|
Post by Admin on Oct 3, 2022 22:00:25 GMT
The Nobel Prize in Physiology or Medicine has gone to Sweden's Svante Paabo for his work on human evolution. The Prize committee said he achieved the seemingly impossible task of cracking the genetic code of one of our extinct relatives - Neanderthals. He also performed the "sensational" feat of discovering the previously unknown relative - Denisovans. His work helped explore our own evolutionary history and how humans spread around the planet. The Swedish geneticist's work gets to the heart of some of the most fundamental questions - where do we come from and what allowed us, Homo sapiens, to succeed while our relatives went extinct. He was just off to pick his daughter up from a sleepover when he got the call saying he'd won. He told the BBC: "I was very surprised and overwhelmed, I had not expected this."
|
|
|
Post by Admin on Oct 15, 2022 5:32:42 GMT
Modern humans and Neanderthals met—and made love, or at least babies—at some point in prehistory. But how long and exactly where the two species intermingled has been a mystery. Now, a reevaluation of radiocarbon dating at archaeological sites in France and northern Spain indicates that some 40,000 years ago, our ancestors overlapped with Neanderthals in the region for up to 2800 years, sharing not just genes with each other, but potentially culture as well. “The time span is insignificant on a geological scale,” says Antonio Rodríguez-Hidalgo, an archaeologist at the Catalan Institute of Human Paleoecology and Social Evolution who was not involved with the study. “But on a human scale, there is enough time for very interesting things to happen.” Other scientists, however, say the wide margins of error for many of the dates analyzed in the study undercut strong claims about the identities of the inhabitants and whether they indeed overlapped. It’s “a good starting point,” but the conclusions could change based on more accurate dating, says Sahra Talamo, a chemist who directs a radiocarbon laboratory at the University of Bologna. Radiocarbon dating estimates the age of organic objects such as bones and charcoal based on the steady radioactive decay of their carbon-14 isotopes. Scientists have used the method for decades—and they’ve been refining it for just as long. A major revision came in 2020, when radiocarbon scientists announced that a brief reversal of Earth’s magnetic field about 42,000 years ago, known as the Laschamp event, had temporarily supercharged the amount of carbon-14 in the atmosphere. Anything living at the time incorporated extra amounts of the isotope as a result, throwing off modern efforts to radiocarbon date their remains. “It pushed dates that were around 40,000 years further back in time and made things that were older than 43,000 or 44,000 years appear younger in time,” says Igor Djakovic, an archaeology Ph.D. student at Leiden University. That period coincides with a critical era in human history. One major kind of stone tool technology in Europe known as the Châtelperronian industry—consisting of palm-size scrapers and knives and traditionally associated with Neanderthals—was replaced by a kit of more sophisticated tools called the proto-Aurignacian industry, which featured smaller, more precisely worked blades traditionally associated with modern humans. (There is debate, however, over whether either industry was truly exclusive to humans or Neanderthals.) That time span is also when Neanderthals began to disappear from their longstanding European strongholds and modern humans started moving into the continent. Hoping to clarify the dates for sites containing Châtelperronian and proto-Aurignacian artifacts, Djakovic and colleagues reran the radiocarbon analyses performed by other teams representing 17 sites across France and northern Spain. They also recalculated the dates for 10 Neanderthal skeletons from the same range. But this time they applied a recently developed calibration standard known as IntCal20, which accounts for the heightened carbon-14 caused by the Laschamp event. None of the dates changed drastically, but as a whole, the oldest dates shifted a bit younger whereas the youngest dates got a bit older, compressing the estimated ranges. Next, they plotted those refined dates using a statistical approach called optimal linear estimation, which aims to predict when a particular technology may have begun and ended based on the intervals in between the ages of known artifacts. The researchers found that modern human associated proto-Aurignacian tools show up in the region between 42,200 and 42,600 years ago, whereas the Neanderthal-associated Châtelperronian tools disappear about 40,800 to 39,800 years ago. That indicates that the two toolmaking industries overlapped in time and space for anywhere from 1400 to 2800 years, the team concludes today in Scientific Reports. The dates—though based on a relatively small number of sites—also suggest proto-Aurignacian tools spread from south to north over time, hinting at the possible route of modern humans through the continent, Djakovic says. It's not the first time researchers have proposed modern humans and Neanderthals overlapped in Europe during this period. But the revised dates offer a narrower, more geographically constrained window into one such possible event, Djakovic says. This overlap would have still provided time for generations of humans and Neanderthals to meet, interbreed, and share toolmaking tips with one another. And that in turn could explain why later Châtelperronian tool