domingo, 21 de agosto de 2011
Há uma nova interpretação sobre os concheiros de Muge
Sítio arqueológico teve novas escavações
18.08.2011 - 17:51 Por Lusa in Público
A região onde está o sítio arqueológico dos concheiros de Muge, em Salvaterra de Magos, terá sido há 8000 anos um estuário semelhante ao de Lisboa, e as conchas terão sido colocados em algumas décadas para sinalizar e proteger o local que foi descoberto há 150 anos.
A convicção é de Nuno Bicho, responsável científico das escavações que decorrem há quatro anos no Cabeço da Amoreira, numa área equivalente a meio campo de futebol.
Os meios científicos actuais e o pormenor com que têm decorrido os trabalhos permitem novas interpretações sobre a ocupação do local e a comunidade que o habitou há cerca de 8000 anos, disse o arqueólogo à Lusa.
Além de contrariar a ideia de que os montes de conchas (resultantes de uma componente importante da alimentação daquela comunidade) foram sendo depositados ao longo de milénios, a equipa entende ainda que a comunidade de caçadores recolectores que ali se instalou era socialmente mais complexa do que se pensava.
Como exemplo, Nuno Bicho aponta o esqueleto encontrado no final de Julho - uma mulher jovem enterrada há cerca de 7500 anos - e que só o detalhe da escavação permitiu “ler” o conjunto de cuidados colocados no enterramento, revelando uma complexidade de rituais nunca antes registada, apesar dos mais de 300 esqueletos encontrados nas escavações anteriores neste sítio arqueológico.
“Agora poderíamos replicar o enterramento”, disse, referindo o processo de enterramento e pormenores, como a posição lateral do corpo com joelhos flectidos, uma mão sobre um joelho e outra sobre o peito, e a colocação criteriosa de conchas de berbigão e de lambujinha, três escápulas de veado, um fragmento de crânio de cão e alguns pequenos artefactos em pedra.
Para o arqueólogo, estes detalhes permitem vislumbrar a presença de uma sociedade mais complexa do ponto de vista social do que inicialmente se supunha, “com alguma hierarquização do ponto de vista etário e de género, com uns elementos mais importantes que outros, com funções específicas e umas mais dignificadas que outras”.
Por outro lado, Nuno Bicho refere que a informação trazida à luz pelas escavações mais recentes permite concluir que houve um interregno “talvez de 300 anos entre a ocupação e a deposição de conchas”, o que o leva a admitir que os descendentes da comunidade original, “por qualquer razão”, regressaram ao local para o proteger.
“Puseram as conchas num período muito rápido - não temos possibilidade de saber quão rápido, mas sabemos que essa tarefa não durou mais de 100 anos – e depois de outro interregno, talvez de 200 anos, foi colocado um manto pedregoso que protegeu e selou definitivamente o local”, deixando uma “marca territorial”, disse.
As escavações permitiram ainda concluir que, já depois da cobertura com conchas (que atinge uma altura de 2,5 metros) e depois da cobertura com pedras, houve enterramentos, acrescentou.
A escavação em curso, envolvendo investigadores e arqueólogos das Universidades do Algarve, de Coimbra, de Lisboa, do Porto e universidades do Canadá e de Inglaterra, teve um financiamento para três anos da Fundação para a Ciência e Tecnologia, renovado em 2009 por mais três anos, contando com o apoio da Casa Cadaval, em cujos terrenos se situam os concheiros.
Nuno Bicho espera culminar esta fase com a realização, em 2013, de uma reunião internacional para celebrar os 150 anos dos primeiros achados feitos no local.
Quaternary International
Earthquake Archaeology and Paleoseismology
Edited by P.G. Silva, M. Sintubin and Klaus Reicherter
quinta-feira, 11 de agosto de 2011
Ancient DNA reveals secrets of human history
Modern humans may have picked up key genes from extinct relatives
For a field that relies on fossils that have lain undisturbed for tens of thousands of years, ancient human genomics is moving at breakneck speed. Barely a year after the publication of the genomes of Neanderthals1 and of an extinct human population from Siberia2, scientists are racing to apply the work to answer questions about human evolution and history that would have been unfathomable just a few years ago.
