Mousterian

We have known for many years that Lower Paleolithic people were using shellfish, fish, and littoral resources at sites across the Old World, from Trinil [1], Koobi Fora [2], Gesher Benot Ya'aqov [3], and elsewhere. I've discussed the evidence several times (maybe most usefully in "The shells of Trinil"). As I wrote last year ("Fishy story at Koobi Fora"):

Aquatic animals aren't important because of their sheer numbers, but because they tell us about the flexibility of foraging behavior. Living hunter-gatherers eat turtles and reptiles when they can, and because they are usually small food packages, they often eat them where they find them instead of returning to a base camp first. Hunter-gatherers are flexible in what they eat and where they eat it. FwJj20 is showing at least a substantial taxonomic flexibility in the meat-eating of early Oldowan hunters.

So why do we keep seeing stories that make shellfish consumption look like news when it's done by Neandertals, MSA Africans, or anybody else?

I'm writing about this today because of a new paper in PLoS ONE by Miguel Cortés-Sánchez and colleagues, reporting on the shellfish remains in Bajondillo Cave, Spain [4].

Shellfish collecting has been well characterized in some Mousterian contexts. Mary Stiner treated it systematically in her 1993 monograph, Honor Among Thieves, which is part of the graduate education of most young Paleolithic archaeologists. Stiner spent a lot of text quantifying shellfish use and gave a good discussion of the biases that make archaeologists find less evidence of shellfish consumption than there probably was.

Most important, when you can walk along a shoreline and nosh shells, you're not very likely to haul many of them back to a cave several kilometers from the shore. In the Holocene, we find lots of archaeological localities where people were systematically collecting many shells and cooking them for large groups. For this purpose, the people carried baskets or sacks of shellfish for a good distance, and after they were consumed, the shells sometimes built up into large trash piles, or middens. We don't see shell middens in Mousterian or MSA contexts, but then we see very little of that kind of behavior with any kind of resources in MSA or Mousterian times. Here's what I wrote in 2008 ("Neandertal diet was not dolphin safe"):

[I]t was hard to understand the excitement that accompanied last year's paper by Curtis Marean and colleagues (2007), who found evidence for shellfish exploitation at Pinnacle Point, South Africa. The press reported the result as if there were a shell midden, with abundant evidence for consumption. But actually the number of shells is fairly small -- all the shells from all the layers reported weigh less than a kilogram. That looks similar to the pattern of exploitation that Stiner had reported for the Neandertals at Moscarini, and more or less like the pattern at Vanguard and Gorham's Caves.

The African MSA-era site with the most direct evidence of shellfish exploitation is at Abdur, Eritrea, where the stone tools are found in an ancient shore terrace, presumably at the very place where shellfish exploitation was happening [5]. That paper hinted at even earlier sites with similar evidence from Acheulean contexts along the Red Sea rift, where subsidence of the rift floor has left some ancient coral reefs exposed, Acheulean tools embedded within them. I should also point out indirect evidence on the basis of species abundance for human exploitation of giant clams in the Red Sea ("The ancient struggle for existence between humans and giant clams").

In other words, archaeologists have found quite a lot of evidence of coastal resource use by early people, despite the steep biases against it. In the case of aquatic animal exploitation, they've got it as early as the Oldowan, 1.95 million years ago [2].

Cortés-Sánchez and colleagues [4] add detail to this record but don't really broaden the picture. Mousterian shellfish acquisition around 150,000 years ago, well before the last interglacial, is earlier than many well-known instances of MSA shellfish utilization. But we know that much earlier humans were using these coastal resources, so it's hardly news. As at other sites, the mollusc remains are not very dense: a minimum of 16 shells in one layer, 66 shells in another, 80 in a third. If I were going to make a story out of it, I would direct more attention to the pearl, first I've ever heard of in a Neandertal site.

