Showing posts with label anthropology. Show all posts
Showing posts with label anthropology. Show all posts

Sunday, November 19, 2017

Geology And Homo Sapiens Habitats Pleistocene Indian Subcontinent

Came across an interesting passage from this review paper:

Environments and Cultural Change in the Indian Subcontinent: Implications for the Dispersal of Homo sapiens in the Late Pleistocene - by James Blinkhorn and Michael D. Petraglia

Yet beyond relief, the geological structure of the Indian subcontinent plays another important role in patterns of habitability in the region. The analysis of the structure of geological basins within the Indian subcontinent led Korisettar (2007) to the conclusion that the Purana basins exerted a strong influence on hominin dispersals and occupation history. Although direct precipitation within the Purana basins is lower than other regions of the subcontinent, perennial supplies of freshwater are available because of spring activity from aquifers that deliver water resources from regions that receivemuch higher monsoonal precipitation.As a result of reliable water resources and abundant raw materials for stone tool manufacture, these geological basins are thought to have acted as refugia not only for hominin populations but also for varied flora and fauna (Korisettar 2007).

The importance of such Purana basins for providing refugia is well exemplified by the recent study of fauna from the Billasurgum caves, located within the Cuddapah Basin. Here, excavations revealed the first stratified sequence to document patterns of faunal occupation spanning the late Middle Pleistocene to Late Pleistocene (Roberts et al. 2014). This study illustrated the long-term continuity of large-bodied fauna within South Asia with only a single taxon of twenty-four identified as having gone extinct across the subcontinent (Roberts et al. 2014).


The "Purana" basins are Proterozoic in age. They are scattered all over Peninsular India. A common lithology is silica cemented sandstone or quartzite which forms prominent hill ranges, ridges and escarpments with ledges, overhangs and caves. These hard quartzites would have been one source of raw material for stone tools.  The rocks are also fractured and networks of pervasive cracks allow the storage and movement of groundwater.

The map (from a different paper) below shows the distribution of Middle Paleolithic sites (red dots) in India, Arabia and Eastern Africa. I have outlined in black (very approximate!) the location of three Purana basins. V stands for Vindhyan, C for Cuddapah and B&K for Bhima and Kaladgi.

 Modified from Huw S. Groucutt et.al. 2015

This paper have lots of information about climate change, ecology and stone tool record found in India. The authors discuss the Late Acheulean (130k - 100 K) ,  Middle  Paleolithic (94k - 34 K) and the Late Paleolithic ( < 45 K). These terms refer to particular styles of stone tool manufacture.

The India skeletal fossil record is very poor. However, based on comparisons with Middle Paleolithic of Africa and Homo sapiens fossils and tool associations in SE Asia and Australia, the authors are in favor of a wave of  Homo sapiens migrating into India as early or perhaps a little earlier than 100 k ago. This was followed by a later wave around 50 k years ago.  Do changes in cultural style and tool use point to changing populations.. with an intrusive population replacing an earlier one?.. that is an intriguing question. Some recent genetic work suggests that people from these earlier migrations died out without leaving a genetic legacy in us. All non African humans have descended from migrants who left Africa between 50K-80K years ago.  I had summarized these results in an earlier post on human population continuity in India.

See also other papers from this special volume of Current Anthropology on Human Colonization of Asia In the Late Pleistocene

Open Access.

Tuesday, August 15, 2017

Links: Human Evolution

Sharing links to interesting articles I have read in the past few months. Better understanding of human evolution is being driven by a) New fossil finds giving valuable insights into morphologic variation and geography, b) DNA analysis of both modern and extinct populations giving us an understanding of genealogical relationships and migration histories and c) better absolute dating of fossils that constraint evolutionary scenarios.

1) What Are Our Best Clues To The Evolution Of Fire-Making? Anthropologist Barbara J King examines the physical evidence of fire making by ancient hominins and presents speculations on how natural fires may have played a role in hominin cultural evolution.

2) A world map of Neanderthal and Denisovan ancestry in modern humans- Phys.Org. " There are certain classes of genes that modern humans inherited from the archaic humans with whom they interbred, which may have helped the modern humans to adapt to the new environments in which they arrived," says senior author David Reich, a geneticist at Harvard Medical School and the Broad Institute. "On the flip side, there was negative selection to systematically remove ancestry that may have been problematic from modern humans. We can document this removal over the 40,000 years since these admixtures occurred."

