john hawks weblog

paleoanthropology, genetics and evolution

Spain

  • Blombos pigment workshop

    Fri, 2011-10-14 02:23 -- John Hawks

    I know that some readers are starting to wonder if I've forgotten about paleoanthropology lately. Let's just say that the Neandertal and Denisova genomes have me very busy, and I don't think you'd want it any other way.

    But on the paleoanthropological front, Science has released a paper by Chris Henshilwood and colleagues [1] describing two toolkits used by ancient MSA people more than 100,000 years ago to grind pigment and mix it with animal fat, presumably for painting.

    I want to share a picture from the article (credit G. Moéll Pedersen), which shows one of the two toolkits in situ. I want to make a point about it that would be difficult without seeing the photo:

    That photo shows Tk1, the first toolkit. Now, here's the description of what Henshilwood and colleagues were able to interpret from the artifacts in the photo:

    We infer that manufacturing proceeded as follows: Pieces of ochre (FS1 and FS2) were rubbed on quartzite slabs to produce a fine red powder, and some were knapped with large lithic flakes. The ochre chips resulting from the latter were crushed with quartz, quartzite, and silcrete hammerstones/grinders. Quartzite grinders were used to crush goethite or hematite-rich lutite. Medium-sized mammal bone was crushed, probably with a stone hammer. The red or reddish brown color and cracked, flaky texture of some of the trabecular bone suggest that it was heated before crushing, probably to enhance the extraction of the marrow fat. The hematite powder, charcoal, crushed trabecular bone, stone chips, and quartz grains and a liquid were then introduced into the Haliotis shells and gently stirred (figs. S5, S25, and S26). Charcoal is rare in the layer-CP matrix, suggesting that it was a deliberate addition to the mix. The quartz and quartzite chips, produced during the action of crushing the ochre, and the quartz grains may have been incidentally incorporated.

    You can see how the complex interpretation was made possible by finding these things in association as part of one feature. If one or two of these pieces had been found separately, many archaeologists would be skeptical of such a story. Indeed, even the interpretation of this toolkit might appear incredible were it not for the second toolkit also found at the site. Archaeologists are conservative that way, they don't like to overinterpret the evidence. Even this series of events -- grinding, heating, mixing, and so on -- isn't very complicated compared to many activities that humans do every day. It's an example where Henshilwood and colleagues have advanced what archaeologically can show beyond a shadow of doubt about ancient people, but still leaves a gap in our understanding of the ancient cultural system.

    A complex behavioral pattern that is actually found cannot have been an isolated instance. Complexity implies a tradition of which these toolkits are only miniscule remnants.

    In this light, I should point out that the Blombos evidence is by far earlier than other evidence of pigment grinding and heating, but not unique in the South African MSA. Last year I linked to a Jennifer Viegas story about red ochre production at Sibudu Cave, South Africa. This is Lyn Wadley's work [2], and the research paper has since been published in the Journal of Archaeological Science. Also in that journal last year was a paper by Francesco d'Errico and colleagues [3], which described pigment nodules found in the Middle Paleolithic in Mt. Carmel site of Skhul, Israel. We have quite a lot of circumstantial evidence about pigment use in these early contexts both inside and outside Africa, and more is building all the time.

    The archaeological record is bad in many ways. The wooden artifacts preserved at Abric Romani, Spain, are another example of an exceptional archaeological find. I've been meaning to write about them since Julien Riel-Salvatore mentioned them last month. Archaeologists have been working the Middle Paleolithic for nearly 150 years, yet we know next to nothing about wooden artifacts. Abric Romani is not entirely alone, but is enough to show the existence of a broader tradition occupying this blind spot, because the extensive shaping of artifacts and labor used to create them implies a cultural knowledge and utility.

    References

    1. Henshilwood CS, d'Errico F, van Niekerk KL, Coquinot Y, Jacobs Z, Lauritzen S-E, Menu M, and Garcia-Moreno R. 2011. A 100,000-Year-Old Ochre-Processing Workshop at Blombos Cave, South Africa. Science 334:219 - 222.
    2. Wadley L. 2010. Cemented ash as a receptacle or work surface for ochre powder production at Sibudu, South Africa, 58,000 years ago. Journal of Archaeological Science [Internet] 37:2397–2406. Available from: http://dx.doi.org/10.1016/j.jas.2010.04.012
    3. D'Errico F, Salomon H, Vignaud C, and Stringer C. 2010. Pigments from the Middle Palaeolithic levels of Es-Skhul (Mount Carmel, Israel). Journal of Archaeological Science [Internet] 37:3099–3110. Available from: http://dx.doi.org/10.1016/j.jas.2010.07.011
    Tags: 
    wood
    art
    art in science
    Blombos
    South Africa
    Abric Romani
    Spain
    Europe
    MSA
    Synopsis: 
    Complex toolkits from Blombos, South Africa, show pigment processing before 100,000 years ago.

