Monthly Archives: June 2013

Revisiting the demographics of Northern and Central Europe in the Neolithic and Chalcolithic periods

Stimulated by the discussion at another entry, yesterday I made a little graph, almost a mnemonic, on the demographics of Northern European Neolithic and Chalcolithic, based on academic data which I discussed back in 2009.
This is the result:

The very simplified graph is nothing but a version of another one, used in 2009 (and reproduced below), which in turn is an annotated and composite version extracted from two different studies (references also below).
For convenience I have marked the millennia marks at the bottom (meaning 5000, 4000, 3000 and 2000 BCE, from left to right) while the unmarked vertical scale ranks from 0 to 100 (marked by the lowest and highest dots, not the frame, which is actually outside of the graph itself). The dots mark population level at any time as proportion of the maximum (100) in discrete intervals rounded up/down to 10 ppts and taken at intervals of 250 years. Notice that I ignored monuments in the case of Britain, only considering the habitation and other productive sites.
Not sure if it will result useful to you but it did help me to visualize the demographics of Northern Europe in these four millennia of surely dramatic population changes. If you don’t like this version the more detailed original double graph is below, scroll down.
Something quite obvious is that while Danubian Neolithic first caused an important population expansion, it later declined to quite low population levels, maybe because of climatic cooling and the exhaustion of the lands because of poorly developed agricultural techniques. 
This late Danubian collapse lasted for about a millennium, when (1) Funnelbeaker (TRBK) in Denmark, (2) Megalithism in Britain and Denmark especially (later also in parts of Germany) and (3) Kurgan cultures in Poland (later also in Germany and Denmark) seem to have brought with them very notable demographic expansions.
But decline seems to set on again all around at the end of the Chalcolithic period, much more notably in the continent (in Poland the rate of archaeological findings decays to zero!) than in Britain and especially Denmark. 
And now indeed the original “verbose” graph:

And the sources:

Was the grove snail Epipaleolithic livestock in Western Europe?

Cepaea nemoralis
(CC by Papa Lima Whiskey 2)
The problem of disjunct distribution of Western European species or, in this case, subclades of a single species is nothing new and has been startling biologists for almost two centuries already, with particular interest of Irish-Iberian, Breton-Iberian or just general Irish-continental disjunct relationships of various species (the so called Lusitanian distribution). Among them is the iconic strawberry tree (madroño in Spanish, found in Ireland but not Great Britain) but also a number of small land animals: the Kerry slug (found in NW Iberia and SW Ireland only), the Quimper snail (found in NW Iberia and Western Brittany) or the Pyrenean glass snail (found in the Pyrenees and Ireland).
There are also cases of subclades within an otherwise widespread species which show a similar pattern. In 2003, Masheretti et al. demonstrated that the Irish variant of the pygmy shrew had its greatest affinity with populations of Andorra, in the Eastern Pyrenees, from which they are descended.
This study illustrates a similar case but affecting the snail species Cepaea nemoralis (grove snail or brown lipped snail), whose Irish lineages are mostly derived from Iberian ones and in most cases from the Eastern Pyrenean haplogroup C.
Adele J. Grindon & Angus Davison, Irish Cepaea nemoralis Land Snails Have a Cryptic Franco-Iberian Origin That Is Most Easily Explained by the Movements of Mesolithic Humans. PLoS Genetics 2013. Open access LINK [doi:10.1371/journal.pone.0065792]


The origins of flora and fauna that are only found in Ireland and Iberia, but which are absent from intervening countries, is one of the enduring questions of biogeography. As Southern French, Iberian and Irish populations of the land snail Cepaea nemoralis sometimes have a similar shell character, we used mitochondrial phylogenies to begin to understand if there is a shared “Lusitanian” history. Although much of Europe contains snails with A and D lineages, by far the majority of Irish individuals have a lineage, C, that in mainland Europe was only found in a restricted region of the Eastern Pyrenees. A past extinction of lineage C in the rest of Europe cannot be ruled out, but as there is a more than 8000 year continuous record of Cepaea fossils in Ireland, the species has long been a food source in the Pyrenees, and the Garonne river that flanks the Pyrenees is an ancient human route to the Atlantic, then we suggest that the unusual distribution of the C lineage is most easily explained by the movements of Mesolithic humans. If other Irish species have a similarly cryptic Lusitanian element, then this raises the possibility of a more widespread and significant pattern.