More important is the paper's demonstration that humans actually processed the shells. Cortés-Sánchez and colleagues contrast the condition of continental and marine molluscs in the same levels, to show the systematic breakage and burning of the marine species:

[A]lmost all of the marine mollusks exhibit intensive mechanical fracturing, with sharp edges on their shells suggestive of an absence of post-depositional transport, and very few appear complete (i.e., barely 7% at Bj19). Such fracturing, coupled with the absence of shells eroded by water, indicates that the marine mollusks from Bajondillo Cave, and in particular those from Bj19 do not represent “background fauna” from the nearby beach, a phenomenon that has recurrently caused problems in the association of early Middle Paleolithic shellfish deposits from the Mediterranean with paleo-human activities. In addition, a substantial percentage of the mussels exhibit burning marks (Figure 4: 1–6). These are recorded on 48% of the adult specimens from Bj19, the young mussels never exhibiting such traces. Thermo-alterations suggest consumption rather than passive burning, given that in most cases only the outer portions of the shells appear carbonized and/or flaked. An indirect line of evidence supporting this same hypothesis is provided by five of the epibiont barnacle remains that fire not only detached from the mussel shells but that in that process were thoroughly carbonized, as is the case of the four specimens from Bj18 (Figure 4: 8,11) or else calcined, as happens with the specimen from Bj19 (Figure 4: 12).

I appreciate the paper's list of 24 previously-published Neandertal sites that present mollusc remains. It would be useful to compile a broader list including MSA sites. Personally, I hope to never read again a headline about how surprising or significant was shellfish use by early humans.

References

The science press has its own synchronized cycle, like brain waves, and being in Rome seems to make me into a misfiring neuron. Here it is tomorrow, and there's this story about Neandertals all being dead before modern humans showed up, which for Americans is now yesterday's news. Unless you take the paper NY Times, of course, in which case you probably haven't read it yet.

The occasion for the article is a paper reporting new radiocarbon dates for one of the specimens from Mezmaiskaya, a site in the Russian Caucasus.

The site and the date of the Mez 2 burial

Excavations by Golanova and colleagues have recovered two burials of young children from this site. One of them (Mez 1) has been the subject of much research. Based on some skeletal features and a partial sequence of its genome, the skeleton is a Neandertal child. A sample of one of its ribs was taken for radiocarbon dating, reported in 1999, and yielded a direct AMS date of 29,000 BP. This was out of sync with the other dates from the surrounding level of the site.

Ten years ago, Milford Wolpoff and I suggested that the skeletal features by themselves weren't very convincing, and a recent date (apparently out-of-sync with the surrounding archaeological layer) might signal an intrusive Upper Paleolithic burial [1], despite its Neandertal mtDNA sequence. Now we can look at a large part of the genome of this individual, which is very much like the Vindija Neandertals. In 2005, Skinner and colleagues reported ESR dates from Mezmaiskaya, concluding that layer 3 (including the Mez 1 burial) dates to between 60,000 and 70,000 years ago. By that time, those authors were discussing the inconsistency of the recent 29,000 date for the rib, compared to much older dates (>35,000 BP) for an overlying Mousterian layer. They expected the underlying layer 3 to be much older, and found that to be true of the ESR date estimates.

The second child burial, Mez 2, comes from layer 2 of the site, which is also Mousterian but younger than the first burial. A date around 40,000 years for the Mez 2 infant is basically what was expected six years ago by Skinner and colleagues:

Infant 2 was found in a pit introduced from Layer 2 into Layers 2A and 2B(1). Its’ age therefore is probably about 40 ka. Since the precise surface from which the pit was dug is unknown, this should be considered a maximum age.

That left open the possibility that the burial might be younger.

In the new paper [2], Ron Pinhasi and colleagues report that a sample taken from the infant itself dates to 39,700 +/- 1100 radiocarbon years BP, which calibrates to between 42,960 and 44,600 calendar years BP. The new date confirms that the burial happened relatively soon after the deposition of the surrounding dated bones.

The authors additionally report many other date estimates for faunal materials from the site. These form a pattern in which most are consistent with a relatively narrow range of date estimates, but a few are outliers. One of the important conclusions from the outliers is that contaminated carbon is hard to get out of a sample, even with the advanced ultrafiltration performed by the Oxford lab. The conclusion is narrowly interesting and solid, and it's very important to iron out such inconsistencies -- compare, for example, my 2008 post on the Gorham's Cave chronology.

