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      The Microcephalin Ancestral Allele in a Neanderthal Individual

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          Abstract

          Background

          The high frequency (around 0.70 worlwide) and the relatively young age (between 14,000 and 62,000 years) of a derived group of haplotypes, haplogroup D, at the microcephalin ( MCPH1) locus led to the proposal that haplogroup D originated in a human lineage that separated from modern humans >1 million years ago, evolved under strong positive selection, and passed into the human gene pool by an episode of admixture circa 37,000 years ago. The geographic distribution of haplogroup D, with marked differences between Africa and Eurasia, suggested that the archaic human form admixing with anatomically modern humans might have been Neanderthal.

          Methodology/Principal Findings

          Here we report the first PCR amplification and high- throughput sequencing of nuclear DNA at the microcephalin ( MCPH1) locus from Neanderthal individual from Mezzena Rockshelter (Monti Lessini, Italy). We show that a well-preserved Neanderthal fossil dated at approximately 50,000 years B.P., was homozygous for the ancestral, non-D, allele. The high yield of Neanderthal mtDNA sequences of the studied specimen, the pattern of nucleotide misincorporation among sequences consistent with post-mortem DNA damage and an accurate control of the MCPH1 alleles in all personnel that manipulated the sample, make it extremely unlikely that this result might reflect modern DNA contamination.

          Conclusions/Significance

          The MCPH1 genotype of the Monti Lessini (MLS) Neanderthal does not prove that there was no interbreeding between anatomically archaic and modern humans in Europe, but certainly shows that speculations on a possible Neanderthal origin of what is now the most common MCPH1 haplogroup are not supported by empirical evidence from ancient DNA.

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          Most cited references40

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          Assessing ancient DNA studies.

          The study of ancient DNA has the potential to make significant and unique contributions to ecology and evolution. However, the techniques used contain inherent problems, particularly with regards to the generation of authentic and useful data. The solution currently advocated to reduce contamination and artefactual results is to adopt criteria for authentication. Nevertheless, these criteria are not foolproof, and we believe that they have, in practice, replaced the use of thought and prudence when designing and executing ancient DNA studies. We argue here that researchers in this field must take a more cognitive and self-critical approach. Specifically, in place of checking criteria off lists, researchers must explain, in sufficient enough detail to dispel doubt, how the data were obtained, and why they should be believed to be authentic.
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            The hidden side of invasions: massive introgression by local genes.

            Despite hundreds of reports involving both plants and animals, the mechanisms underlying introgression remain obscure, even if some form of selection is frequently invoked. Introgression has repeatedly been reported in species that have recently colonized a new habitat, suggesting that demographic processes should be given more attention for understanding the mechanisms of introgression. Here we show by spatially explicit simulations that massive introgression of neutral genes takes place during the invasion of an occupied territory if interbreeding is not severely prevented between the invading and the local species. We also demonstrate that introgression occurs almost exclusively from the local to the invading species, especially for populations located far away from the source of the invasion, and this irrespective of the relative densities of the two species. This pattern is strongest at markers experiencing reduced gene flow, in keeping with the observation that organelle genes are often preferentially introgressed across species boundaries. A survey of the literature shows that a majority of published empirical studies of introgression during range expansions, in animals and in plants, follow the predictions of our model. Our results imply that speciation genes can be identified by comparing genomes of interfertile native and invading species pairs.
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              DNA sequences from multiple amplifications reveal artifacts induced by cytosine deamination in ancient DNA.

              We show that DNA molecules amplified by PCR from DNA extracted from animal bones and teeth that vary in age between 25 000 and over 50 000 years carry C-->T and G-->A substitutions. These substitutions can reach high proportions among the molecules amplified and are due to the occurrence of modified deoxycytidine residues in the template DNA. If the template DNA is treated with uracil N-glycosylase, these substitutions are dramatically reduced. They are thus likely to result from deamination of deoxycytidine residues. In addition, 'jumping PCR', i.e. the occurrence of template switching during PCR, may contribute to these substitutions. When DNA sequences are amplified from ancient DNA extracts where few template molecules initiate the PCR, precautions such as DNA sequence determination of multiple clones derived from more than one independent amplification are necessary in order to reduce the risk of determination of incorrect DNA sequences. When such precautionary measures are taken, errors induced by damage to the DNA template are unlikely to be more frequent than approximately 0.1% even under the unlikely scenario where each amplification starts from a single template molecule.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2010
                14 May 2010
                : 5
                : 5
                : e10648
                Affiliations
                [1 ]Dipartimento di Biologia Evoluzionistica, Laboratori di Antropologia, Università di Firenze, Firenze, Italy
                [2 ]Istituto di Tecnologie Biomediche, Consiglio Nazionale delle Ricerche (ITB-CNR), Segrate (MI), Italy
                [3 ]Dipartimento di Scienze Ambientali “G. Sarfatti”, UR: Ecologia Preistorica, Università di Siena, Siena, Italy
                [4 ]Museo di Storia Naturale di Verona - Sezione di Preistoria, Verona, Italy
                [5 ]Laboratoire d'Anthropologie Bio-culturelle, UMR6578 Université de la Méditerranée -CNRS-EFS, Marseille, France
                [6 ]Paleogenetics and Molecular Evolution, Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Lyon 1, CNRS, INRA, Ecole Normale Supérieure de Lyon, Lyon, France
                [7 ]Dipartimento di Biologia ed Evoluzione, Università di Ferrara, Ferrara, Italy
                University of Wisconsin, United States of America
                Author notes

                Conceived and designed the experiments: ML GB DC. Performed the experiments: ML ER LM G. Corti CB SV G. Catalano EP LL SC PG GDB DC. Analyzed the data: ML ER G. Corti GDB LO GB DC. Contributed reagents/materials/analysis tools: CH LO. Wrote the paper: ML LO GB DC.

                Article
                10-PONE-RA-15630R1
                10.1371/journal.pone.0010648
                2871044
                20498832
                a9e4c5ff-83c5-4e73-90a3-f5d48632e342
                Lari et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
                History
                : 19 January 2010
                : 23 April 2010
                Page count
                Pages: 6
                Categories
                Research Article
                Evolutionary Biology
                Evolutionary Biology/Genomics
                Evolutionary Biology/Human Evolution

                Uncategorized
                Uncategorized

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