3) Three new discoveries in a month rock our African origins- Prof. John Hawks on new fossil dating of hominin fossils from Morocco and evidence from archaic DNA from S. Africa that complicates the African story of the origins of Homo sapiens. The scenario suggested here is that Homo sapiens did not evolve due to changes in a population which was genetically isolated from other Pleistocene African hominin groups. Rather there was a pan-African gene flow. This is multi-regionalism within Africa.

4) Out of North Africa- Dienekes argues the exact opposite.. that the Morocco fossils imply that Homo sapiens evolved in north Africa from a reproductively isolated population and that multi-regionalism is wrong.

5) Features of the Grecian ape raise questions about early hominins- Did the hominin clade evolve in Europe and not Africa? Prof. John Hawk's critique of a recent paper suggesting that view. He cautions that convergent evolution is common among different hominin lineages. A single feature, such as the mandible used in this paper, cannot indicate relationships.

6) Early modern humans in Sumatra before the Toba eruption- Steve Drury in Earth Pages summarizes new evidence that indicates early ( more than 70,000 years ago) migration of Homo sapiens into SE Asia. .." Together with the dating of the earliest Australians the Sumatran evidence is at odds with the view, widely held by palaeoanthropologists, that the ‘Out of Africa’ exodus began by crossing the Straits of Bab el Mandab between 74 and 58 ka when global sea-level fell markedly during marine oxygen-isotope Stage 4 (MIS4). A problem with that hypothesis has been that climatic and ecological conditions in southern Asia during MIS4 were unfavourable. But is seems that modern humans were already there and capable of adapting to both the climate shift and to the devastation undoubtedly caused by Toba."

Tuesday, November 29, 2016

Human Evolution: The Paleolithic In The Indian Subcontinent

Came across this article by anthropologist Sheila Mishra on the Paleolithic of the Indian subcontinent and its significance in understanding human evolution.

The Indian Subcontinent is one of the areas occupied by hominins since Early Pleistocene times. The Lower Palaeolithic in the Indian Subcontinent is exclusively Acheulian. This Acheulian is similiar to the African Acheulian and has been labeled "Large Flake Acheulian" (LFA). The Middle Palaeolithic in the Indian Subcontinent is a poorly defined entity and the author has suggested that this phase should be considered the final phase of the Large Flake Acheulian from which it evolved. Microblade technology has recently been shown to be older than 45 Ka in the Indian subcontinent and is certainly made by modern humans as it has a continuity from this time until the bronze age. Presently, the nature of the transition from Acheulian technology to Microblade technology is not well understood as few sites have been dated to the relevant time period.

The continuity of the Lower Palaeolithic in the Indian Subcontinent is due to its ecological features. The Indian Subcontinent extends from approximately 8°-30° N which would normally encompass equatorial, tropical and temperate latitudinal zones. However, the influence of the monsoonal climate and sheltering effect of the Himalayan mountains results in a sub-tropical grassland vegetation extending both northwards and southwards of its normal distribution. Rainfall, rather than temperature, is the most important ecological variable which has a longitudinal rather than latitudinal variation. Thus, the Indian Subcontinent has a more homogenous environment than any comparable landmass and one eminently suitable for hominins. In contrast, the African climate zones are strongly latitudinal in distribution. The Indian Subcontinent during the Early and Middle Pleistocene has close connections with Sundaland. The fauna associated with Homo erectus in Java is derived from the Indian Pinjor faunas. During low sea levels the area of land exposed in the Sunda shelf is equal in size to the Indian Subcontinent. Sundaland has an important buffering effect on the Indian Subcontinent, with favourable conditions for Hominins in Sundaland coinciding with unfavourable ones in the Indian Subcontinent.


She interprets the ecology and tool record as suggesting that Homo erectus evolved in the India-Sundaland region and not in Africa. This scenario implies there was a migration of Homo erectus into Africa from Asia by 1.8 million years ago or so.  She points out that a number of African mammal species appear in the Indian Siwaliks (Himalaya foothills)  by 3-2.5 million years ago and so presumably an ancestral species (Australopithecus? early Homo?)  may have migrated out of Africa at that time. There have been recent announcements of putative 2.6 million year old stone tools from the Siwaliks, but their significance is still up for debate. And given the paucity of skeletal remains in India, her theory is going to be a hard sell.