  • Neandertal band of brothers

    Tue, 2010-12-21 11:48 -- John Hawks

    Carles Lalueza-Fox and colleagues [1] have a new analysis of the mitochondrial DNA from El Sidrón, Spain. The site has a minimum number of 12 Neandertal specimens, dating to 49,000 years ago. The authors recovered mtDNA from all of the skeletal individuals, and additionally tested for the presence of Y chromosome to diagnose sex.

    They found that all the adult males in the sample are close maternal relatives -- that is, they all share a single mtDNA haplotype. In contrast, the adult females and juveniles have a range of different haplotypes. Using some conclusions about the archaeological context (discussed below), they interpret the 12 individuals as part (possibly all) of a kin-structured group. They note that the relationships are then consistent with a patrilocal residence pattern: The men in the group are linked by kinship, the women have come from other kin networks, possibly transferred from other groups.

    In the last paragraph of the paper, the authors suggest a further conclusion about life history:

    Based on the ages of the El Sidrón group members and their mtDNA lineages, we speculate that juvenile 2 is the offspring (or close matrilineal relative) of female adult 5 and that juvenile 1 and the infant are the offspring of female adult 4. If correct, the latter relationship would indicate an interbirth interval of around 3 y for Neandertals. This period fits with the average 3-4-y interbirth interval reported for several modern hunter-gatherer groups (19).

    That conclusion would be based on a single birth interval. It depends on the assumption that these juveniles are in fact siblings, which further depends on the proposed site deposition scenario. So although it is consistent with the data, I think it is very weak evidence. Still, it's a lot more evidence that I expected to have anytime soon. Moreover, it seems to me that the birth interval is testable with reference to dental development. A 3-4 year birth interval implies weaning in or before the fourth year of life, which ought to be reflected in enamel formation.

    Awesome! We can now test hypotheses about Neandertal social organization directly from DNA evidence. The authors' hypothesis about patrilocality is consistent with the mtDNA, and I think it is likely to be the correct one.

    Still, we have many reasons to be cautious about the interpretation. For one thing, Neandertals are already known to be relatively low in mtDNA variation, with very little regional population structure in the mtDNA. In such a population, it wouldn't be surprising to find individuals sharing the same mtDNA haplotype, even if they were not close kin. It might seem surprising that the individuals sharing the mtDNA haplotype are all men, but with a sample of only 12 individuals, that coincidence isn't really all that unlikely. The limited mtDNA variation would then be a sign of inbreeding at a regional level, not necessarily the kin structure of a particular group at a particular time.

    Placing those individuals together as part of the same group is a forensic challenge. For most bones at archaeological sites, we would assume that the individuals lived at different times, possibly hundreds or thousands of years apart. The interpretation that they represent a single group requires several assumptions about the deposition of the remains, which amount to a detailed and surprising scenario. Lalueza-Fox and colleagues describe the El Sidrón skeletal assemblage as a result of systematic cannibalism:

    The excavations to date have yielded > 1,800 hominin skeletal fragments and ∼400 Mousterian stone tools made in situ (3), but faunal remains are very scarce. The Neandertal bones are in a secondary position, and the original deposit, worn out by erosion, is thought to have been placed either on the surface or in an upper karst level (2). The present assemblage occurred shortly after the death of the individuals by the collapse of an upper gallery into the Ossuary Gallery triggered by a natural event, probably a violent storm that also dragged down pebbles and clay (Fig. S1). Given that (i) ≈18% of the lithic industry can be refitted, and (ii) the widespread spatial distribution of these refitted artifacts, it may be surmised that they result from a single and brief cultural activity. This likelihood lends even more support to the synchrony of the whole assemblage (2, 3), dating to around 49,000 y ago (4). Some evidence, such as skeletal parts still in anatomical articulation, indicates little site disturbance since formation. Ex hypothesis, the fact that all types of skeletal remains show evidence of anthropic activities associated to cannibalism (2) could indicate that the assemblage corresponds to a Neandertal group processed by other Neandertals on the surface. Although it is impossible to be sure that the individuals represent a contemporaneous group, alternative explanations, such as recurrent accumulation over time of cannibalized individuals that were closely related through the female line, seem less plausible.

