the fossil record can make such information difficult to interpret. For a generation, paleontologists have estimated human origins at 5 million to 6 million years ago.
But that estimate rests on a thin fossil record. By looking at all of today's primate species, all of the known fossil primates and using DNA evidence, computer models suggest a longer evolutionary timetable. The new analysis described in the Systematic Biology paper takes into account gaps in the fossil record and fills in those gaps statistically.
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Systematic Biology
Dating Primate Divergences through an Integrated Analysis of Palaeontological and Molecular Data
Richard D. Wilkinson1,*, Michael E. Steiper2,3,4,5, Christophe Soligo6, Robert D. Martin7, Ziheng Yang8 and Simon Tavaré9
+Author Affiliations
1School of Mathmatical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
2Department of Anthropology, Hunter College, City University of New York, NY 10065-5024, USA
3Program in Anthropology, The Graduate Center, City University of New York, NY 10016-4309, USA
4Program in Biology, The Graduate Center, City University of New York, NY 10016-4309, USA
5New York Consortium in Evolutionary Primatology New York, NY, USA
6Department of Anthropology, University College London, 14 Taviton Street, London WC1H 0BW, UK
7Department of Anthropology, The Field Museum, 1400 S. Lake Shore Drive, Chicago 60605-2496, IL, USA
8Department of Biology, University College London, Gower Street, London WC1E 6BT, UK
9Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
*Correspondence to be sent to: School of Mathmatical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK, E-mail: r.d.wilkinson@nottingham.ac.uk.
Received March 29, 2010.
Revision received May 26, 2010.
Accepted July 17, 2010.
Abstract
Estimation of divergence times is usually done using either the fossil record or sequence data from modern species. We provide an integrated analysis of palaeontological and molecular data to give estimates of primate divergence times that utilize both sources of information. The number of preserved primate species discovered in the fossil record, along with their geological age distribution, is combined with the number of extant primate species to provide initial estimates of the primate and anthropoid divergence times. This is done by using a stochastic forwards-modeling approach where speciation and fossil preservation and discovery are simulated forward in time. We use the posterior distribution from the fossil analysis as a prior distribution on node ages in a molecular analysis. Sequence data from two genomic regions (CFTR on human chromosome 7 and the CYP7A1 region on chromosome 8) from 15 primate species are used with the birth–death model implemented in mcmctree in PAML to infer the posterior distribution of the ages of 14 nodes in the primate tree. We find that these age estimates are older than previously reported dates for all but one of these nodes. To perform the inference, a new approximate Bayesian computation (ABC) algorithm is introduced, where the structure of the model can be exploited in an ABC-within-Gibbs algorithm to provide a more efficient analysis.
Key words
Approximate Bayesian computation, molecular phylogeny, palaeontological data, primate divergence
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Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao site CAPES/Periódicos podem ler gratuitamente este artigo da Systematic Biology e de mais 22.440 publicações científicas.
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Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao site CAPES/Periódicos podem ler gratuitamente este artigo da Systematic Biology e de mais 22.440 publicações científicas.
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CUTUCANDO O MEC/SEMTEC/PNLEM COM VARA COMPRIDA:
Com as inferências sobre a evolução humana mudando a cada década, que tal colocar uma nota nos livros didáticos de Biologia do ensino médio:
O MEC/SEMTEC/PNLEM ADVERTE: Tendo em vista as dificuldades empírico-teóricas que esta área científica sofre, destacamos para os alunos que inferência não é evidência que corrobore uma teoria, hipótese ou ideia científica.
Traduzindo em graúdos: É CHUTE EPISTÊMICO!!!
