quinta-feira, novembro 16, 2006

Genoma dos neandertais mostra que não são nossos avós

É um debate que dura há 150 anos: o homem de Neandertal é, ou não, nosso avô? Mais do que não haver consenso, o assunto tira do sério muita gente na comunidade científica. Amanhã, o debate promete voltar a animar-se, com a publicação da análise mais completa feita até agora de ADN de Neandertal.

E a história que conta é que eles não são nossos avós — ou, se neandertais e homens modernos, a nossa espécie, fizeram sexo, isso acabou por ter pouca influência no genoma humano.

Não é a primeira vez que se obtém e analisa ADN de neandertais. A estreia foi em 1997, quando a equipa de Svante Pääbo (do Instituto Max Planck para a Antropologia da Evolução, na Alemanha) reduziu a pó uma secção de 3,5 gramas do úmero de um Neandertal. Eram amostras do primeiro Neandertal descoberto em 1856, no vale (Tal, em alemão) de Neander, perto de Düsseldorf, na Alemanha.

Essas amostras eram apenas de ADN das mitocôndrias, estruturas responsáveis pela produção de energia celular, que se encontram fora do núcleo das células (é no núcleo que está o grosso da informação genética, mas é mais fácil recuperar ADN mitocondrial antigo).

Tantos os resultados das análises do “primeiro” Neandertal, como de outros 11 indivíduos (encontrados na Alemanha, Rússia, Croácia, Bélgica, França, Itália e Espanha), deram sempre muita discussão. “Não havia provas de contribuição genética para os humanos modernos”, recordou Pääbo, numa conferência de imprensa para apresentação das novas análises.

Havia que recuperar o precioso ADN do núcleo e analisá-lo. É o que a equipa de Pääbo anuncia agora na revista Nature. Teste a ossos da CroáciaTestaram ossos e dentes de mais de 70 Neandertais encontrados na Europa e Ásia ocidental, à procura de amostras que não estivessem contaminadas por ADN de humanos modernos. Obtiveram-nas do fóssil com 38 mil anos, descoberto em 1980 na gruta de Vindija, na Croácia.

Teresa Firmino

Notícia completa: http://www.publico.clix.pt/shownews.asp?id=1276725
Notícia original: Nature

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