    If this interpretation is correct, it would be the most stunning example of intergroup violence known from the Pleistocene. Imagine the circumstance in which a group of hunter-gatherers would kill and butcher 12 individuals in one paroxysm of aggression. Certainly it was not mere survival, it was warfare.

    Is it true? The problem is the "violent storm". How do we know that the existing assemblage is a good representation of the original deposition site? The high number of refits does imply that we're not looking at a random sample of an originally much larger assemblage, but it's hard to be more definitive. If we have the remains of 12 individuals, how many may have been involved in the act?

    Naturally, if the remains had actually accumulated over a longer time, the conclusions about patrilocality would be unwarranted. In that case we would be back to a more general question of regional or local inbreeding among Neandertals, interesting from the point of view of population structure, but with less concrete information about social organization.

    The forensic case provides a window into behavior that is potentially much broader. Krapina is another site with hundreds of skeletal fragments representing an even larger number of individuals, which may also represent one or more instances of cannibalism. In that case, the debate about cannibalism (versus secondary reburial of defleshed bones) has flared off and on for years. It is just very difficult to attain a reasonable certainty about such behaviors from the archaeological and skeletal evidence at hand.

    I will be interested to read more about the context at El Sidrón as the research continues. The issues of kinship can be easily settled with nuclear DNA sequencing, and should in fact lead to some extremely interesting science, if that can be accomplished. The authors list some of the barriers to such sequencing, given a relatively low DNA yield in many of the specimens, but the field has rapidly progressed. Meanwhile, the archaeological interpretation of the site may allow us to revisit some other Neandertal assemblages, looking for other signs of aggression, violence, and social organization.

    References

    1. Lalueza-Fox C, Rosas A, Estalrrich A, Gigli E, Campos PF, Garcia-Tabernero A, Garcia-Vargas S, Sánchez-Quinto F, Ramirez O, Civit S, et al. 2011. Genetic evidence for patrilocal mating behavior among Neandertal groups. Proceedings of the National Academy of Sciences [Internet]. Available from: http://dx.doi.org/10.1073/pnas.1011553108
    Tags: 
    Europe
    El Sidron
    social networks
    forensics
    Neandertals
    Middle Paleolithic
    Spain
    social dynamics
    Neandertal DNA
    cannibalism
    Synopsis: 
    Analysis of mtDNA from El Sidron cave shows relationships among the males, presumed to be an ancient group.

  • Just ducky

    Mon, 2009-12-07 10:42 -- John Hawks

    A week or two ago, I was pointed by a press release to some recent research from Bolomor Cave, Spain, where the levels occupied by early/pre-Neandertals have been yielding interesting evidence about diet breadth. The pointer was about "bird consumption", but in this case the birds are all ducks -- genus Aythya, which includes living canvasbacks, for you duck hunters out there. The reference is a newish paper in Journal of Archaeological Science by Ruth Blasco and Josep Fernández Peris.

    Something like 155,000 years ago, some hominins brought 8 ducks into the cave, cut them up (leaving cutmarks) and roasted some of them (leaving bone with burned and charred ends where the meat isn't).

    Not so terribly surprising, but then we don't have a lot of sites of equivalent age where there's good evidence of repeated bird consumption. The cave also has a lot of rabbit bones, and some tortoises.

    Blasco (2008) described the evidence for tortoise consumption from a somewhat later level of the cave (Level IV), dating to before 121,000 years ago. That paper included the gruesome work of identifying human toothmarks that gnawed off the ends of several of the long bones. They also roasted some of the tortoises, apparently before disarticulation.

    What I found an interesting element of both papers was the close analysis of the application of fire in the processing of the remains. Naturally from this distance in time it isn't possible to discover everything. But together with experimental archaeology and taphonomy, it may be possible in many cases to test for the presence of ethnographically-attested models of butchering, cooking, and post-consumption processing of the remains.

