Science: Modern man not so modern

 作者:包秩燕     |      日期:2019-03-04 03:02:01
By SARAH BUNNEY ARCHAEOLOGISTS often have to go over old ground. But, by applying new techniques to old finds – often discovered many decades ago – they sometimes turn up surprises. Archaeologists working in Spain have done just that. By dating two well-known cave sites using accelerator mass spectroscopy, which is much more accurate than the conventional method of carbon dating, the team has produced new dates that challenge notions about when Neanderthals disappeared and modern people first appeared in western Europe. The new dates suggest that anatomically modern people (Homo sapiens sapiens) were present in western Europe at least 40 000 years ago. Previously, archaeologists believed thatearly modern Europeans, or CroMagnons, appeared between35 000 and 30 000 years ago. The dates for the two Spanish sites, together with evidence from other parts of Europe, also suggest that in some regions of Europe Neanderthals were superseded very quickly by more modern-looking humans, while in other regions the two populations overlapped for as long as several thousand years. In the Middle East, the two forms may have coexisted for tens oft housands of years (see New Scientist, Science, 26 November 1987 and 25 February 1988). Although some archaeologists believe that modern Europeans are descended directly from Neanderthals, more subscribe to the view that the Neanderthal line of evolution contributed little or nothing at all to the modern European stock, and that all Neanderthals died out between 40,000 and 30,000 years ago. Proponents of this view hold that Neanderthals were replaced by modern people who originated in Africa between 200,000 and 100,000 years ago and migrated to Europe and Asia by way of the Levant (the region bordering the eastern Mediterranean in present-day Israel, Lebanon and Syria). Skeletal remains provide good evidence of early modern humans in Israel (Qafzeh and Skhu-l caves) between 100,000 and 90,000 years ago. By at least 43,000 years ago, populations of modern people had reached southern and central Europe. According to James Bischoff of the US Geological Survey and four Spanish colleagues, it took only a relatively short time for early modern people to migrate to Spain. According to the new dates, they reached the two Spanish caves (L’Arbreda in Catalonia and El Castillo in Cantabria) around 40,000 years ago (Journal of Archaeological Science, vol 16, pp 563 and 577). Both caves had previously been used by Neanderthals. Bischoff and his colleagues dated fragments of charcoal within the layers of sediment in the caves. The charcoal provided dates, and tools found in the various layers provided clues to the identities of its occupants. Most researchers accept that where there are no skeletal remains, the telltale sign of the first modern Europeansis a type of stone tool technology calledthe Aurignacian. This technology is quite different from that associated with Neanderthals, which is known as Mousterian technology. Aurignacian toolmakers were markedly more innovative than Mousterian toolmakers, not only in the materials and methods of manufacture they used, but also in the range of forms they made and the speed at which they adopted new techniques. Modern people made extensive use of antler, bone and ivory, not just for tools but also for ornament and art objects. They made long narrow blades as the first stepin creating specialised tools, such as endscrapers and burins. The toolmakers travelled long distances to obtain special materials, such as marine shells and flints. Very likely, there were also marked differences in the social behaviour and the hunting strategies of the makers of the two types of tools. The first appearance of Aurignacian artefacts in the archaeological record marks the start of the cultural period known as the Upper Palaeolithic. Tools of this type have been found throughout western, central and eastern Europe, and also in the Levant. The textbooks say that in western Europe the Upper Palaeolithic began around 35 000 years ago, at which point early modern humans were present. Bischoff and his colleagues’ new findings mean that the textbooks will have to change. It is likely, however, that some of the dates for the appearance of early modern humans in eastern Europe are also too recent. If they too are dated again, this time by accelerator mass spectroscopy, the picture could change still further – altering our view of the speed at which people migrated from eastern to western Europe. At El Castillo and L’Arbreda, Bischoff and his colleagues found Aurignacian tools at several levels in the sediment. Fragments of charcoal in the earliest of these levels gave dates of between 40 000 and 37 700 years ago. The dates for the two sites, which are 550 kilometres apart, are remarkably consistent, although the sequence of occupation at the sites is different. At L’Arbreda cave, northwest of Gerona, the earliest layers containing Aurignacian tools are preceded without any break by beds containing Mousterian or ‘Middle Palaeolithic’ tools. There are no clues to what happened to the Neanderthals. They could have stopped using the cave for all sorts of reasons: they could have been driven away or killed by modern people or they might have left the area before the CroMagnons arrived on the scene. The difference between the two cultures at L’Arbreda is ‘particularly striking’, say Bischoff and colleagues. The Neanderthal tools are mostly made from local quartz and quartzite; most of the Aurignacian tools are made from flint brought to the cave from some distance away. There is further evidence that the Middle Palaeolithic technology ended around 40,000 years ago, from another site, the Abric Romani rock shelter, near Barcelona. Bischoff and his colleagues conclude from this that modern people rapidly replaced the Neanderthals in the Catalonian region 40,000 years ago. The second site, El Castillo cave to the southwest of Santander, also shows signs of Neanderthal occupation, but here the Mousterian artefacts are separated from the succeeding Aurignacian tools by a layer of sediment half a metre thick that has no archaeological remains in it at all. Clearly, here the Neanderthals had stopped using this cave some time before modern people appeared. In southwestern France and along the northernmost coast of Spain, as in the Middle East, there are signs that modern people and Neanderthals lived side by side for a time. There is no abrupt transition as at L’Arbreda. Evidence for this view comes from the existence at several sites of a distinctive technology called the Chatelperronian, which shows features of both the Mousterian and the Aurignacian technologies. A good example of such a technology was associated with a Neanderthal skeleton at Saint-Cesaire in Charente-Maritime. Some archaeologists, including Paul Mellars of the University of Cambridge, suggest that this technology was practised by Neanderthal groups who survived in pockets of Europe after the arrival of modern humans. Either independently or through contact with the more modern humans, the culture of these Neanderthals acquired some of the trademarks of the Aurignacian (Current Anthropology, vol 30, p 349). This is a controversial issue,