The past months have seen a swathe of discoveries, from details about when Neanderthals and humans interbred, to the important disease-fighting genes that humans now have as a result of those trysts.
Neanderthals were large-bodied hunter-gatherers, named after the German valley where their bones were first discovered, who roamed Europe and parts of Asia from 400,000 years ago until about 30,000 years ago. The Neanderthal genome — shepherded by Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany — indicates that their evolutionary story began to split from the lineage of modern humans less than half a million years ago, when their common ancestor lived in Africa (see 'The human strain'). In December last year, Pääbo's team released the genetic blueprint of another population of ancient humans — unlike ourselves or the Neanderthals — that was based on DNA recovered from a 30,000–50,000-year-old finger bone found in a cave in Denisova in southern Siberia2. Palaeoanthropologists call these groups archaic humans, distinguishing them from modern Homo sapiens, which emerged in Africa only around 200,000 years ago.
Pääbo is amazed at how quickly the Neanderthal genome has been mined. At a genomics meeting last year, for example, Cory McLean, a graduate student at Stanford University in California, was scheduled to talk immediately after Pääbo presented the Neanderthal genome. Inspired, McLean had trawled through the just-released genome in the days before his talk. He discovered that Neanderthals, like humans, lacked a stretch of DNA that orchestrates the growth of spines on the penises of other primates, and promptly presented the find just after Pääbo presented his3.
Since then, scientists have fleshed out the details of one of the biggest surprises from the Neanderthal genome: humans living outside Africa owe up to 4% of their DNA to Neanderthals. One explanation might be that humans migrating out of Africa mated with Neanderthals, probably resident in the Middle East, before their offspring fanned out across Europe and Asia.
“These genomes are publicly available. There’s nothing stopping high-school students from doing this.” By comparing individual DNA letters in multiple modern human genomes with those in the Neanderthal genome, the date of that interbreeding has now been pinned down to 65,000–90,000 years ago. Montgomery Slatkin and Anna-Sapfo Malaspinas, theoretical geneticists from the University of California, Berkeley, presented the finding at the Society for Molecular Biology and Evolution meeting in Kyoto, Japan, held on 26–30 July.
Slatkin says that their result agrees with another study presented at the meeting that came from the group of David Reich, a geneticist at Harvard Medical School in Boston, Massachusetts, who was involved in sequencing both the Neanderthal and Denisova genomes. The dates also mesh with archaeological finds bookending early human migrations out of Africa to between about 50,000 and 100,000 years ago. Reich's team is now developing tools to find signs of more recent interbreeding that might have occurred after humans arrived in Asia and Europe.
More than genes
The denizens of Denisova also bred with contemporary humans, according to Pääbo and Reich's analysis2. But the only traces of their DNA to be found in modern humans were in residents of Melanesia, thousands of miles away from Denisova, suggesting that the Denisovans had once lived across Asia. In 2008, Pääbo's team set up a lab in Beijing to screen fossils that might contain Denisovan DNA, in the hope of learning more about them and their interactions with modern humans. Currently, the bone that yielded the Denisovan genome, and a single molar from the same cave, are their only known fossil remains, but other archaic human fossils from Asia could bear traces of this group.
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Most of the Neanderthal genome was sequenced from bones found in Vindija cave, Croatia. Max Planck Inst. Evol. Anthropol. |
er inspection of the Neanderthal genome. However, a study presented at a Royal Society symposium in London in June suggests that humans owe important disease-fighting genes to Neanderthals and Denisovans. Interbreeding endowed humans with a 'hybrid vigour' that helped them colonize the world, said Peter Parham, an immunogeneticist at Stanford University School of Medicine, California, at the symposium.
