Wednesday, March 23, 2016

In Search Of Early Humans In India

I attended a talk yesterday by Prof. S. N Rajguru on the evidence for early hominins in India. This was part of the C. Meenakshi Memorial Lecture series hosted by the Bhandarkar Oriental Research Institute in Pune.

Prof. Rajguru is an acknowledged expert on Quaternary geology and paleoclimates of the Indian subcontinent and the talk followed the contours of his expertise.

Here is the abstract which was given to us:

In Search of an "Early Man" (>2.5 Ma yrs to around 50 Ka yrs) in India

Recent progress in absolute dating methods, in understanding palaeo-landscape of India in light of behavior of monsoonal rainfall in the last 10 million years (Ma), fluctuations in sea level on 7500 km, long coastline of India and the rise of Himalayas and Tibetan plateau from 1000 m during the Late Miocene (around 15 Ma yrs ago) to around 3000 m during early Pleistocene(~1 Ma yrs ago) have added new information on chronology and environment of "Early Man" (hominin) in India.

It is now know that the Indian monsoon is at least 10 Ma old and was fairly strong till 2 Ma yrs. It started fluctuating (strong, moderate, weak) during the Pleistocene (2.5 Ma-10 Ka). The Indian monsoon was relatively strong to moderate during early Pleistocene (2.5 Ma - 0.7 Ma), moderate to weak during middle Pleistocene (0.7 Ma- 130 Ka) and weak during the late Pleistocene (130 Ka- 10 Ka).

Owing to changes in the strength of monsoonal rainfall the landscape of India also responded dramatically. The sea level went down by 100 to 150 m below the present sea level around 18 Ka BP (before present) and was high around 125 Ka BP by 5 to 7 m in tectonically stable part of coastal India. The peninsular rivers also responded to climatic changes in terms of strong erosion and excess deposition. The Himalaya was affected by tectonic movements and by glaical and interglacial climates which were part of global climatic changes during the Pleistocene.

These environmental changes did affect the biological world including 'hominins' in India.  It appears that early man was present in the foothills of the Himalayas in NW India around 2.6 Ma yrs BP and around 1.7 Ma BP in the coastal parts near Chennai in Tamil  Nadu. These two important discoveries in the form of stone tools and bones with cut marks made by early man raise doubts about the 'out of Africa' migration of early man in Asia during the early Pleistocene.

We are not certain who was the maker of stone tools like choppers around 2.6 Ma yrs or little  earlier in the foothills of the Himalayas near Chandigarh. Most likely he belongs to "Australopithicus" group of hominin. On the other hand 'Homo erectus' was responsible for making Acheulian (Lower Paleolithic) artifacts, like handaxes, cleavers, etc., around Chennai during the early Pleistocene (~ 1.7 Ma).

There is a long gap between 'Homo erectus' (~1.7 Ma, with brain capacity of 800 to 1100 cc) and modern man or Homo sapien sapiens (with brain capacity of 1100-1300cc) who had his origin in Africa 200,000 yrs BP.

In Indian context, there are large number of Lower Paleolithic sites well preserved in varieties of environment during the middle Pleistocene (0.7 Ma- 130 Ka). There is a cultural change in the form of stone tools consisting of small size scrapers, points, choppers, etc., made on flakes removed from cryptocrystalline minerals like chert and chalcedony. It is as yet not clear whether the maker of Middle Pleistocene artifacts was 'Modern Man' who arrived in India via West Asia, or he still belongs to advanced form of ' Homo erectus'. Excepting a single fossil skull of hominin, dated to around 250 Ka yrs in the Central Narmada Basin, we do not have any other human fossil data of early late Pleistocene (~ 100 Ka BP).  Thus, the search for early man, though shrouded in scientific controversy, will continue in future in old Himalayas, warm peninsula and in humid coastal strip of India.

A couple of quibbles. I'm sure he didn't mean it, but it sounds like changes in monsoonal strength led to a lowering of sea level around 20K- 18 K years ago. This is not true. The sea level dropped because sea water was locked in high latitude continental ice sheets during the Last Glacial Maximum.

Secondly is the comment that evidence of putative 2.6 million year old stone tools from the Siwalik foothills of the Himalaya raises doubt about the 'Out of Africa' migration of early humans into Asia in early Pleistocene. I really don't see how this is so. Unless you are claiming that bipedalism and hominins originated in Asia, a position for which there is not an iota of evidence, all this discovery does (and the finding is still being debated) is deepen the timeline of the earliest migration of hominins from Africa into Asia.

I came across the same argument in a more detailed article about the Siwalik stone tools and scratch marks on bovine bones discovery in Outlook magazine. That article went even further and stated that this 2.6 million year old tools and bone marking may tell us "when we started looking and behaving more like Homo sapiens rather than apes" Huh!... How so? How does an unconfirmed find of possible Early Pleistocene tools in India  signal the evolution  of Homo sapiens from ape like ancestors? The mere presence of these archaic tools can't be a signal. If so, the same reasoning applies to the Pleistocene tool record in Europe and China too. So, such a broad overreaching claim explains nothing.  It is just sensational journalism by Outlook magazine.

I don't want to dwell on this issue too much since it was not the thrust of Prof.  Rajguru's talk. Instead, he gave quite an engrossing presentation with lots of pictures of the various field sites where stone tools ranging in age from 1.7 million years to 50 thousand years or so have been found. He spoke in detail about the paleo-environments and it is clear that humans in India occupied a wide range of landscapes and ecology during the Pleistocene. There were some awesome sites in Ladakh in the Himalayas, a few sites along the Gujarat coast associated with mid-late Pleistocene aeolian carbonate sand made up of Miliolite shells (great cross bedding), and a very interesting site closer to Pune. This was in a laterite cave in a sea cliff overlooking the Arabian sea near the town of Guhaghar. Tools provisionally dated to about a hundred thousand years old or so have been found there.

What did come out of this talk was some of the limitations faced by researchers in India. The first is the lack of a skeletal record of humans. We have just a few skeletal fragments from the Narmada valley. I asked Prof. Rajguru about this lack of bones. He suggested that the African record is richer in bones because of preservation in volcanic ash and fine river muds and sands. In contrast, most of the sites where stone tools have been found in India are surface sites where the preservation potential of skeletal material is poor. That does point the way to a future program of more focused search for bones in the Pleistocene sediments across India. The second problem is establishing absolute chronology. Dating methods are very expensive and until recently Indian researchers could afford to date only the occasional sample. Or, they had to rely on collaboration with western (and Australian) researchers. Hopefully this will change in the future.

Prof. Rajguru is a field geologist. He must be in this seventies now but his enthusiasm for field work is still undiminished. He kept stressing the importance of understanding the geology, stratigraphy and paleo-ecology of human habitation sites to fully understand the significance and variability of human occupation in India in terms of past climates and landscapes. Even without skeletal material one can make a useful contribution toward understanding human evolution....

having said that.. we do need to find more bones!

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