Tuesday, February 6, 2018

Some Thoughts On The Middle Paleolithic Stone Tools From India Story

Early Middle Palaeolithic culture in India around 385–172 ka reframes Out of Africa models - Kumar Akhilesh, Shanti Pappu, Haresh M. Rajapara, Yanni Gunnell, Anil D. Shukla and Ashok K. Singhvi

From a site in Tamil Nadu, South India, stone tool types named Levallois were dated to be 385 ka -172 ka (ka-thousand years). Levallois tools are made by striking a stone core to produce smaller flakes which are then put to various uses.  They were more versatile than the older clunkier hand axes. Previous estimates for the arrival of this technology in India was thought to be around 125 ka or later, introduced by migrating Homo sapiens.

So, who made these older Levallois tools? The recent finding from Morocco of Homo sapiens like fossils dated to be older than 300 ka has prompted many to interpret this finding as evidence of an early arrival of Homo sapiens into south Asia.

Some thoughts-

1) this discovery has put a rare spotlight on the Indian hominin record. The paucity of hominin skeletal fossils and a lack of a rigorous chronology for deposits and tools have meant that the Indian record, if not ignored, has received less attention. This study has established a robust chronological framework of the sedimentary sequence in which these tools are found. A change from older Acheulean style tools to Levallois styles is documented within this dated sequence. Finding a trend, something changing or being replaced by something else, at one locality and within one sedimentary sequence is rare at hominin sites across the world. I think this make it more a compelling story than an isolated find of some stone tools.

2) I've noticed that some media article headlines and discussions in social media are suggesting that the "Out of Africa" theory needs to be reassessed. Well, what exactly do you mean by 'Out of Africa'? The original and popular Out Of Africa theory proposes that Homo sapiens originated in Africa around 200 ka. Then, 60ka-50ka ago these modern Africans migrated and settled the globe, replacing earlier archaic human populations. But, it is not news that there have been many 'Out of Africa's'.  By that I mean there have been many dispersals of humans out of Africa. Early archaic Homo dispersals occurred by 1.8 mya. The ancestors of Neanderthals and Denisovans left Africa by 1 mya to 700 ka ago.  There is genetic, fossil and archaeological evidence for a Homo sapiens migration around 65-50 ka ago. There is also evidence of an earlier migration of Homo sapiens (dated to ~120 ka) into the Levant and possibly into south Asia as well. An older Homo sapiens fossil dated to 185 ka has been found recently in Israel. Now, this discovery of  advanced tool technology has been interpreted by some to indicate an even earlier migration of Homo sapiens into India.

To me, the bigger evolving story is that Homo sapiens are getting older and older, originating earlier that 385 ka! That they might have dispersed into Asia soon after is less of a surprise. Migrations out of Africa seem to have occurred again and again, and so another at around 385 ka doesn't seem to be an extraordinary event. There would have been back migrations into Africa as well. I suspect that the recent finding of anatomically modern humans in Morocco dated to more than 300 ka has shaped the media narrative of this stone tool finding into an 'early migration into India' story.

How would have these stone tools been interpreted without supportive fossil evidence that Homo sapiens existing by 385 ka?  There always was an alternative hypothesis that proposed that evolution of complex behavior and associated advances in tool technology took place independently in disparate human populations residing in Africa, Europe and Asia.  Aspects of 'modern' anatomy and behavior might have developed multiple times in different places.  In this context, the hominin skull dated to around 236 ka found in the Narmada valley, Central India, is intriguing. Given its antiquity, the reasonable interpretation is that it represents a population descended from an earlier Homo erectus migration into India. Yet, it has a mix of archaic and derived (modern) features. It's estimated cranial capacity is comparable to modern humans.  Is it an example of  parallel evolution of 'modern' traits outside Africa?  Or, does it represent a hybrid population formed by the mixing of archaic hominins and Homo sapiens?

Skeptics like Michael Petraglia have pointed out that the technological transition seen in India may be a local invention of technology and not due to migration of a new population carrying advanced tools. Changing environmental conditions may have spurred similar inventions in different parts of the world.

3) One point to note is whether these earlier archaics and Homo sapiens living outside Africa contributed ancestry to today's people. Some recent genetic analyses suggests that all non-Africans are descended from Homo sapiens that dispersed from Africa around 80 ka -50 ka ago. These people did mix with archaic hominins in Europe and Asia but the degree of admixture is low. We contain about 2-4% Neanderthal and/or Denisovan genes.  If this is true, if earlier people migrating from Africa did not leave much of a genetic legacy in us, then the original 'Out of Africa' model still has some relevance.


  1. Thank you Suvrat! This is fascinating. I could go with parallel evolution of modern traits...

    1. Yeah, these were closely related lineages. so just putting it out as a possibility :)

  2. Hi Suvrat, really fascinating post. Your last para suggests more than just 'some relevance' for the Out-of-Africa model. My knowledge of genetics isn't extensive, but isn't the genetic diversity for all non-African Homo sapiens quite low compared to Africans? To me, this suggests that the rest of us (non-African sapiens) are descendants of a small ancestral population that left Africa via the Levant and Middle East. Timing that departure is another matter entirely, and as you say, there have probably been multiple such migrations from Africa.

    The other question I have is that how do you know that the Levallois tools are of sapien origin? Could they not be Homo erectus? I recall reading that there is some evidence of Homo erectus tools in Jwalapuram, Andhra Pradesh around the time of the Toba eruption 74,000 years ago.

    While we're on the topic, do you have suggestions of books to read about this subject? I'm fascinated by ancient human migrations, currently reading Guns, Germs, and Steel by Jared Diamond. The sad thing is that the book has very little to say about South Asia, and this was true of Sapiens by Yuval Noah Harari as well. Not sure why though.

    1. Navaneethan- I agree. Most of the non-African ancestry can be traced to a small population of Homo sapiens which migrated 70-60 thousand years ago. We have small amounts of admixture from Neanderthals and Denisovans. What is often not appreciated due to our focus on the global story is that the story within Africa is more complex with different lineages of Homo sapiens differentiating and persisting and admixing with archaics. That story is being slowly unraveled. Regarding Levallois, I think there is no agreement that there were made exclusively by Homo sapiens. From what I have read they have been found associated with archaic humans as well. There is quite a bit of controversy regarding the Jwalapuram tools. Some archaeologists are convinced they show similarity to the Nubian style tools made by Homo sapiens. Others think they were made by an earlier archaic population.

      Regarding books, there is nothing comprehensive about South Asia. One problem is lack of a skeletal fossil record. A general book on human evolution I can recommend is Lone Survivors by Chris Stringer. I have some review articles on recent findings on human migrations. If you are interested I could email these to you..let me know. thanks for reading.