caches appear to borrow proto-Aurignacian elements, such as small, precisely made blades, Djakovic says. Still, he admits such interpretations are speculative and controversial. Except for in the small number of instances in which modern human or Neanderthal remains have been found alongside these tools, no one knows for certain which species made which tools at most sites. The study’s agnosticism over which species made the tools is actually a strength, says Emmanuel Discamps, an archaeologist at CNRS, the French national research agency. “Who knows if the Châtelperronian or the proto-Aurignacian were made by Neanderthals, modern humans, hybrids, or a bit of all of that, depending on chronology and geography,” he says. By not assuming the identities of these toolmakers, he adds, researchers can envision more complex histories that might better match what really happened. But the uncertainties in the radiocarbon record still give Shara Bailey, a paleoanthropologist at New York University, pause. Radiocarbon dates are only reliable out to about 50,000 years ago. Dates measured toward the end of that range tend to have large margins of error, she says, making it difficult to make firm conclusions about which objects are older than others. “I take the results of all these types of studies with a grain of salt.” Katerina Douka, an archaeologist at the University of Vienna who helped collect some of the radiocarbon dates reanalyzed in the new study, says it’s great to see her team’s data reused to refine our understanding of when and where Neanderthals and modern humans may have lived side by side. “Western Europe is a cul-de-sac, and many have predicted that this could be a region where the two populations coexisted and interacted more intensely.” But she suspects that in other parts of Europe, such overlaps between different human species and cultures may have been even more complex, and happened at different times and tempos, than the new paper suggests. “There is a lot more to find out about this key period in human evolution.”
|
|
|
Post by Admin on Oct 28, 2022 4:41:52 GMT
Optimal linear estimation models predict 1400–2900 years of overlap between Homo sapiens and Neandertals prior to their disappearance from France and northern Spain Igor Djakovic, Alastair Key & Marie Soressi Scientific Reports volume 12, Article number: 15000 (2022)
Abstract Recent fossil discoveries suggest that Neandertals and Homo sapiens may have co-existed in Europe for as long as 5 to 6000 years. Yet, evidence for their contemporaneity at any regional scale remains highly elusive. In France and northern Spain, a region which features some of the latest directly-dated Neandertals in Europe, Protoaurignacian assemblages attributed to Homo sapiens appear to ‘replace’ Neandertal-associated Châtelperronian assemblages. Using the earliest and latest known occurrences as starting points, Bayesian modelling has provided indication that these occupations may in fact have been partly contemporaneous. The reality, however, is that we are unlikely to ever identify the ‘first’ or ‘last’ appearance of a species or cultural tradition in the archaeological and fossil record. Here, we use optimal linear estimation modelling to estimate the first appearance date of Homo sapiens and the extinction date of Neandertals in France and northern Spain by statistically inferring these ‘missing’ portions of the Protoaurignacian and Châtelperronian archaeological records. Additionally, we estimate the extinction date of Neandertals in this region using a dataset of directly-dated Neandertal fossil remains. Our total dataset consists of sixty-six modernly produced radiocarbon determinations which we recalibrated using the newest calibration curve (IntCal20) to produce updated age ranges. The results suggest that the onset of the Homo sapiens occupation of this region likely preceded the extinction of Neandertals and the Châtelperronian by up to 1400–2900 years. This reaffirms the Bayesian-derived duration of co-existence between these groups during the initial Upper Palaeolithic of this region using a novel independent method, and indicates that our understanding of the timing of these occupations may not be suffering from substantial gaps in the record. Whether or not this co-existence featured some form of direct interaction, however, remains to be resolved.
Introduction Between 40 and 50,000 years ago (kya cal BP), the demographic landscape of Europe is transformed as Neandertals are replaced by anatomically modern humans (AMH) and disappear from the fossil record1. Recent evidence from Bulgaria, the Czech Republic, and south-eastern France indicates that the first AMH arrived in Europe by at least 47–45 kya cal BP—and possibly as far as ~ 54 kya cal BP2,3,4. At a continental scale, this would suggest a possible overlap of upwards of 14,000 years between these human species3. Yet, little is known about the nature, timing, and specific geographic areas of interaction between Neandertals and Homo sapiens during this critical period in human evolutionary history. For example, genetic data has shown there to be notable variation in the presence of recent Neandertal ancestry in early AMHs in Europe3,5,6,7 and—although the sample size is limited—it is interesting to note that no late European Neandertals have yet exhibited evidence of a recent modern human ancestor8. One possible explanation for this pattern is that, at least in some regions, the first AMHs to colonise Europe may not have directly encountered Neandertals.
