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 Post subject: Neanderthals
PostPosted: Sun Jun 27, 2010 8:04 pm 
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Joined: Thu Jun 24, 2010 2:33 pm
Posts: 116
Public release date: 23-Jun-2010

Separation between Neanderthal and Homo sapiens might have occurred 500,000 years earlier

The separation of Neanderthal and Homo sapiens might have occurred at least one million years ago, more than 500.000 years earlier than previously believed after DNA-based analyses. A doctoral thesis conducted at the National Center for Research on Human Evolution (Centro Nacional de Investigación sobre la Evolución Humana) -associated with the University of Granada-, analysed the teeth of almost all species of hominids that have existed during the past 4 million years. Quantitative methods were employed and they managed to identify Neanderthal features in ancient European populations.

The main purpose of this research –whose author is Aida Gómez Robles- was to reconstruct the history of evolution of Human species using the information provided by the teeth, which are the most numerous and best preserved remains of the fossil record. To this purpose, a large sample of dental fossils from different sites in Africa, Asia and Europe was analysed. The morphological differences of each dental class was assessed and the ability of each tooth to identify the species to which its owner belonged was analysed.

The researcher concluded that it is possible to correctly determine the species to which an isolated tooth belonged with a success rate ranging from 60% to 80%. Although these values are not very high, they increase as different dental classes from the same individual are added. That means that if several teeth from the same individual are analysed, the probability of correctly identifying the species can reach 100%.

Aida Gómez Robles explains that, from all the species of hominids currently known "none of them has a probability higher than 5% to be the common ancestor of Neardenthals and Homo sapiens. Therefore, the common ancestor of this lineage is likely to have not been discovered yet".

http://www.eurekalert.org/pub_releases/ ... 062310.php


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 Post subject: Re: Neanderthals
PostPosted: Wed Jun 30, 2010 1:10 am 
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Joined: Thu Jun 24, 2010 10:37 pm
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Common ancestor not yet found

A doctoral study performed at the Centro Nacional de Investigacion sobre la Evolucion Humana, University of Granada (Spain) attempted to reconstruct the history of human evolution by performing analyses on teeth from almost all species of hominids that have lived. Going back over 4 million years, the morphology of dental fossils from Asia, Africa and Europe was compared.
A statistical analysis was done to determine the probabilty of correctly assigning each tooth to the species from which it was taken. The results revealed Neanderthal features in ancient European populations. But, according to Aida Gomez Robles, the author of the study, "None of (the samples) has a probability higher than 5% to be the common ancestor of Neanderthals and Homo sapiens. Therefore, the common ancestor of this lineage is likely to have not been discovered yet." This could put the divergence of the two species 500,000 years earlier than previously believed based upon genetic studies.
The analysis techniques used in the study allowed researchers to correctly assign a species to the tooth sample 60 to 80 percent of the time. If multiple teeth were analysed from the same individual, the success rate rose up to 100 percent in some cases.
This project employed cutting edge computer simulations to mathematically model the effect of environmental changes on tooth shape. The technique has been used in the past to study other mammals, but never in human evolution.
Robles used fossils from sites as diverse as Burgos (Spain), and Dmanisi (Republic of Georgia), as well as collections in Paris, Frankfurt, Berlin, Beijing, New York and Cleveland. The research was published in The Journal of Human Evolution, 2007 and 2008.


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