The evidence gathered by this study is most readily visible in fig. 2:

While it is not the focus of this study, we see here two other cases of probable disjunct distribution:
  • Hg D is found in Iberia, Ireland, small pockets in Britain and SW France but also in North and Central Europe.
  • Hg F shows also disjunct presence in Cornwall, far away from the main cluster around the Bay of Biscay.
The authors of this and previous studies have suggested that this distribution may have to do with intentional transport (as livestock) in the process of the colonization of the Atlantic Islands in the Epipaleolithic. In support of this claim, there is enough fossil evidence of the snail in the island:

Fossil material indicates that this species has been continuously present in Ireland for at least 8000 years (Newlands Cross, Co. Dublin: 7600+/−500 BP Cartronmacmanus, Co. Mayo: 8207+/−165) [7], [8].

In other cases, such as the inedible Kerry slug, we may suspect unintentional transport and therefore we would be justified to imagine a later time frame for their arrival to Ireland, possibly in the Chalcolithic-Megalithic period, but the evidence for C. nemoralis is highly suggestive of intentional transport in the Epipaleolithic. We can therefore say that the humble grove snail was one of the first domestic animals of Europe, possibly second after the dog.

The less homogeneous European "populations" are Italians and French

This comes from a recent IBD study on Europe:
Peter Ralph & Graham Coop, The Geography of Recent Genetic Ancestry across Europe. PLoS Biology, 2013. Open accessLINK [doi:10.1371/journal.pbio.1001555] 


The recent genealogical history of human populations is a complex mosaic formed by individual migration, large-scale population movements, and other demographic events. Population genomics datasets can provide a window into this recent history, as rare traces of recent shared genetic ancestry are detectable due to long segments of shared genomic material. We make use of genomic data for 2,257 Europeans (in the Population Reference Sample [POPRES] dataset) to conduct one of the first surveys of recent genealogical ancestry over the past 3,000 years at a continental scale. We detected 1.9 million shared long genomic segments, and used the lengths of these to infer the distribution of shared ancestors across time and geography. We find that a pair of modern Europeans living in neighboring populations share around 2–12 genetic common ancestors from the last 1,500 years, and upwards of 100 genetic ancestors from the previous 1,000 years. These numbers drop off exponentially with geographic distance, but since these genetic ancestors are a tiny fraction of common genealogical ancestors, individuals from opposite ends of Europe are still expected to share millions of common genealogical ancestors over the last 1,000 years. There is also substantial regional variation in the number of shared genetic ancestors. For example, there are especially high numbers of common ancestors shared between many eastern populations that date roughly to the migration period (which includes the Slavic and Hunnic expansions into that region). Some of the lowest levels of common ancestry are seen in the Italian and Iberian peninsulas, which may indicate different effects of historical population expansions in these areas and/or more stably structured populations. Population genomic datasets have considerable power to uncover recent demographic history, and will allow a much fuller picture of the close genealogical kinship of individuals across the world.