Archaeologically, the first part of this period—the Middle to Upper Palaeolithic transition—is characterised by so-called ‘Initial Upper Palaeolithic’ assemblages (e.g. Bacho Kiro) which are increasingly interpreted as representing an initial, possibly unsuccessful migration of AMH into Europe occurring around 47–44 kya cal BP3,7,9. The term ‘unsuccessful’ has been used as these initial groups appear to have left no visible genetic contributions to present-day populations in Europe3,7. Recently published evidence from Grotte Mandrin, south-eastern France, may however extend this initial migration to as far back as ~ 54,000 years ago10. At this site, a deciduous molar attributed to Homo sapiens was recovered from an archaeological layer bearing a distinctive IUP-type stone tool industry and dating to somewhere between 58 and 51,000 years ago (ibid.). If confirmed with additional evidence, this would constitute a significant shift in perspective—placing AMHs in far western Europe upwards of 12,000 years earlier than previously thought. Interestingly, there is no evidence of AMH occupation in any region of France for upwards of 12–14,000 years following the disappearance of the Neronian industry—which in fact seems to represent a brief, geographically restricted technological entity10,11. Instead, until ~ 42,000 years ago, the archaeological record of France appears to be characterised exclusively by Neandertal remains and cultural material. The evidence from Grotte Mandrin may in fact lend strength to the idea that this initial period of AMH presence in Europe consisted primarily of small scale, unsuccessful migrations—without persistent co-existence between incoming AMHs and Neandertals.
The onset of the Aurignacian complex (sensu lato) across Europe at around 42 kya cal BP is widely accepted as reflecting a second, more successful migration of AMH groups into Europe’s western extensions, and may signal the first major and persistent phase of European colonisation by our species9,12. In many regions, Protoaurignacian and Early Aurignacian assemblages appear to rapidly replace so-called ‘transitional’ stone tool industries (e.g. Uluzzian, Châtelperronian, Lincombian-Ranisian-Jerzmanowician), some of which are considered to be products of Neandertals. Here, we use the term ‘transitional’ as a communicative tool, since the nomenclature has been widely used to categorise this particular group of techno-complexes (e.g. Hublin9). However, to take the Châtelperronian as an example, the ‘transitional’ moniker is in reality misleading. The term was originally intended to describe stone tool industries showing a mixture of Middle and Upper Palaeolithic typo-technological features (e.g. presence of both MP and UP retouched tool forms). However, extensive research over the past two decades has established that the Châtelperronian represents an entirely ‘Upper Palaeolithic’ stone tool industry and should not continue to be listed as ‘transitional’ in the original sense of the term13,14,15,16,17.
At present, the Châtelperronian industry of France and northern Spain shows the strongest association between one of Europe’s ‘transitional’ industries and Neandertal fossil remains. Neandertal remains have been recovered from stratigraphic layers containing Châtelperronian artefacts at the two key French sites of Saint-Césaire and Grotte du Renne18,19,20,21,22. However, the validity of these associations is heavily debated, and consensus regarding both the makers of this industry and the reliability of the Neandertal associations is not unanimous13,23,24. Nonetheless, despite ongoing discussion, a Neandertal authorship for this industry remains the most parsimonious and well-accepted model. The principle reason for this is that, debates aside, the only human remains to as of yet be recovered from stratigraphic layers containing Châtelperronian artefacts are those of Neandertals.