Parham's team compared a group of diverse immune genes — the human leukocyte antigen (HLA) genes — in Neanderthals, Denisovans and human groups from around the world. In several cases, Neanderthals and Denisovans carried versions of HLA genes that are abundant in modern humans in parts of Europe and Asia, but less common in Africans. Varying degrees of interbreeding could explain the mismatch, Parham says. He estimates that Europeans owe 50% of variants of one class of HLA gene to interbreeding, Asians 70–80%, and Papua New Guineans up to 95%.
"It does mean that some of us owe part of our immune-system function to Neanderthals," says Pääbo. However, John Hawks, a biological anthropologist at the University of Wisconsin-Madison, notes that many HLA genes pre-date humans' split from Neanderthals and Denisovans, and that the differences may have arisen by chance as the groups evolved.
Hawks, too, has been digging into the archaic genomes, and his team has already discovered that Neanderthals and Denisovans lack certain forms of genes that may help modern humans to fend off epidemic diseases, such as measles. This is hardly surprising: the low population density of hunter-gatherers meant that epidemics were unlikely, so they probably would not have benefited from these immune genes.
But Hawks's team is now using the find to test whether the defensive genes are linked to autoimmune diseases. In September, Hawks and his colleague Aaron Sams are scheduled to present data at a meeting of the European Society for the Study of Human Evolution in Leipzig, Germany, showing that the Denisovans lacked nearly all of the gene variants linked to coeliac disease, a gut autoimmune disorder present in modern humans. Hawks suspects that the variants may actually be in the same genes that are linked to epidemic resistance — if they are, further study could reveal how recently such autoimmune diseases arose in humans.
Unlike most scientists mining the ancient genomes, Hawks has reported some of his more prosaic findings — Denisovans didn't have red hair, for example — on his blog (see go.nature.com/irclra). "These genomes are publicly available. There's nothing stopping high-school students from doing this, and the kind of stuff that I'm putting out on my blog is the stuff that a smart high-school student could do." More significant (and closely guarded) insights will come from developing new methods for analysing ancient genomes to test hypotheses about evolution, he says.
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Pääbo, Reich and the other scientists involved in sequencing the ancient genomes are eager to see others run with their data, but caution that they need to be aware of the limitations. "They're really terrible-quality genomes", chock-full of gaps and errors and sections in which short stretches of DNA sequence have been put in the wrong place, says Reich. "There are a lot of traps in using these data, and if people are not careful they'll find all sorts of interesting things that are wrong." Pääbo's team is working on improving the quality of the sequences and including data from more Neanderthals and — he hopes — Denisovans.
Pääbo says that he and his team regularly receive e-mails from scientists asking them questions about using the ancient genomes, which they have attempted to make as user-friendly as possible. But if the first year of ancient human genomics is any indication, these requests will multiply as scientists find new applications for the genomes. "Maybe we should write a little booklet called archaic genomics for dummies," Pääbo says.
References
Green, R. E. et al. Science 328, 710-722 (2010). | Article | PubMed | ISI | ChemPort |
Reich, D. et al. Nature 468, 1053-1060 (2010). | Article | PubMed | ISI | ChemPort |
McLean, C. Y. et al. Nature 471, 216-219 (2011). | Article | PubMed | ISI | ChemPort |
Forma “moderna” de caminhar tem quatro milhões de anos
Pegadas de Laetoli serviram de base para novo estudo
in ciênciahoje 2011-07-20
As pegadas pré-históricos de Laetoli, na Tanzânia, serviram de base para os investigadores demonstrarem que os hominídeos que povoavam a região há 3,7 milhões de anos, os Australopithecus afarensis, caminhavam de forma mais semelhante às pessoas da actualidade do que aos primatas bípedes, como os chimpanzés ou os gorilas.
O estudo, que recorreu a simulações de computador para se prever a forma das pegadas do Australopithecus afarensis, foi publicado pelo “Journal of Royal Society”.