Most interesting in my understanding is table 1 (right), which describes the IBD relation of the sampled populations within themselves and with other Europeans.
From this table it seems very apparent that Italians and French are not homogeneous at all and therefore, in my opinion, should not be treated as single populations in genetic studies but butchered at least a bit by regions (whose optimal dimensions are yet to be determined).
The degree of internal homogeneity of the samples (only n=5 or greater) can be simplified as follows:
  • Very low (<1): Italy, France.
  • Quite Low (1-1.4): Germany, UK, Belgium, England, Austria, French-Swiss, 
  • Somewhat low (1.5-1.9): Spain, German-Swiss, Greece, Portugal, Netherlands, Hungary.
  • Somewhat high (2-2.9): Czech R., Romania, Scotland, Ireland, Serbia, Croatia,
  • Quite high (3-3.9): Sweden, Poland
  • Very high (4-5): Bosnia, Russia*
  • Extremely high (>10): Albania
  • I ignored strangely labeled samples like “Switzerland” and “Yugoslavia”, which seem to mean actually “other” within these labels.  I retained the “United Kingdom” category for its large sample size, much larger than its obvious parts.
  • The level of relatedness of Russians may be exaggerated by the small sample: n=6, still above my cautionary threshold. 
  • I suspect that the extreme disparity of sample sizes may influence the results to some extent.
Eastern Europeans seem much more strongly related with others, especially other Eastern Europeans, than Western ones, while NW Europeans are more related with other groups (usually at regional level) than SW ones. In fact the Italian and Iberian peninsula show very low levels of “recent” relatedness with other populations, which is a bit perplexing, considering their non-negligible roles in Medieval and Modern European history. I guess that this may be partly caused by geographic barriers (mountains) and also by these areas having large populations since Antiquity or before. 

Figure 3. Geographic decay of recent relatedness.
In all figures, colors give categories based on the regional groupings of Table 1. (A–F) The area of the circle located on a particular population is proportional to the mean number of IBD blocks of length at least 1 cM shared between random individuals chosen from that population and the population named in the label (also marked with a star). Both regional variation of overall IBD rates and gradual geographic decay are apparent. (G–I) Mean number of IBD blocks of lengths 1–3 cM (oldest), 3–5 cM, and >5 cM (youngest), respectively, shared by a pair of individuals across all pairs of populations; the area of the point is proportional to sample size (number of distinct pairs), capped at a reasonable value; and lines show an exponential decay fit to each category (using a Poisson GLM weighted by sample size). Comparisons with no shared IBD are used in the fit but not shown in the figure (due to the log scale). “E–E,” “N–N,” and “W–W” denote any two populations both in the E, N, or W grouping, respectively; “TC-any” denotes any population paired with Turkey or Cyprus; “I-(I,E,N,W)” denotes Italy, Spain, or Portugal paired with any population except Turkey or Cyprus; and “between E,N,W” denotes the remaining pairs (when both populations are in E, N, or W, but the two are in different groups). The exponential fit for the N–N points is not shown due to the very small sample size. See Figure S8 for an SVG version of these plots where it is possible to identify individual points.
We can also see in the above figure (bottom) how most of the relatedness, especially along longer distances belongs to the oldest dates (1-3 cM).
The authors suggest that low heterogeneity within some of these groupings is influenced by regional variation, what makes good sense to me. This they illustrate with the examples of Italy and Great Britain:

Figure 2. Substructure in (A) Italian and (B) U.K. samples.
The leftmost plots of (A) show histograms of the numbers of IBD blocks that each Italian sample shares with any French-speaking Swiss (top) and anyone from the United Kingdom (bottom), overlaid with the expected distribution (Poisson) if there was no dependence between blocks. Next is shown a scatterplot of numbers of blocks shared with French-speaking Swiss and U.K. samples, for all samples from France, Italy, Greece, Turkey, and Cyprus. We see that the numbers of recent ancestors each Italian shares with the French-speaking Swiss and with the United Kingdom are both bimodal, and that these two are positively correlated, ranging continuously between values typical for Turkey/Cyprus and for France. Figure (B) is similar, showing that the substructure within the United Kingdom is part of a continuous trend ranging from Germany to Ireland. The outliers visible in the scatterplot of Figure 2B are easily explained as individuals with immigrant recent ancestors—the three outlying U.K. individuals in the lower left share many more blocks with Italians than all other U.K. samples, and the individual labeled “SK” is a clear outlier for the number of blocks shared with the Slovakian sample.
In the UK, there is a negative correlation between blocks shared with Ireland and those shared with Germany, what seems to imply a dual origin of Britons. 
Age estimates (double them?):
The authors also get to estimate ages, however it seems obvious from their own data that the results should be multiplied by 2.2 or something like that to make good sense:

Figure 4. Estimated average number of most recent genetic common ancestors per generation back through time.
Estimated average number of most recent genetic common ancestors per generation back through time shared by (A) pairs of individuals from “the Balkans” (former Yugoslavia, Bulgaria, Romania, Croatia, Bosnia, Montenegro, Macedonia, Serbia, and Slovenia, excluding Albanian speakers) and shared by one individual from the Balkans with one individual from (B) Albanian-speaking populations, (C) Italy, or (D) France. The black distribution is the maximum likelihood fit; shown in red is smoothest solution that still fits the data, as described in the Materials and Methods. (E) shows the observed IBD length distribution for pairs of individuals from the Balkans (red curve), along with the distribution predicted by the smooth (red) distribution in (A), as a stacked area plot partitioned by time period in which the common ancestor lived. The partitions with significant contribution are labeled on the left vertical axis (in generations ago), and the legend in (J) gives the same partitions, in years ago; the vertical scale is given on the right vertical axis. The second column of figures (F–J) is similar, except that comparisons are relative to samples from the United Kingdom.

I say that mainly because the shared ancestry between Balcans and both Italy and France is dated here to around 3000 or 3500 years ago, when it would fit much better to c. 7500 years ago (as much as 8000 BP for some parts of Italy), when the Neolithic expansion was ongoing. There is no particular reason why the Balcans would be related to France and Italy c. 3000 years ago specifically, unless one believes in undocumented massive Mycenaean migrations or something like that (and what about Albania then?)
However I am getting a headache with this issue because no correction, low or high seems good enough for all pairs, so, well, just take this part with your usual dose of healthy skepticism.
Some (annotated) excerpts:

In most cases, only pairs within the same population are likely to share genetic common ancestors within the last 500 years [i.e.: ~1100 years]. Exceptions are generally neighboring populations (e.g., United Kingdom and Ireland). During the period 500–1,500 ya [i.e. ~1100-3300 years ago: most of the Metal Ages], individuals typically share tens to hundreds of genetic common ancestors with others in the same or nearby populations, although some distant populations have very low rates. Longer ago than 1,500 ya [i.e. before ~3300 years ago: before the Late Bronze Age crisis], pairs of individuals from any part of Europe share hundreds of genetic ancestors in common, and some share significantly more.

On Italy:

There is relatively little common ancestry shared between the Italian peninsula and other locations, and what there is seems to derive mostly from longer ago than 2,500 ya [i.e. ~5500 y.a.: Megalithic era onwards]. An exception is that Italy and the neighboring Balkan populations share small but significant numbers of common ancestors in the last 1,500 years [i.e. after 3750 years: since the Mycenaean period]

On Iberia:

Patterns for the Iberian peninsula are similar, with both Spain and Portugal showing very few common ancestors with other populations over the last 2,500 years [i.e. 5500 years: Megalithic era onwards]. However, the rate of IBD sharing within the peninsula is much higher than within Italy… 

The low Iberian relationship with other populations seems to preclude this region as source for the conjectured re-expansion of mtDNA H and other Western lineages. I would suggest looking to (Western) France for an alternative source, as this state’s heterogeneous population shares more intense relations with other Western peoples around what could be c. 6200 BP, what is at the very beginning of Megalithic spread in Atlantic Europe, for which Armorica (Brittany and neighboring Western France) could well have been a major source (and definitely was in the case of Britain).
Of course, if you prefer to use the authors’ estimates, it would have no influence on the hypothesis because they simply can’t reach so far back in time, it seems. But I feel more comfortable overall reformulating the hypothesis towards Armorica.
For better reading of each pair of relationships through time, I include here fig. S16:

The maximum likelihood history (grey) and smoothest consistent history (red) for all pairs of population groupings of Figure S12 (including those of Figure 5). Each panel is analogous to a panel of Figure 4; time scale is given by vertical grey lines every 500 years. For these plots on a larger scale, see Figure S17.

As said before, I suggest to read each vertical grey line (counting from left) as meaning ~1100 years rather than just 500.

