Denis' cave in southern Siberia has been home to Neanderthals and Denis for thousands of years, but questions remain about the timing of their stay. Few new studies record the history of archaic occupation in the field, showing who lived there and when – including a possible era during which two extinct species hung together.
Two articles published today in nature represent an updated timeline for the occupation of Denis' Cave Neanderthals and Denizens. New research suggests that Denis – a sister species for Neanderthals – made this cave a home longer than Neanderthal, first appeared in the cave 287,000 years ago. Neanderthals arrived at the site about 140,000 years ago, probably sharing the denizens for thousands of years. It is another proof that the Neanderthals and the Denisans have enjoyed each other – and that it happened in or near Denis.
Archaeologists and paleontologists have been carefully intermingled through Denis Cave for 40 years and dragging various animal and Neanderthal bones. But the real bomb came in 2010 with the discovery of finger bones from a previously unknown human species, the so-called Denis. Genetic analysis suggests that the Denizs are related species to Neanderthals, but almost everything else remains a mystery to them, as if they first appeared on the scene and when they died.
The Denis Cave, located at the foot of the Altai Mountains in southern Siberia, is therefore a critical source for improving our understanding not only of the Denizs but also of the Neanderthals. And maybe our own kind, Homo sapiens– though the cave, perhaps strangely, did not provide any evidence to show that an anatomically modern person lives. For the Neanderthal and Denis, Denis' cave served as an important refuge for a huge amount of time.
Extensive times of time, really. We have not spoken here for a thousand years. Rather, we are talking about hundreds of thousands of years of employment. Compiling the timeline of events, such as when the cave was occupied for the first time and anyone, proved to be difficult, partly because of the large size of the cave and its complex layers of sediment; Stratigraphy of the cave includes the Siberian Central American period (340,000 and 45,000 years ago) and the early Upper Paleolithic period (roughly 45,000 to 40,000 years).
Scientists have also been confronted with limits on radiocarbon dating, which can return up to 50,000 years. The cave was inhabited much longer than that, requiring the use of less reliable dating methods and consequently the location of unconvincing or controversial time horizons.
To overcome these obstacles and limitations, a multidisciplinary team of researchers from around the world, including Russia, Great Britain, Australia, Germany and Canada, who analyzed the bones and artifacts found in Denis Cave, has over the past five years. Researchers have used several data techniques, well-established and state-of-the-art, and statistical techniques to date thousands of items in place, allowing them to compile the most precise and accurate timeline at the date of human work in Denis Caves.
The first study, led by Zenobie Jacobs and Richard Roberts of the University of Wollongong, Australia, introduced new dates for depositing sediments in Denis Cave. To date, these bearings, and then bones and artifacts inside, use researchers a relatively new technique called stimulated luminescence, in which scientists can lastly say that mineral grains such as quartz have been exposed to sunlight. Dozens of sediments were provided in a 280,000-year-old cave.
The results of this work showed that the Denizs first captured the cave about 287,000 years ago and continued to live in the cave some 55,000 years ago. The Neanderthal arrived in the cave some 193,000 years ago, and they continued to live there 97,000 years ago – an overlap of 96,000 years. Bones of 27 animals, including mammals and fish, along with 72 plant species were also analyzed, indicating the variable climate in the region during the millennium of cave occupation. Sometimes this region was quite warm, it was a wood of deciduous trees, but at other times it was a rough and desolate tundra-step habitat.
The main consequence of the Jacobs and Roberts studies is the suggestion that the Denis and the Neanderthals climb together into the cave. It is now possible that these two species do not share space at the same time, but recent evidence suggests that they probably led. In a stunning discovery last year, a group of scientists, some of whom are co-authors of this new study, uncovered the genetic evidence of a hybrid archaic hominin called Denis II, who lived in a cave 90,000 years ago – a girl with Denis Dad and a Neanderthal mum.
This evidence, along with other research directions, suggests that these two species are regularly spoken and that this was not only a singular case.
The second study, led by Katerina Douka of Max Planck's Institute for Human History in Germany, offered new data for the Neanderthal and Denisovan fossils, along with the teeth and bone pendants found in the site. Douk's team used several techniques to indirectly and directly deliver thousands of bone fragments and artifacts, including radiocarbon dating and dating of uranium series, both utilizing known rates of radioactive decay.
"It's the first time we've been able to confine the age to all the archaeological sequences of the cave and its contents," said Tom Higham, an archaeologist at Oxford University and a co-author of a new study.
The oldest Denisovan fossil suggests that this group was present on site fifty thousand years ago, while all non-Afghan fossils including Denis II. They were dated 80,000 to 140,000 years ago. The youngest denizen fossils were dated 52,000 to 76,000 years ago.
"Paper Douka is exciting because we knew that Neanderthals and Denis used Denis Cave and that both groups were here or close but we did not know too much about the time each group visited the cave or the time the two groups overlap at using the cave, "said Sharon Browning, a research professor at Washington University's biostatistics department, who did not participate in the new study for Gizmodo.
Many of the data provided in the Douka document had large margin of error, as a result of complex stratigraphy (for example, the concern that some items were cast on lower stratigraphic layers) and unwilling to go beyond the available data. But while there is "considerable uncertainty in some estimates and the possibility of visits to both groups that were sooner or later but did not leave a trace found," Browning said these results still "helps determine the likely way to use time."
Artifacts found on the site, such as skeletal dots, pierced teeth, and pendants, were dated 49,000 to 43,000 years ago, and today are the oldest artifacts discovered in the northern part of Eurasia. The problem is that these dates are thousands of years after the last evidence of human occupation appeared in the cave.
"Based on current archaeological evidence, it can be assumed that these artifacts are associated with the Denis population," the authors of the study argue. "At present, it is not possible to determine whether anatomically modern humans are involved in their production, as the fossil and genetic evidence of a modern man of such ancestry has not yet been identified in the Altai region."
The denizens were probably the producers of these items because this is the simplest explanation given that the Neanderthals have long since left the cave and according to new research there is no evidence of a modern man in the cave. But the anthropologist Chris Stringer of the UK's Natural Science Museum is not convinced that these items belonged to the Denizens.
"My money should be on early modern people who can be mapped elsewhere at this time, for example at Ust'-Ishim in Siberia, but the authors of the documentary Duk rather surprisingly claim to be the most parsimonious assumption that Denisovans were responsible, although no one Denis is still known as late, as in the sequence, "Stringer said Gizmodo. "Only other discoveries and other researches can solve this question satisfactorily."
Stringer said he likes two new studies and says "they bring the latest dating techniques to carry stratigraphy, paleoclimatic records and human fossils," but said there are still many unresolved issues. There is, for example, the possibility that some, if not all, bones were dragged into the cave by carnivores who hunted people, said, or that the bones move dramatically over the years from the original resting place, discard dating to a large extent.
"However, in denomination, it seems that Denis may be at least intermittently placed on the spot for about 250,000 years, from nearly 300,000 years ago, about 50,000 years ago, with Neanderthals also there for the period between years," Stringer said. "It seems that the profession is focusing in warmer periods, which reinforces the view that Denis cave was probably on the northern occupation line for both of these populations.
The fact that the Neanderthals and the Denis were both both present greatly complicates the distractions that people are responsible for which elements of archeology – perhaps sedimentary DNA studies – eventually help to better map their presence in the cave. "
These uncertainties and large margin of error are undoubtedly frustrating, but these two documents help to remove many of the ambiguities. As time goes by, we still get a clearer picture of archaic human work in Denis Cave. And damn it, it's sometimes fascinating.[Nature, Nature]