So what is the big deal?

What does the paper say about the dates of other sites?

Here's where things get interesting. The paper includes this passage in its discussion:

The critical reanalysis of directly dated Neanderthal and AMH fossils from across Eurasia, taking into consideration pretreatment histories and redating results (5), supports our findings in the Caucasus and highlights the lack of reliably dated Neanderthal fossils younger than ∼40 ka cal BP (Fig. 3). Contrary to traditional arguments for up to 10,000 y of coexistence, these data suggest that Neanderthal extinction across Western Eurasia, including the Caucasus, was probably a rapid process, and that coexistence with AMHs, when it occurred, may have been of limited duration.

and this in its abstract:

Our results confirm the lack of reliably dated Neanderthal fossils younger than ∼40 ka cal BP in any other region of Western Eurasia, including the Caucasus.

That last part is a pretty strong statement. No reliably dated Neandertal fossils anywhere after 40,000 years ago?

I thought that was so surprising that I corresponded with the study authors today. One distinct advantage of being in Rome is that I'm synchronized with Europeans, so Tom Higham was able to write back with some of his thoughts. The authors' doubt in the later dates for Neandertal specimens is genuine; their experience is that the newer treatments to remove recent contaminating carbon from samples is eliminating Neandertal dates under around 40,000 years.

A systematic revision of the radiocarbon chronology of late Middle and early Upper Paleolithic Europeans has been underway for several years. This has been an important story, and I've written about it several times (my "dating" category hits most of the posts). I think I once told a journalist that this was the most underreported story in paleoanthropology.

In 2006, Higham and colleagues reported that dates obtained for the Vindija G1 Neandertals, at 29,000 BP, were too young by some 4000 years [3]. That result is listed in the current paper as "doubtful" becuase it did not employ the latest purification strategies. That helps to show that the current paper is "equal opportunity" -- past results from the Oxford Accelerator unit are not immune to doubt. But it is hardly confidence-raising. If we cannot trust radiocarbon determinations made in the last five years, why should anyone submit further samples for testing?

Personally, this was my reaction to the paper: don't grind up any more human bone until the radiocarbon community is unified about sample processing techniques. Let them work it out on the fauna.

The paper lists 15 direct dates on Neandertal specimens younger than 40,000 calendar years BP (some of them multiple samples from single skeletal remains). It lists all 15 of these as doubtful because they do not employ the latest techniques. That is a point emphasized by Higham also (and reflected in several past papers): these date determinatinos are not trustworthy given what we know about sample contamination by recent carbon-14. The Oxford group has put out several papers on this problem. One of the most useful is by Blockley and colleagues [4] because it introduces the device of using the Cantabrian Ignimbrite ash horizon as a marker to compare dates -- dates below the horizon should be consistent, whereas a large sample of actual date estimates include many that are far too young.

At any rate, this is where the story in the linked news article (and others) comes from. University College Cork issued a press release in conjuction with the paper's early edition release in PNAS.

Direct dating of a fossil of a Neanderthal infant suggests that Neanderthals probably died out earlier than previously thought. Researchers have dated a Neanderthal fossil discovered in a significant cave site in Russia in the northern Caucasus, and found it to be 10,000 years older than previous research had suggested. This new evidence throws into doubt the theory that Neanderthals and modern humans interacted for thousands of years. Instead, the researchers believe any co-existence between Neanderthals and modern humans is likely to have been much more restricted, perhaps a few hundred years. It could even mean that in some areas Neanderthals had become extinct before anatomically modern humans moved out of Africa.

This is the lead of the press release. I think that the claim makes up only a minor part of the paper (which is really a results paper about Mezmaiskaya). It is clearly interesting and provocative, but I think the paper's results by themselves do not justify the claim. In the case of Mez 2, a skeleton that the excavators expected to be 40,000 years old, actually turns out to be 40,000 years old. No surprise. There were no incorrect radiocarbon assessments of this specimen, and the apparently wrong assessment of the Mez 1 infant (at 29,000 years old instead of beyond radiocarbon range) has not been corrected here.