Update (Jun 23): on IBD-based molecular-clock-o-logy:

I have now and then found strange insistence on IBD-based chronological estimates being almost beyond reasonable doubt. I admittedly don’t know a great deal on the matter, so when Davidski (see comments) insisted again on that, I asked him for a reference, so I could learn something. He kindly suggested me to read Gusev et al. 2011, The Architecture of Long-Range Haplotypes Shared within and across Populations, which is indeed a good paper. However I could not find the clearly explained basis for the chronological estimates in general, probably buried deep in the bibliography. What I found instead was a clear example of these being short from historical reality by a lot.

This example corresponds to one of the best documented populations to have suffered a “recent” bottleneck event: Ashkenazi Jews (AJ). According to Gusev et al., these would have suffered a bottleneck (founder effect of some 400 nuclear families followed by expansion) around 20 generations ago (~600 years = 1400 CE) or, a few lines later more specifically: 23 generations ago (~1320 CE). So here we do have a clear case study.

When we look at historical reality however, it is just impossible that AJ would have their founder effect bottleneck so late. Historical records document them often already in the Frankish period and they were definitely a vibrant expanding community by the time of the founding of Prague and Krakov c. 900 CE. A historical reasonable estimate for the AJ founder effect should be instead c. 700 CE, when they begin to appear in historical records, or maybe even a bit earlier, because of the lack of documentation in the Dark Ages.

That is not at all a mere 20-23 generations ago but almost double (counting generation time = 30 years, if gen-time would be 27 years, for example, the difference between estimates and reality would be even greater). Assuming a very reasonable AJ founder effect at 700 CE, then:

  • For gen-time = 30 years → 43 generations till now → 43/23 = 1.9 times for realistic correction
  • For gen-time = 27 years → 48 generations → 48/23 = 2.1 times for realistic correction
  • For gen-time = 25 years → 52 generations → 52/23 = 2.3 times for realistc correction

While it has become nowadays standard issue to assimilate generation time to 30 years, this is not any absolute measure because the actually observed generation time (i.e. the age difference between parental and child generations on average) varies in real life depending on cultural factors (such as marriage age), gender (female generation time is almost invariably shorter than male), life expectancy (mothers dead at birth at young age, for example, don’t have any more children), etc. So it is in the fine detail a somewhat blurry issue, with some significant variability among cultures and surely also through time.

Another issue is if this “short term” estimate correction is stable along time or does in fact vary somewhat. I can’t say.

Whatever the case, the approximate x2 correction proposed above, seems to stand in general terms.


New Maya city discovered

Archaeologists have discovered the ruins of a long lost Maya city in the jungle SE of Campeche state (Yucatan Peninsula, Mexico), in the historical Maya region of the central lowlands. 

The newly discovered city, Chaktún, occupies some 22 Ha. and is believed to have been an important local power between 600 and 900 CE. It was hidden in the northern area of the Biosphere Reserve of Calakmul, near the Guatemalan border.

Source: Paleorama[es].


Korean petroglyphs at risk by reservoir

A group of very beautiful South Korean petroglyphs that seem to represent whale hunting and are dated some 6000 years ago are being damaged by a water reservoir that provides water for the city of Ulsan. 

The Bangudae petroglyphs, discovered in 1971, are submerged under water seasonally, raising great controversy in the East Asian country. It seems that even President Park is greatly concerned about them, something not too usual in a politician, while the Cultural Heritage Administration is demanding measures to protect the ancient rock art, namely to keep water levels low enough. 
However water utilities claim that it is impossible to meet such demands while providing water to the seventh largest South Korean city. The Ulsan city government is proposing to build a wall around the petroglyphs in order to protect them while keeping the water levels, this however would cause environmental damage to the area, disqualifying the site for UNESCO World Heritage protection schemes.
Source: cinabrio.over-blog[en/es] (incl. several pictures and press articles).