Technological similarities between some Châtelperronian and Protoaurignacian assemblages (i.e. blade and bladelet-based lithic technology, bone tools, and personal ornaments)15,16,20,25,26 has led to discussion concerning the potential interactions between Homo sapiens and Neandertals in this region prior to the latter’s disappearance around 40 kya cal BP1,9,15,16,20,27,28,29,30. Most notably, it has been proposed that the ‘Upper Palaeolithic’ character of Châtelperronian assemblages reflects the influence of allochthonous AMHs producing Protoaurignacian assemblages onto local Neandertal populations. However, whenever these two lithic industries are identified at the same site, Protoaurignacian assemblages are always located stratigraphically above Châtelperronian assemblages15. In combination with chronological data suggesting an earlier ‘start’ date for the Châtelperronian, the initial ‘emergence’ of this industry appears to be causally unrelated to the (later) appearance of the Protoaurignacian. This does not, however, preclude the partial contemporaneity of these occupations at some point in time. One of the most well accepted, although debated, hypotheses for the origin of the Châtelperronian is a local development from a regional Mousterian substrate13,15,24,31. The modern iteration of the model posits that some form of contact/interaction with groups producing Protoaurignacian technology would have later triggered the development of more ‘Upper Palaeolithic’ characteristics within the Châtelperronian (for example, retouched bladelets resembling the Dufour-type)15,16. Bayesian modelling of radiocarbon ages for Protoaurignacian and Châtelperronian assemblages in this region has already indicated that these occupations may have co-existed for upwards of 1600 years39.
From a methodological perspective, two recent developments in the dating of archaeological phenomena are relevant to these discussions. The first concerns improvements to the calibration curve used to convert C14 measurements into reliable calendar dates32. The recently operationalised IntCal20 radiocarbon calibration curve has significant implications for the chronology of the initial stages of the Upper Palaeolithic in Europe33. Specifically, the identification of a radiocarbon time-dilation during the 48 to 40 kya cal BP time window—during which the radiocarbon clock appears to have run almost twice as fast as it should—has led to the suggestion that the European transition from Neandertals to AMHs may have been a more compressed process which took place slightly earlier than previously thought (Fig. 1) (ibid.). This expanded C14 time scale was not accounted for in former calibration curves, and is thought to be related to a significant rise in atmospheric 14C production (on the order of as much as a 700% increase) linked to the transition into the Laschamp geomagnetic excursion, which reached its peak around 43–41 kya cal BP32.
|
|
|
Post by Admin on Nov 1, 2022 5:53:45 GMT
Figure 1 The effects of the recently operationalised IntCal20 radiocarbon calibration curve on C14 measurements produced for human remains between 50 and 37 kya (bottom)—compared with both the uncalibrated measurements (top) and the ages obtained using the previous generation curve (IntCal13, middle) (redrawn and adapted with permission after Bard et al., 2020). Note the 'time-dilation' causing a compression of dates centred around the 43–42 kya cal BP mark (black arrows). 1—Les Rochers-de-Villeneuve (France), 2—Vindija Cave Vi-33.26 (Croatia), 3—Bacho Kiro (Bulgaria), 4—Ust’-Ishim (Siberia), 5—Bacho Kiro (Bulgaria), 6—Goyet Q57-1 (Belgium), 7—Goyet Q305-4 (Belgium), 8—Bacho Kiro (Bulgaria), 9—Neander Valley NN4 (Germany), 10—Neander Valley Nean 1 (Germany), 11—Les Cottés Z4-1514 (France), 12—Goyet Q53-4 (Belgium), 13—Neander Valley NN1 (Germany), 14—Goyet Q376-1 (Belgium), 15—Goyet Q56-1 (Belgium), 16—Goyet Q55-1 (Belgium), 17—Bacho Kiro (Bulgaria), 18—Grotte du Renne AR-14 (France), 19—Saint-Césaire (France), 20—Spy 737a (Belgium), 21—Tianyuan Cave (China), 22—Pestera cu Oase (Romania). Figure was produced using Adobe Illustrator. The second methodological development is the recent introduction of optimal linear estimation (OLE) modelling to archaeology from palaeontological and conservation sciences34. OLE is a frequentist modelling approach that can reconstruct the full chronology of cultural and biological phenomena by statistically inferring origin (‘origination’) and end (‘extinction’) dates. Unlike traditional estimates which often use the earliest or latest known dated artefacts/fossils as a start or end point, OLE is able to infer how much longer a phenomenon is likely to have persisted prior to, or after, these known occurrences. In general terms, this method is underpinned by the assumption that we rarely, if ever, find the ‘first’ or ‘last’ occurrence of a species, artefact, or cultural tradition35,36 Meaning that the earliest and latest instances of a given archaeological (or fossil) phenomenon