Were Neandertals really extinct by 39,000 years ago?

Now, in one sense, the survival of Neandertals after 40,000 years ago is not terribly important. Africans mixed with Neandertals, and as far as we can tell (an issue my lab is addressing now) the mixture is not preferentially within Europe. That argues for a West Asian interaction of the population, and it remains to understand why the ancestors of Europeans did not interact more than other populations. Probably a good hypotheses is that today's Europeans derive most of their ancestry from outside Europe during the last 10,000 years. If the Neandertals did not persist within Europe long during the Upper Paleolithic, that provides another alternative.

But to say that we doubt a particular kind of information about dates is not the same as saying that Neandertals did not exist after 39,000 years ago.

Direct dates on Neandertal bones are far from the only evidence of their persistence in Europe. Dozens of sites are dated by radiocarbon on fauna or charcoal. These dates themselves may be subject to the same critique as applies to the human bone. But there are not 15 of them, there are many, many more.

For example, Gravina and colleagues [5] list 24 AMS dates for Châtelperronian contexts that are 36,000 BP or less. Calibration of dates for this era adds more than 3000 years or more to the calendar years represented by a radiocarbon date, so these are dates likely less than 40,000 years. They may be contaminated by recent carbon (and indeed a few are outliers below 32,000 BP), but if so some of them are remarkably consistent.

Martínez-Moreno and colleagues [6] give a recent review of the Middle-Upper Paleolithic transition in Iberia. They list several sites with late Mousterian industries later than 34,000 radiocarbon years BP, even without counting the contentious examples (like Gorham's Cave) that arguably are later than 30,000 BP.

I would not be happy assuming that every Mousterian site is a Neandertal site, not even in this limited geographic context. There is too much technical overlap, and sometimes small samples of artifacts, to be definitive about such an association. Technology is not biology. Neither would I be willing to assume that late Neandertals are entirely Neandertal -- we see no genetic evidence of African mixture into this population in the Vindija or El Sidron genomes, but these are older than 45,000 years. Who knows what a 35,000-year-old Neandertal in France or Spain (or Croatia) would look like genetically? But only Neandertal remains have thus far been associated with Mousterian and Châtelperronian in France and Iberia. Several sites have stratified Middle to Upper Paleolithic transitions with dates after 40,000 calibrated years BP.

So from the Neandertal point of view, I think this is largely a non-story. There remains substantial question about the pattern of appearance of the post-Neandertal population, as I've extensively discussed here. When we consider the Caucasus, we are still working to understand the timing and mode of the later Neandertals and early Upper Paleolithic people. But there's really no serious challenge to the idea that Neandertals existed in Western Europe after 40,000 years ago.

Or if there is, it'll be out of sync with what most of us think we know.

References

GRRRRRR! Why do I have to keep reading about how spearchucky modern humans went around killing Neandertals?

It's all over the science news this week -- Shanidar 3, a 50,000-year-old Neandertal from Iraq, has a partially-healed deep cut to one of its ribs. The kind of cut that gets there when you're stabbed with a knife or spear, or shot with an arrow.

That's pretty interesting in itself, although not news -- the wound has been known and listed as an example of ancient interpersonal violence since the 1960's. It may be the oldest clear example of a wound to a living person from a stone implement, because all earlier cutmarked human remains (there are many) may be post-mortem. Still, not news.

The "news" part is that Churchill and colleagues (2009) have shown that the wound is most consistent with a small projectile, as opposed to a large thrusting spear. In their discussion, they suggest that modern humans may be the culprits:

The nature of the lesion to the left 9th rib of the Shanidar 3 Neandertal is most consistent with injury from a low kinetic energy, low momentum weapon. While this does not rule out accidental injury or attack by a conspecific wielding a hand-held weapon, the nature of the traumatic damage, combined with the wound track suggested by the placement and orientation of the rib lesion, is consistent with injury by a long-range projectile weapon traveling along a ballistic trajectory. Given the possible sympatry of this Neandertal with early modern humans, and given possible assymetries in weapon technology between the two species, the case of Shanidar 3 is a good candidate for an instance of Neandertal-modern human interspecific violence (14, emphasis in original).