Mellars 2013: second round

As I mentioned before, I have already got copies of the controversial study by Paul Mellars et al., which argues for a very late colonization of Eurasia. It includes some aspects not dealt with in the first round, when I could only access the supplemental material. 
Paul Mellars et al., Genetic and archaeological perspectives on the initial modern human colonization of southern Asia. PNAS 2013. Pay per view (6-month embargo) → LINK [doi:10.1073/pnas.1306043110]
Maybe the most important is the very striking visual comparison between proto-LSA African microlithic industries and post-UP South Asian microlithic ones:

While it is maybe easy to dismiss the patterns drawn on ostrich shells in Africa and South Asia as not really looking the same at all and therefore likely coincidence, the visual comparison of the industries is much harder to reject. It does indeed pose a mysterious apparent link similar to others that are hard to explain like the similitude between Chatelperronian and Gravettian (not so long ago treated together as “Perigordian”) or the hammering insistence by some rather marginal academics on the similitudes between the SW European Solutrean culture and the (much more recent) North American Clovis industry. 
Sure: impressive and intriguing. But when it comes to chronology the Mellars hypothesis seems to fail terribly. While the African microliths are pre-LSA and therefore from before ~49,000 years ago in all cases, the South Asian ones only show up mostly since c. 34-38,000 years ago, more than ten millennia later. Mellars makes this figure 40-35 Ka and then just 40 Ka for the following graph, which in fact misrepresents Petraglia’s model and data in a key issue (see below):

It must be emphasized here that Petraglia’s data and model, at least for what I know it, implies an hiatus between c. 110 Ka and c. 80 Ka BP, hiatus for which there is no archaeological data of any kind in South Asia. Therefore neither side graph should suggest continuity to the past before ~80 Ka, allowing at most for a highly hypothetical dotted line (as in Petraglia 2010):

Also there is nothing in Petraglia’s work that could suggest discontinuity at the Toba ash layer, as suggested by Mellar’s version, rather the opposite: continuity is very apparent in Jwalapuram:

Jwalapuram industries (from Petraglia 2007)

Quite conveniently Mellars ignores Petraglia’s data again, which suggest continuity before and after microlithism in Jurreru Valley and then also finds a transition towards UP (“blade and bladelet”, as well as “backed artifacts”) technologies since c. 34 Ka BP. 
But regardless, I’m pretty sure that Prehistory-savvy readers have already noticed a major issue in all this chronology: we are talking of dates that are almost 20,000 years after the colonization of West Eurasian by H. sapiens with “Aurignacoid” technologies, which are dated to before 55 Ka BP in Palestine (OSL), to c. 49 Ka BP in Central Europe and to c. 47 Ka BP in Altai (C14 calibrated). 
And those who are also familiar with Eurasian population genetics are by now shaking their heads in disbelief and claiming to heaven and hell alike. Because West Eurasians derive, at a late relative date, from Tropical Asians and therefore, if our core ancestors were already separated before 55 Ka BP, there is just no room for the Tropical Asian (and Australasian) expansion that must have preceded the Sapiens colonization of the West Eurasian Neanderlands.
(Those unfamiliar with the basics of Eurasian population genetics, see here).
So there is no way that the Out of Africa migration could be dated to just c. 55 Ka BP, as Mellars does (after grabbing hard the burning nail of conjectural coastal sites now under the sea, which would have to account for some 15-20,000 years of Eurasian prehistory on their own).
In fact it is also impossible from the viewpoint of Australian chronology, which again needs to go after the settlement of Tropical Asia but surely before that of West Eurasia. 
So, regardless of the striking visual comparison between African and Indian industries, which is no doubt the “bunny in the hat” here, the Mellars hypothesis simply doesn’t stand. 
Was there another cultural (surely not demic) flow from Africa to South Asia c. 40-35 Ka BP? Maybe. Or maybe it is just one of the many hard-to-explain coincidences in stone industry design. But whatever it is, it just cannot be the Out-of-Africa migration, unless one is ready to accept that Aurignacian and related European rock art, as well as Australian rock art, for example, are the product of archaic homo species (something that I am sure that Mellars won’t admit to: it just goes against his “modern human behavior” prejudices). And, even then, it just doesn’t add up either.

PS- Petraglia himself finds Mellar’s alternative model untenable. From ABC Science (emphasis mine):

… Professor Michael Petraglia, an archaeologist from the University of Oxford disputes Richards’ and Mellars’ argument. 

Petraglia says there’s not enough evidence to rule out an earlier colonisation before the eruption of Mount Toba. 

“The research reported by Mellars and colleagues is riddled with problems,” he says. 