Estas pegadas são as marcas atribuídas aos ancestrais humanos mais antigas que se conhecem e estão conservadas em argila, graças às cinzas vulcânicas. No entanto, o desgaste que sofreram com a passagem do tempo deformou-as, o que desencadeou vários debates na comunidade científica sobre a forma de caminhar dos seus autores.
Embora os hominídeos tenham começado a andar sobre duas pernas há seis milhões de anos, alguns investigadores defendem que a marcha humana, com o corpo erguido e impulsionada pela parte da frente dos pés, começou com o Homo erectus, há 1,9 milhões de anos.
"Anteriormente pensava-se que o Australopithecus andava encurvado e que se impulsionava com a parte do meio do pé, como os grandes símios da actualidade”, referiu Robin Crompton, um dos autores deste estudo. "No entanto", prosseguiu, "as pegadas de Laetoli implicam uma forma de caminhar erecta e com a parte da frente do pé, muito parecida com a dos humanos de hoje."
segunda-feira, 11 de julho de 2011
EARLIEST EUROPEANS WERE CANNIBALS, WORE BLING
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Cut marks are seen on this early human bone recovered from southeastern Europe. L. Crépin - S. Prat / MNHN - CNRS |
The remains, described in PLoS One, date to 32,000 years ago and represent the oldest direct evidence for anatomically modern humans in a well-documented context. The human remains are also the oldest known for our species in Europe to show post-mortem cut marks.
"Our observations indicate a post-mortem treatment of human corpses including the selection of the skull," co-author Stephane Pean, a paleozoologist and archaeologist at the National Museum of Natural History in Paris, told Discovery News. "We demonstrate that this treatment was not for nutritional purposes, according to comparison with game butchery treatment, so it is not a dietary cannibalism."
Instead, Pean said that he and his colleagues believe that the "observed treatment of the human body, together with the presence of body ornaments, indicates rather a mortuary ritual: either a ritual cannibalism or a specific mortuary practice for secondary disposal."
The scientists made those assessments after studying human remains and artifacts discovered at a shelter-cave site called Buran-Kaya III in the Ukraine.
Although this is a more complete archaeological setting, the actual first known Homo sapiens from Europe dates to 34,000 years ago from Pestera cu Oase in Romania. Yet another single modern human from Kostenki 1 in Russia dates to 33,000 years ago.
The age of all of these discoveries intriguingly suggests that these first members of our species in Europe may have coexisted with Neanderthals.
"Through our work in progress, some of the expected results could help to better understand the transition period of late Neanderthal and early Homo sapiens settlements in Europe," Pean said.
While the possible Neanderthal connection remains a mystery, it is more evident that these early anatomically modern humans wore mammoth bling.
Artifacts excavated at the site include five mammoth beads, one engraved plate made out of mammoth ivory and 35 perforated shells. Since no mammoth remains or craft debris were found, it's likely that the objects were made off-site.
The remains of pointed bone tools and stone projectiles indicate these early Europeans were active hunters with busy associated tool and weapon-making industries.
The discoveries support that the hunter-gatherers "repeatedly settled the rock shelter of Buran-Kaya III as a temporary hunting camp, and they mostly hunted saiga antelopes," Pean said.
Marcel Otte, a professor of prehistory at the University of Liege, has also excavated at Buran-Kaya III. He told Discovery News that he and his team found evidence for a 30,000-year-old culture at the same site, indicating the region was continuously inhabited for thousands of years after the first modern humans arrived.
Marylene Patou-Mathis, director of the Archaeozoology Unit at the National Museum of Natural History in Paris, told Discovery News that Pean and colleagues' "paper is very important and I agree with the results, which are absolutely new. I am particularly interested in the traces of cannibalism, which are well demonstrated."
She is also interested in the possible Neanderthal connections.
Patou-Mathis explained, "The area of Crimea, with the site of Buran Kaya and another site, Siuren, is very important to question the coexistence of two humankinds, Neanderthal and Homo sapiens, and two cultures on the same territory."
Pean and his team are currently involved in another dig at the same site, "so we are expecting new discoveries," he said.
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