are unlikely to ever be discovered and dated. OLE addresses this issue by using the temporal spacing of known artefact discoveries to statistically estimate the portion of the archaeological record that has not yet been, or is not able to be, discovered34,37. In turn, providing a more accurate account of a phenomenon’s temporal presence. These developments have potential to improve our understanding concerning the co-existence of AMHs and Neandertals during the Middle to Upper Palaeolithic transition, preceding the disappearance of the latter. In particular, despite co-existence between Neandertals and AMHs being established at a continental scale, convincing evidence of co-existence at any kind of regional scale remains highly elusive. Of particular interest here is France and northern Spain, a region which features four Neandertal fossils directly-dated to between 44 and 40 kya cal BP8,22,38,39, numerous well-studied and reliably dated Châtelperronian assemblages associated with late Neandertals1,38,40,41,42, and some of the earliest well-dated Protoaurignacian contexts within western Europe43,44,45,46,47. Here, we use the recently operationalised IntCal20 calibration curve to recalibrate a large selection of modernly produced C14 determinations for Châtelperronian assemblages, Protoaurignacian assemblages, and directly-dated late Neandertals from France, northern Spain, and Belgium. Then, we analyse these updated age ranges using OLE modelling to statistically infer the ‘origination’ date of anatomically modern humans and the extinction date of Neandertals in this region. As highlighted earlier, this method uses the temporal spacing of known occurrences to statistically estimate the portions of the record that have not yet been, or are not able to be, discovered (i.e. the ‘first’ and ‘last’ occurrences). OLE has never before been applied to investigate the temporal overlap of Palaeolithic traditions. Finally, we compare the results of this approach with Bayesian models which rely on known dated occurrences as the ‘first’ and ‘last’ datapoints. By doing so, we contribute new estimates and evaluate the reliability of previous estimates for the duration of overlap between Neandertals and Homo sapiens in this key region of western Europe.
|
|
|
Post by Admin on Nov 7, 2022 21:35:39 GMT
Results The dataset consists of fifty-six uncalibrated radiocarbon age determinations from Châtelperronian and Protoaurignacian assemblages (n = 28 and 28) from seven and ten archaeological sites, respectively. Collectively, covering northern Spain and south-west, central and Mediterranean France (Supplementary Table S1, Supplementary Fig. S1). In addition, to examine the temporal relationship of Neandertal fossils with these assemblages, we included all available radiocarbon estimations from directly-dated late (< 50 kya cal BP) Neandertal specimens within the surrounding region (France n = 4, Belgium n = 6, total n = 10) (Supplementary Table S1). In total, sixty-six radiocarbon age determinations from eighteen discrete, well-established archaeological sites are represented within the dataset (Supplementary Table S1). A detailed summary of the samples used here and the OxCal scripts used in the analysis, along with all accompanying information, is made available in full (Supplementary Dataset S1, Supplementary Fig. S8).
Chrono-spatial patterning of known Châtelperronian, Protoaurignacian, and directly-dated Neandertal occurrences in the region The plots summarising the distribution of the aggregated IntCal20 calibrated radiocarbon ages (at 95.4% confidence) for the Châtelperronian, Protoaurignacian, and directly-dated Neandertal datasets are illustrated in Fig. 2—including Bayesian start/end dates produced using the same datasets. The probability distributions show clear overlap between all three categories. Based on the aggregated datasets (Supplementary Dataset S1, Supplementary Figs. S2–S4), Bayesian modelling suggests a start date for to Châtelperronian between 45,343 and 44,248 kya cal BP, and an end date between 41,081 and 40,138 kya cal BP. The dataset for the regional Protoaurignacian produces a modelled start date between 42,873 and 41,747 kya cal BP, and an end date between 39,197 and 38,087 kya cal BP. For the directly-dated Neandertal dataset, the modelled end date for Neandertal presence in this region is predicted to have occurred between 41,757 and 39,859 kya cal BP. Taken together, the chronological data for the regional Protoaurignacian, Châtelperronian, and directly-dated Neandertals show a partial overlap. For example, calibrated age ranges produced for the Protoaurignacian assemblages at Isturitz (n = 4), Labeko Koba (n = 2), Gatzarria (n = 1), Esquicho-Grapaou (n = 1), and L’Arbreda (n = 4) overlap either entirely or near-entirely with three directly-dated Neandertals from France—Saint-Césaire (42,206–39,960 cal BP, IntCal20), La Ferrassie (LF8, 41,696–40,827 cal BP, IntCal20), and Grotte du Renne (AR-14, 42,370–40,778, IntCal20).
|
|