So what do I think? I guess anything is possible. But any good murder case hinges on motive and opportunity. Churchill and colleagues don't really give us a way to place modern humans at the scene at the crime.

The authors point to the only radiocarbon dates available for Shanidar 3, which at 46,000 and 50,000 radiocarbon years are in a range that we probably should not trust for old, non-AMS dates (as they point out). There's no indication of a non-Mousterian industry in the immediate region before 35,000 radiocarbon years, although an earlier presence of non-Neandertals is possible.

As it stands, what are the odds that the Neandertal Shanidar 3 individual (setting aside the question of whether it or other West Asian specimens really are the same as European Neandertals) would ever have encountered a "modern" human (setting aside the question of whether the two populations were distinct)?

Well, we don't really know. Probably pretty low. Maybe impossible. But that probability is very important to this "forensic" question.

Do we know that Shanidar 3 wasn't hit by a Neandertal weapon? The study shows very well that seven blows from a Mousterian point-hafted spear are not enough to guarantee a wound like the one on the ribs of Shanidar 3. That wound has a clear cut to one rib but little involvement of the adjacent rib. The seven experimental blows from a "high-energy" weapon resulted in five wounds with significant slices in two adjacent ribs, and two that affected no ribs at all. In contrast, the "low-energy" trials generated a high fraction of wounds that involved slices to only one rib. Meanwhile, two of those "low-energy" trials were from a Neandertal-associated tool, stabs with a Levallois point.

But what does this tell us, really? If we just treat the probability of a Shanidar 3-type injury as a binomial with 7 trials in this study, we can't reject the hypothesis that it occurs at a true likelihood of 35 percent. I think the authors have done a cool study, and did a great job evaluating the wounds. The problem is that 7 trials just isn't enough to yield a high confidence. We don't really know that a weapon known to be associated with Neandertals couldn't have made the wound.

So it comes down to opportunity. Can we place modern humans at the scene of the crime?

We may not be able to estimate this probability, but we can use Bayes' theorem to evaluate what the likelihood would have to be to satisfy our jury. Let's say our jury is stacked with Neandertals, and is willing to convict a modern human if there is just a five percent chance he committed the crime.

1. We don't know the probability that Shanidar 3 encountered modern humans. We'll assume that Shanidar 3 would have been attacked with equal probability by whomever he encountered. Hence, the encounter rate with modern humans, the chief unknown, directly determines the chance of being wounded by a modern human.

2. We do know something about the probability that a random injury from a high-energy Neandertal-made weapon would have the characteristics of the Shanidar 3 wound -- it's something less than 35 percent.

3. We'll assume the probability of Levallois point stabs is zero, thereby stacking the deck in favor of a modern human killer.

4. We know that a random wound from a modern human projectile weapon would generate a wound having those characteristics with something like a 50 percent probability.

Plugging into Bayes' theorem, that means that an encounter rate of 1 modern human for every 28 Neandertals would yield a five percent chance that a modern human was the culprit. Did Shanidar 3 encounter one modern human for every 28 of his own? If not, we have to conclude its very unlikely -- less than five percent -- that his wounds were caused by a modern human.

At the moment, the best evidence from the site suggests that Shanidar 3 lived fifteen thousand years before any archaeological transition to the "low-energy" impactors. Which tilts the scales in favor of the alternative -- a slightly lower probability impact from a much higher probability weapon.

References:

Churchill SE, Franciscus RG, McKean-Peraza HA, Daniel JA, Warren BR. 2009. Shanidar 3 Neandertal rib puncture wound and paleolithic weaponry. J Hum Evol (early online) doi:10.1016/j.jhevol.2009.05.010