    This means that where the record is good, you can also test for the absence of such behaviors. I was reminded last week that I haven't yet posted my review of Richard Wrangham's book, Catching Fire. In light of several requests, I'm buffing off the rough edges now and I'll post it later this week. When it comes to testing Wrangham's hypothesis -- in brief, that "cooking made us human" -- it is precisely the kind of close archaeological work pursued in these papers that is necessary.

    Which makes it interesting that, in these rather recent archaeological levels with clear evidence of cooking, there is good evidence that several of the ducks and tortoises weren't cooked before humans ate them.

    References:

    Blasco R. 2008. Human consumption of tortoises at Level IV of Bolomor Cave (Valencia, Spain). J Archaeol Sci 2839-2848. doi:10.1016/j.jas.2008.05.013

    Blasco R, Fernández Peris J. 2009. Middle Pleistocene bird consumption at Level XI of Bolomor Cave (Valencia, Spain). J Archaeol Sci 36:2213-2223. doi:10.1016/j.jas.2009.06.006

    Tags: 
    Middle Pleistocene
    Europe
    hunting
    Middle Paleolithic
    archaeology
    Spain
    diet

  • Sima species

    Fri, 2009-10-09 14:49 -- John Hawks

    Michael Balter has a nice Science writeup of the recent Gibraltar conference, "Human Evolution 150 Years After Darwin."

    A hush fell over the room as Tattersall sat down and Arsuaga got up to speak. To nearly everyone's surprise, Arsuaga agreed that the Sima de los Huesos skulls looked nothing like other H. heidelbergensis specimens. Nor, he said, do 13 other skulls his team had recently excavated there. "We have always said that we put the Sima hominins under the H. heidelbergensis umbrella for convenience, for practical reasons," Arsuaga said, adding that his team agrees with Tattersall that the accretion scenario is not likely. But he resisted Tattersall's call to rename the Sima fossils, at least until the remaining 13 skulls are published in coming months.

    Below that, Jean-Jacques Hublin shows he's a lumper not a splitter.

    References:

    Balter M. 2009. New Work May Complicate History Of Neandertals and H. sapiens. Science 326:224-225. doi:10.1126/science.326_224

    Tags: 
    Middle Pleistocene
    Homo heidelbergensis
    Spain
    Europe
    Neandertals
    Atapuerca

  • Neandertals, plants, and fish

    Fri, 2009-09-18 08:30 -- John Hawks

    I don't read Spanish well, but I'm going to go ahead and link a news article in a Spanish journal about Neandertal diet and cooking at the Spanish site of El Salt:

    Uno de los casos es la aplicación de la química orgánica en el estudio de la estructura de combustión, conocida como el lugar en donde los neandertales hacían las hogueras para calentarse o cocinar. Ahora "estamos empezando a saber que asaban animales como el ciervo y la cabra", señala Galván. Han tenido conocimiento de esta información a través "de las grasas contenidas en las piedras quemadas procedentes del asado de estos animales", dijo la doctora. Asimismo, también han encontrado grasas de origen vegetal y restos de "espinas de peces quemadas". Y es que los neardentales sabían utilizar todas las materias primas que tenían a su alcance.

    One example [of a "quantum leap" in excavation techniques] is the application of organic chemistry to the study of hearths, used by the Neandertals for heat or cooking. Now "we are learning that they roasted animals like deer and goats," said [Bertila] Galvan. This information was obtained from "the fat contained in burned rocks from cooking these animals," said the doctor. In the same way, they also found fats of vegetal origin and remains of "burned fish bones." And that shows that the Neandertals knew how to use all the raw materials available to them.

    Not much more than that, but I think it's very interesting in light of last week's story about flax fibers. The point is that these microscopic and chemical excavation techniques are able to find some surprising information -- a process in archaeology that is mirroring the application of similar techniques to dinosaurs. Results like these show the great promise of such analysis, or the reanalysis of existing samples. It seems like a very propitious time to be trained in chemical techniques to apply to archaeological sites.

    Julien Riel-Salvatore has a little bit of context, Anthropology.net has more, and Martín Cagliani has the most direct discussion, although that does raise the Spanish language problem again!

    I'll be waiting for confirmation from other reports from this site, and hope that we can see some replication.