Petraglia says that the similarity between tools used in Africa
60,000 years ago and those from Asia dating to around 35,000 years ago
is not a consequence of direct migration.

“These toolkits are separated in time by more than 20,000 years and distances exceeding several thousand miles.” 

He questions the evidence supporting a migration along the coast. He
says that surveys of ancient shorelines have not revealed any evidence
for human settlements anywhere along the Indian Ocean shore between
55,000 and 50,000 years ago.

He also says genetic dating should be treated cautiously. 

“Most geneticists will admit that genetic dating of the out-of-Africa
event is tenuous, at best. Published genetic ages for out-of-Africa
range anywhere between 45,000 to 130,000 years ago.

says his team is currently conducting archaeological fieldwork in
Arabia, India and Sri Lanka they expect will show that the story of
human dispersal from Africa is complex.

“What we can agree on is that little research in these key geographic
regions has been conducted and much more evidence needs to be collected
to support or refute the different theories,” says Petraglia.


Mellars challenges the ‘early out of Africa’ model

I do not have yet access to this potentially key paper, so first of all I want to make an appeal here to share a copy with me (→ email address). Thanks in advance. Update: got it (thanks to all who shared, you people are just great!) I will review it again as soon as possible.

Update (Jun 18): complementary review of the full paper now available here.

Paul Mellars et al., Genetic and archaeological perspectives on the initial modern human colonization of southern Asia. PNAS 2013. Pay per view (6-month embargo) → LINK [doi:10.1073/pnas.1306043110]


It has been argued recently that the initial dispersal of anatomically modern humans from Africa to southern Asia occurred before the volcanic “supereruption” of the Mount Toba volcano (Sumatra) at ∼74,000 y before present (B.P.)—possibly as early as 120,000 y B.P. We show here that this “pre-Toba” dispersal model is in serious conflict with both the most recent genetic evidence from both Africa and Asia and the archaeological evidence from South Asian sites. We present an alternative model based on a combination of genetic analyses and recent archaeological evidence from South Asia and Africa. These data support a coastally oriented dispersal of modern humans from eastern Africa to southern Asia ∼60–50 thousand years ago (ka). This was associated with distinctively African microlithic and “backed-segment” technologies analogous to the African “Howiesons Poort” and related technologies, together with a range of distinctively “modern” cultural and symbolic features (highly shaped bone tools, personal ornaments, abstract artistic motifs, microblade technology, etc.), similar to those that accompanied the replacement of “archaic” Neanderthal by anatomically modern human populations in other regions of western Eurasia at a broadly similar date.

A review has been published at Live Science.

South Asian artifacts from ~30-50 Ka BP.

