Les populations d'Homo Erectus étaient réduites.

[JacquesL]

Pour lire et comprendre l'article, ou du moins son résumé, un premier problème se pose au profane : l'expression "mobile elements" en génétique.

Premiers liens trouvés :
http://en.wikipedia.org/wiki/Mobile_genetic_elements
qui renvoie à :
http://en.wikipedia.org/wiki/Transposon
http://en.wikipedia.org/wiki/Retrotransposons
http://en.wikipedia.org/wiki/Insertion_sequences
http://en.wikipedia.org/wiki/Plasmids
http://en.wikipedia.org/wiki/Bacteriophage
http://en.wikipedia.org/wiki/Group_II_intron
http://www.ncbi.nlm.nih.gov/pubmed/15016989

Science. 2004 Mar 12;303(5664):1626-32.
Mobile elements: drivers of genome evolution.

Kazazian HH Jr.

Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA. kazazian@mail.med.upenn.edu

Mobile elements within genomes have driven genome evolution in diverse ways. Particularly in plants and mammals, retrotransposons have accumulated to constitute a large fraction of the genome and have shaped both genes and the entire genome. Although the host can often control their numbers, massive expansions of retrotransposons have been tolerated during evolution. Now mobile elements are becoming useful tools for learning more about genome evolution and gene function.

PMID: 15016989

Ceci réglé :
http://www.pnas.org/content/107/5/2147.abstract?sid=3b5019b7-53bc-40ff-9469-d76c8ec7c790

Mobile elements reveal small population size in the ancient ancestors of Homo sapiens

  1. Chad D. Huffa,
  2. Jinchuan Xinga,
  3. Alan R. Rogersb,
  4. David Witherspoona, and
  5. Lynn B. Jordea,1

+ Author Affiliations

  1.
     aDepartment of Human Genetics, Eccles Institute of Human Genetics,
  2.
     bDepartment of Anthropology, University of Utah, Salt Lake City, UT 84112

  1.

     Edited* by Wen-Hsiung Li, University of Chicago, Chicago, IL, and approved December 18, 2009 (received for review August 11, 2009)

Abstract

The genealogies of different genetic loci vary in depth. The deeper the genealogy, the greater the chance that it will include a rare event, such as the insertion of a mobile element. Therefore, the genealogy of a region that contains a mobile element is on average older than that of the rest of the genome. In a simple demographic model, the expected time to most recent common ancestor (TMRCA) is doubled if a rare insertion is present. We test this expectation by examining single nucleotide polymorphisms around polymorphic Alu insertions from two completely sequenced human genomes. The estimated TMRCA for regions containing a polymorphic insertion is two times larger than the genomic average (P < <10−30), as predicted. Because genealogies that contain polymorphic mobile elements are old, they are shaped largely by the forces of ancient population history and are insensitive to recent demographic events, such as bottlenecks and expansions. Remarkably, the information in just two human DNA sequences provides substantial information about ancient human population size. By comparing the likelihood of various demographic models, we estimate that the effective population size of human ancestors living before 1.2 million years ago was 18,500, and we can reject all models where the ancient effective population size was larger than 26,000. This result implies an unusually small population for a species spread across the entire Old World, particularly in light of the effective population sizes of chimpanzees (21,000) and gorillas (25,000), which each inhabit only one part of a single continent.

   * human effective population size
   * human evolutionary history
   * Alu
   * coalescent theory
   * population genetics

Footnotes

   * 1To whom correspondence should be addressed. Email: lbj@odin.genetics.utah.edu.
   *

     Author contributions: C.D.H. designed research; C.D.H., J.X., A.R.R., and D.J.W. performed research; C.D.H. and J.X. contributed new reagents/analytic tools; C.D.H. and D.J.W. analyzed data; and C.D.H., J.X., A.R.R., D.J.W., and L.B.J. wrote the paper.
   *

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