    Tags: 
    Europe
    Mousterian
    plants
    diet
    Middle Paleolithic
    Neandertals
    Spain

  • The spotty Acheulean

    Wed, 2009-09-02 22:59 -- John Hawks

    Scott and Gibert report in today's Nature on the "oldest handaxes" in Europe:

    In Africa, large cutting tools (hand-axes and bifacial chopping tools) became part of Palaeolithic technology during the Early Pleistocene (1.5 Myr ago). However, in Europe this change had not been documented until the Middle Pleistocene (

    The "Anthro 101" version of the Acheulean makes it out to be a million-year-long technological yawn. The breakthrough of the first handaxes 1.5 million years ago led to a stultifying stasis. The handaxe was a "Paleolithic pocket knife" useful for many purposes -- but the advent of Levallois manufacture around 300,000 years ago consigned the handaxe to the midden of history. Except, of course, for scattered, benighted peoples who were still using handaxes up into historic times -- the exceptions proving the rule of bifaces' never-ending utility.

    Well, the Acheulean was boring, but it wasn't uniform. The Anthro 101 version makes Acheulean people sound too accomplished -- like they invented the bifaces and then started turning them out like industrial robots for a million years.

    Not so: Fine, finished bifaces tend to be less than 500,000 years old. They also tend to be European. Acheulean people didn't usually carry rock very far. With more sources of chert and flint, Europe's geology allowed a wider selection of fine handaxes than Africa's. That is, at least after 500,000 years ago or so. Before then, there just weren't very many handaxes in Europe.

    Here, Scott and Gibert suggest that maybe some other sites with "advanced" or "terminal" Acheulean may prove to be earlier than people now think. The two sites in this study were both initially thought to be much later -- for example:

    The youthful age (200 kyr old) assumed for Solana del Zamborino was largely based on its well-developed Acheulian lithic typology. Such a young age contrasts with our continuing lithostratigraphy and palaeoclimate research in the region, which indicates a final, major lake-forming event near the end of the Early Pleistocene (starting 800 kyr ago) and deposition terminating in the Baza Basin (600 kyr ago).

    They could well be right -- some European sites now thought to be late (post-500 kyr) might be earlier. What does that mean for our understanding of the Acheulean?

    Lower Pleistocene Europeans sometimes made finished bifaces, these were initially sporadic, and later became more and more common until the advent of Middle Paleolithic technocomplexes. The sporadic appearance suggests that people could live without handaxes, and that they were simple enough to be repeatedly invented. There's just not that much information content there, and groups of Early to Middle Pleistocene people arrived at the same solutions again and again.

    Technological "progress" is a misnomer before around 300,000 years ago. Early Homo made Oldowan (and Oldowan-like) industries that required few capabilities not mastered routinely by wild chimpanzees. Some, sure, but few. Bifaces require a bit more: a spatial conception of symmetry, longer action sequences. But Early and Middle Pleistocene people didn't carry it off all the time; they kept losing the biface outside Africa. And they kept hitting that biface mode. Curious.

    Other entries of interest:

    "Early Malaysian axes

    And then there was Levallois

    How monolithic was the Acheulean?

    Acheulean endings

    References:

    Scott GR, Gibert S. 2009. The oldest hand-axes in Europe. Nature 461:82-85. doi:10.1038/nature08214

    Tags: 
    Lower Paleolithic
    Middle Pleistocene
    Spain
    Acheulean
    stone tools
    Europe

  • Not a lasting last for the Neandertals

    Wed, 2006-09-13 17:02 -- John Hawks

    The latest in a long line of "last known Neandertal" sites is now Gorham's Cave, Gibraltar. Of course, if this were actually a continuing string of "latest" sites, you would expect we would eventually either reach the present day, or some mathematical limit. There seems to be little danger of that happening for a while, though, since the previous "last known Neandertal" sites keep turning out to be older than their "first known" radiocarbon dates!

    The current paper by Clive Finlayson and colleagues has a good short review of this issue:

    The sequence of radiocarbon dates presented, including 14 dates at or statistically younger than 30 kyr bp, are the only currently reliable ones that establish the persistence of Neanderthals and associated Mousterian technology after 30 kyr bp. Earlier claims are now dismissed or are uncertain for a variety of reasons and in particular after the revision of dates on bone with the use of ultrafiltration treatment, a treatment only meaningful for dates on bone. Hyaena Den (UK) is now considered older than 30 kyr bp; the Vindija (Croatia) Neanderthals have been re-dated to between 32 and 33 kyr bp or older; Zafarraya (Spain) is now discarded for several reasons; the Mezmaiskaya, Russia, Neanderthal is now dated to at least 36 kyr bp. The single AMS date on Cervus bone for Caldeirão (Portugal) will require revision and is likely, given the result for Hyaena Den of similar age, to be older than 30 kyr bp. Finally, the single 14C date, from Patella shells, from Figueira Brava, Portugal, is not statistically younger than 30 kyr bp (Finlayson et al. 2006, references omitted).