By “genetic evidence” they obviously mean “molecular clock” nonsense, so it is not evidence at all but mere speculation. However I am indeed very interested in knowing in detail what they mean by “archaeological evidence”, because they seem to get into direct confrontation with much accumulated evidence, first and foremost all of Petraglia’s research in both India and Arabia but also with the quite strong evidence for pre-60 Ka human presence in Australia and growing evidence for pre-60 Ka modern humans in SE Asia (in some cases even as old as 100 Ka). 
It must be said that Paul Mellars has been criticized before a lot for several reasons but very especially for his adherence to the quite speculative “modern human behavior” conjecture and, relatedly, bigotric attitudes against Neanderthal intellectual capabilities, based on nothing too solid. Therefore I’m generally skeptic about what Mellars has to say on this matter because this kind of conclusion is what one would expect from him. 
However Mellars is certainly a distinguished academic and, even if prejudiced and stuck to his own old-school and somewhat Eurocentric interpretations, he knows his trade as archaeologist and prehistorian. So he may be onto something, even if it is not exactly what he wants us to believe. 
For example, it is not impossible that this research may have, unbeknown to the authors, found evidence of a secondary OoA wave (maybe related to the spread of Y-DNA D and mtDNA N?) or even a distinctive evolution in Southern Asian technology prior to the expansion of Western Eurasia. 
It is interesting that they suggest that the 80-60/50 Ka toolkits of India would have been made by Neanderthals, when they are not describing them at all as Mousterian, the almost exclusively Neanderthal techno-culture, or Mousterian-related.
I have some difficulties judging before reading the whole study. However the supplemental material (quite extensive) is freely accessible and for what I can see there:
  1. They dedicate much text to attempt to justify a particular version of mainstream “molecular clock” hypothesis, which are clearly broke in my understanding. The kind of arguments “rebated” are more or less what I have been putting forward since many years ago. Ironically their “molecular clock” estimates make N and R much older than M, what I absolutely oppose (just count mutations downstream of the L3 node).
  2. No real attention is given instead to the geographical structure/distribution of major mtDNA haplogroups, only mentioned in relation to “molecular clock” speculations.
  3. The criticism of the African affinity of the Jwalapuram (Jurreru Valley) cores (Petraglia 2007) focuses on dismissal of any possibility of comparison, rather than on alternative comparisons. 
  4. Another “criticism” is that there is no apparent connection between Jwalapuram and the Nubian Complex (why there should be any?, it is not the only East African techno-culture, nor the only group that shows indications of traveling to Arabia in the Abbassia Pluvial).
  5. Also it is “criticized” that the most comparable African culture, Howiesons Poort) is not recorded before c. 71 Ka BP (what IMO may indicate late cultural dispersals to Southern Africa from East Africa, for example, but, hey!, Mellars is fencing off balls like crazy at his conservative goal). 
  6. They find clear similitudes between Indian and African microlithic industries (apparently related to the development of “mode 4” in both areas, as well as in West Eurasia). Indian industries are dated to c. 38-40 Ka BP, while African ones are dated to c. 49 Ka BP (Kenya) or later. However West Eurasian ones have dates as old as 55 Ka BP (not for Mellars, who remains stuck in older date references which he describes as ∼40–45 ka [calibrated (cal.) before present (B.P.)]), what really suggest that we are talking here not of the “out of Africa” but of the West Eurasian colonization process (necessarily from further into Asia, genetic phylo-geographic structure demands) with offshoots to the nearby regions. 
  7. Another element of late Africa-India “similitude” they find is “the remarkable, double bounded criss-cross design incised on ostrich eggshell”, dated in India (Patne) to at least ∼30 ka (cal. B.P.), much earlier in South Africa. For Mellars this is beyond the range of either pure coincidence or entirely independent and remarkably convergent cultural evolutionary processes. Hmmm, really? Or are we before a clear case of wishful thinking as happens with the Solutrean-Clovis relationship hypothesis? Isn’t it 30 Ka BP anyhow well beyond any reasonable expectations for the OoA time frame, including Mellar’s own conjectures?
  8. Mellars accepts the paradox that the geographical limits of these highly distinctive microblade and geometric microlithic technologies are confined to the Indian subcontinent, with no currently documented traces of these technologies in regions farther to the east. And then makes up excuses for it, such as biological and cultural bottlenecks caused by “founder effects”, mysteriously leading to a loss or simplification of cultural and technological know-how, as well as fininding new and contrasting environments (in the same latitudes?!)
  9. Even in the case of Arabian colonization, Mellars shows to be in a very defensive attitude, admitting only to the reality of the Palestinian sites with clearly modern skulls, as well as to the area of Nubian Complex colonization (on whose peculiarities he insists a lot, as if it would be the only expression of the wider MSA techno-complex), disdaining all the other MSA colonization areas and, often ill-defined, variants.
In brief, for what I could see in the supplemental material, along with some potentially interesting references to the relative cultural community spanning from East Africa to South Asia at the time of emergence of “mode 4” industries, it seems that Mellars and allies are essentially putting the cart (their models) before the horses (the facts), what is bad science. 
In 2008, Zilhao and d’Errico angrily accused Mellars of being an obsolete armchair prehistorian (different words maybe, same idea). Back in the day I was tempted to support Mellars but nowadays I must agree that he is clearly stuck in a one-sided interpretation of prehistory whose time is long gone. Whatever the case I welcome the debate and can only hope that will help to produce even more evidence to further clarify the actual facts of the Prehistory of Humankind.