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Thanks a lot to Ibra (and Manjunat, who is the original source, it seems) for sending me a copy of Petraglia's last paper, that otherwise should be publicly available in six months.
The research actually has two parts that somehow Petraglia wants to fuse: genetics and archaeology. I forewarn that I do not agree, on first read, with the genetic interpretation and that petraglia himself is an archaeologist, not a geneticist. There are important geneticists in the team though, like Toomas Kivisild and Mait Metspalu.
Genetics
In any case, I fail to see how from the referenced genetic papers, the most recent one being Sun 2005, they conclude that South Asian M sublineages expanded so late. This must be inspired by a recent paper that did suggest a late expansion for SA M sublineages in comparison to the East, paper that I did not pay really any attention because it was behind a paywall. I can't even recall the authors (though guess it's from the Estonian team, considering its influence on this one).
I must note here that these estimates are contradictory with the model proposed by Atkinson 2007, that suggests that South Asia was already experiencing high and continuous demic expansion rates already since 55-50,000 BP.
Archaeology
The really important part, the one that takes most of the space and really provides important data, is the archaeological section, including a very interesting reconstruction of the climate and vegetation of South Asia some 30,000 years ago.
But the real substance is in the lithic sequences of the Jurreru Valley (Jwalapuram, Andra Pradesh, Southern India), where we can witness the following:
1. There is apparent human presence since c. 74,000 BP (also before, from Petraglia's older work in the same area). These people already used stone blades, characteristic of the UP cultures in West Eurasia (and in some East Asian cases too).
2. The existence of microblades (microliths) can be dated safely to at least 38,000 BP, though they do not become the dominant type of tool until c. 34.000 BP, when the presence of microblade cores is clear indication that they were made intentionally and not just by accident.
Other sites researched are:
Patna (Maharashtra Pradesh), where an ostrich egg-shell gave a radiocarbon date of c. 30,000 BP. Here flake blades are found since the early (>30 kya) stages, though the technology is described as being Middle Paleolithic. A trend towards microlithism is also detected since c. 30,000 BP.
A series of sites in Western Sri Lanka (Sabaragamuva province), dated from 38-36,000 BP to 28.500 BP, that have also yielded some microblade technology. These caves also provided the earliest known Homo sapiens remains of South Asia.
Southern Sri Lankan sites, Bundala and Patirajevala, show an early MP technlogy TL-dated since 70-64,400 BP, showing a gradual reduction of size of the artifacts. In the upper layer (dated to c. 28.500 BP) there is a clear change towards geometric microlithism.
Hence it seems reasonably clear that microlithic technology seems to have expanded from southern India and maybe Western Sri Lanka, where it may have begun as early as c. 38,000 BP (uncalibrated, should be before 40 kya after calibration), with strong signs of quotidiain usage c. 35,000 BP, and is found at Patna (a reference for possible expansion into other West and Central Eurasian regions), c. 30,000 BP (uncalibrated too).
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6 comments:
I was behind a firewall too, credit to Manju for getting us the paper.
Paywall (i.e. you must pay if you want it). Firewall is something different: protects your PC from hijacking.
But fair enough, cheers to Manjunat too. :)
“Paywall (i.e. you must pay if you want it). Firewall is something different: protects your PC from hijacking.”
That is too specific a definition for a firewall. A Paywall is a more general type of firewall. A firewall simply blocks unauthorized acess but permits authorized access; the term has been commercialized by companies that promote protection from virus and spyware etc. PNAS has the policy of being open access to certain countries and excluding other. You can bypass their system by using an Asian proxy.
“I must note here that these estimates are contradictory with the model proposed by Atkinson 2007, that suggests that South Asia was already experiencing high and continuous demic expansion rates already since 55-50,000 BP.”
Atkinson et al. mentioned that they linearly scaled their data to haplogroup Q assuming that Q had to be 45kyr. Every region has it own unique population history and Q might not be that old. Growth in the Americas starts at 18 suggesting that the Q date might be over estimated.
You can bypass their system by using an Asian proxy.
Really? O_O
Atkinson et al. mentioned that they linearly scaled their data to haplogroup Q assuming that Q had to be 45kyr. Every region has it own unique population history and Q might not be that old. Growth in the Americas starts at 18 suggesting that the Q date might be over estimated.
He deals with mtDNA only. He means Papuan mtDNA Q. ;)
For IE go:
Tools >Internet Options>Connections
Click LAN Settings, Click use Proxy Server for your Lan
ie.
221.215.72.218:8080
Address: 221.215.72.218
Port: 8080
This is a proxy list:
http://www.samair.ru/proxy/proxy-01.htm
Not all proxies are going to work, in that case you need a proxy tester.
http://www.checker.freeproxy.ru/checker/
“He deals with mtDNA only. He means Papuan mtDNA Q”
Yes that’s what I mean. He scales the dates to mtDNA Oceanic clade Q which is assumed to be 45kyr but might actually be more like 38kyr. Here is the quote.
“In order to plot population size with respect to time, it was necessary to calibrate rates of molecular evolution. Recent evidence of systematic variation in observed rates of molecular evolution through time (Ho et al. 2005 ) suggests that rates should be calibrated using divergence events of a similar time depth to the timescale of interest. For this reason, an internal rate calibration was used. Rates were fixed to 1.691 x 10–8 substitutions/site/year, based on a 45-kya age for haplotype Q in New Guinea. Haplogroup Q occurs at high frequencies only in New Guinea (parts of Melanesia have a closely related subtype [Q2], which also occurs at very low frequencies in Micronesia and Polynesia, probably as a result of more recent admixture [Friedlaender et al. 2005 ]). This is consistent with archaeological evidence for modern human arrival on the super continent Sahul (comprising what is now New Guinea and Australia) by approximately 42–45 kya (O'Connell and Allen 2004 ). In order to isolate uncertainty in the coalescent process and facilitate regional comparison, uncertainty in the calibration time itself was not incorporated into our analyses. Inferred times do, however, scale linearly with respect to the rate calibration, such that if, for example, a 50-kya age for the New Guinea clade were assumed, the timescale would be increased by approximately 11%.”
I thought you meant American (and other) Y-DNA Q.
I agree that all age estimations depend on the calibration you use and that is always a risky choice. That's (partly) why I treat age estimates with little or even no respect.
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