    So are the current radiocarbon dates for Gorham's Cave any better? Or, to put it another way, why exactly should we believe any new claims about recent dates, given the long list of dates that we are now supposed to forget about?

    Now, I'm not an archaeologist, nor am I a geochronologist. So maybe I'm missing something. But look at this figure from the paper (Figure 1c):

    Section from Gorham's Cave, showing points of radiocarbon sampling, Figure 1c from Finlayson et al. (2006).

    Notice sampling points 16, 17, and 20. Those are the key samples for the paper's conclusion:

    Thus, three samples (16, 17 and 20; Fig. 1) came from in situ Mousterian superimposed hearths. These three dates provide a stratigraphic sequence from 24,010 +- 320 to 30,560 +- 720 yr bp. Taken together, all the dates show that Neanderthals occupied the site until 28 kyr bp and possibly as recently as 24 kyr bp. The evidence in support of the 24 kyr bp date is more limited than for 28 kyr bp, which is taken as the latest well-supported occupation date (Finlayson et al. 2006).

    OK, so we have three samples from the same place in the cave, over a short vertical distance, that appear to represent successive occupations over a few-thousand-year interval. The authors interpret conservatively that maybe the 24,000-year date is too young to be Neandertal -- although they don't describe just what makes the evidence "more limited," considering each date is supported by a single radiocarbon sample.

    But look at sample number 11 in the figure. It appears to have been taken from directly above the putative hearths. So why does it have a date of 27,020 +/- 480 years?

    I think we begin to detect why there is "more limited" evidence for the 24,000-year date. It is directly controverted by the sequence.

    Moreover, we have to doubt the 26,000-year date, considering the evident contamination and/or turbation of the sample directly above it.

    Am I saying the Neandertals weren't in this cave after 30,000 years ago? Well, if you look at the samples in the figure, and their locations, almost all the samples taken from the brown zone (layer IV) have dates between 28,000 and 32,000 years BP. But there are several with dates between 26,000 and 23,000 years, and these are mixed in amongst or below earlier dates in the 28,000-30,000 year BP range.

    Please check out the dates yourself: Sample 23 (23,360 BP) is directly below sample 22 (29,720 BP). Sample 9 (26,070 BP) is directly adjacent to sample 10 (28,360 BP). Sample 15 (23,780 BP) appears to be stratigraphically below sample 14 (30,310 BP), although these are more spatially distant. Sample 28 (28,170 BP) is immediately below sample 27 (31,850 BP). Sample 29 (29,210 BP) is directly below sample 25 (31,780 BP). In all cases these discrepancies are outside the reported confidence limits.

    There seems to be clear evidence of widespread movement of material or contamination in this sequence.

    So, does the sheer weight of dates between 32,000 BP and 28,000 BP lead to the conclusion that the cave was occupied by Neandertals during that time range? Maybe so, but I think the paper raises a lot more questions than it answers. I have to think that we'll be hearing about how this date is equivocal or problematic, instead of it being the "latest Neandertal."

    References:

    Brill D. 2006. Neanderthal's last stand. Nature News 13 Sept. 2006. DOI link

    Finlayson C, and 25 others. 2006. Late survival of Neanderthals at the southernmost extreme of Europe. Nature, advanced online publication doi : 10.1038/nature05195

    Pendergast DM. 2000. The problems raised by small charcoal samples for radiocarbon analysis. J Field Archaeol 27:237-239.

    The latest in a long line of "last known Neandertal" sites is now Gorham's Cave, Gibraltar. Of course, if this were actually a continuing string of "latest" sites, you would expect we would eventually either reach the present day, or some mathematical limit. There seems to be little danger of that happening for a while, though, since the previous "last known Neandertal" sites keep turning out to be older than their "first known" radiocarbon dates!

    The current paper by Clive Finlayson and colleagues has a good short review of this issue:

    The sequence of radiocarbon dates presented, including 14 dates at or statistically younger than 30 kyr bp, are the only currently reliable ones that establish the persistence of Neanderthals and associated Mousterian technology after 30 kyr bp. Earlier claims are now dismissed or are uncertain for a variety of reasons and in particular after the revision of dates on bone with the use of ultrafiltration treatment, a treatment only meaningful for dates on bone. Hyaena Den (UK) is now considered older than 30 kyr bp; the Vindija (Croatia) Neanderthals have been re-dated to between 32 and 33 kyr bp or older; Zafarraya (Spain) is now discarded for several reasons; the Mezmaiskaya, Russia, Neanderthal is now dated to at least 36 kyr bp. The single AMS date on Cervus bone for Caldeirão (Portugal) will require revision and is likely, given the result for Hyaena Den of similar age, to be older than 30 kyr bp. Finally, the single 14C date, from Patella shells, from Figueira Brava, Portugal, is not statistically younger than 30 kyr bp (Finlayson et al. 2006, references omitted).

    So are the current radiocarbon dates for Gorham's Cave any better? Or, to put it another way, why exactly should we believe any new claims about recent dates, given the long list of dates that we are now supposed to forget about?

    Now, I'm not an archaeologist, nor am I a geochronologist. So maybe I'm missing something. But look at this figure from the paper (Figure 1c):

    Section from Gorham's Cave, showing points of radiocarbon sampling, Figure 1c from Finlayson et al. (2006).

    Notice sampling points 16, 17, and 20. Those are the key samples for the paper's conclusion:

    Thus, three samples (16, 17 and 20; Fig. 1) came from in situ Mousterian superimposed hearths. These three dates provide a stratigraphic sequence from 24,010 +- 320 to 30,560 +- 720 yr bp. Taken together, all the dates show that Neanderthals occupied the site until 28 kyr bp and possibly as recently as 24 kyr bp. The evidence in support of the 24 kyr bp date is more limited than for 28 kyr bp, which is taken as the latest well-supported occupation date (Finlayson et al. 2006).

    OK, so we have three samples from the same place in the cave, over a short vertical distance, that appear to represent successive occupations over a few-thousand-year interval. The authors interpret conservatively that maybe the 24,000-year date is too young to be Neandertal -- although they don't describe just what makes the evidence "more limited," considering each date is supported by a single radiocarbon sample.

    But look at sample number 11 in the figure. It appears to have been taken from directly above the putative hearths. So why does it have a date of 27,020 +/- 480 years?

    I think we begin to detect why there is "more limited" evidence for the 24,000-year date. It is directly controverted by the sequence.

    Moreover, we have to doubt the 26,000-year date, considering the evident contamination and/or turbation of the sample directly above it.

    Am I saying the Neandertals weren't in this cave after 30,000 years ago? Well, if you look at the samples in the figure, and their locations, almost all the samples taken from the brown zone (layer IV) have dates between 28,000 and 32,000 years BP. But there are several with dates between 26,000 and 23,000 years, and these are mixed in amongst or below earlier dates in the 28,000-30,000 year BP range.

    Please check out the dates yourself: Sample 23 (23,360 BP) is directly below sample 22 (29,720 BP). Sample 9 (26,070 BP) is directly adjacent to sample 10 (28,360 BP). Sample 15 (23,780 BP) appears to be stratigraphically below sample 14 (30,310 BP), although these are more spatially distant. Sample 28 (28,170 BP) is immediately below sample 27 (31,850 BP). Sample 29 (29,210 BP) is directly below sample 25 (31,780 BP). In all cases these discrepancies are outside the reported confidence limits.

    There seems to be clear evidence of widespread movement of material or contamination in this sequence.

    So, does the sheer weight of dates between 32,000 BP and 28,000 BP lead to the conclusion that the cave was occupied by Neandertals during that time range? Maybe so, but I think the paper raises a lot more questions than it answers. I have to think that we'll be hearing about how this date is equivocal or problematic, instead of it being the "latest Neandertal."

    References:

    Brill D. 2006. Neanderthal's last stand. Nature News 13 Sept. 2006. DOI link

    Finlayson C, and 25 others. 2006. Late survival of Neanderthals at the southernmost extreme of Europe. Nature, advanced online publication doi : 10.1038/nature05195

    Pendergast DM. 2000. The problems raised by small charcoal samples for radiocarbon analysis. J Field Archaeol 27:237-239.

    Tags: 
    Mousterian
    Europe
    Gibraltar
    Neandertals
    Upper Paleolithic
    Spain
    dating
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