There is  also a really good description of the geological context in which Paleolithic stone tools are found in the Indian subcontinent. They have been often described as "surface" sites but Mishra points out that they have been eroding from fluvial sediments. Volcanism, sedimentation and tectonics in the African rift valley and parts of Java lead to conditions favoring both burial and preservation and later exhumation of fossils and tools. The situation in India is different. Since Mio-Pliocene most of Peninsuslar India has been an erosive landscape with sedimentation occurring in a few fluvial systems with a depositional regime. Thick fluvial successions are rare. Preservation potential on the Indian landscape was low. The implication is that India may have had a larger population of hominins through the Pleistocene than the rarity of remains suggest.  Caves are the other context in which hominin fossils have been found in Africa, Europe and Asia. Have caves been adequately explored in India?

A very interesting article. Open Access.

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.

One quibble 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!

Thursday, July 30, 2015

Amazonia Before Columbus

This is an interesting article published in the Royal Society's Proceedings B.

During the twentieth century, Amazonia was widely regarded as relatively pristine nature, little impacted by human history. This view remains popular despite mounting evidence of substantial human influence over millennial scales across the region. Here, we review the evidence of an anthropogenic Amazonia in response to claims of sparse populations across broad portions of the region. Amazonia was a major centre of crop domestication, with at least 83 native species containing populations domesticated to some degree. Plant domestication occurs in domesticated landscapes, including highly modified Amazonian dark earths (ADEs) associated with large settled populations and that may cover greater than 0.1% of the region. Populations and food production expanded rapidly within land management systems in the mid-Holocene, and complex societies expanded in resource-rich areas creating domesticated landscapes with profound impacts on local and regional ecology. ADE food production projections support estimates of at least eight million people in 1492. By this time, highly diverse regional systems had developed across Amazonia where subsistence resources were created with plant and landscape domestication, including earthworks. This review argues that the Amazonian anthrome was no less socio-culturally diverse or populous than other tropical forested areas of the world prior to European conquest.

I had read 1491 by Charles Mann so none of this came  as a surprise  to me. I would recommend Mann's book  too.  It is a very well researched richly detailed book on the human landscape of the America's (south and north) before the European conquest. The Amazon basin is covered too and the two things that stuck with me are the "anthrosols" or soils produced or rather enriched in organic matter and nutrients by humans activity like mulching and composting. The map below shows the distribution of these anthropogenic soils.



 Source: Clement C.  et.al. 2015

Their concentrations along the banks of rivers match early European descriptions of farming communities settled along river bluffs, with the interfluvial areas being occupied by semi-nomadic and nomadic hunter gatherers.

The other aspect that fascinated me was the observation of Europeans of the incredibly varied fruit trees from the Amazon jungles. Many true wild fruit are generally small, sour, bitter, thorny, spiky. The native people over millennia had transformed them by selective breeding into the edible fruit smorgasbord that one sees today. Imagine large areas of "virgin" Amazon forests were actually abandoned fruit orchards!

Read this article though.

Wednesday, May 16, 2012

Would It Matter Where You Placed The Anthropocene?

I have been listening to an absolutely riveting series of talks hosted at Generation Anthropocene. This is a project dreamed up by young Stanford University researchers and it involves interviewing scientists working on the broad theme of human impact on ecology and environment and consequentially the question of whether there is now a case to be made for defining a new geologic epoch called the Anthropocene.

The answers to where one would place the Holocene-Anthropocene boundary usually converges to either the beginning of Agriculture or the Industrial Revolution because both involve big changes to various aspects of the earth's environment. While these two, especially the Industrial Revolution, came through as a strong candidate, the most thought provoking answer was given by ... well off course .. a geologist... Jon Payne.

He suggested we take a methodological approach and understand how geological boundaries are defined. There has to be a distinctively recognizable sedimentary section which contains evidence of a faunal break i.e. a change in the earth's biota marked by the extinction of some species or the appearance of some new species.  We subdivide geologic time by recognizing that there has been some change in the earth's biota. Looking way back in the earth's past, sedimentary sections containing these transitions cover time periods well beyond the human time scale i.e. the sedimentary layers may represent a time passage of thousands of years.

Sediments usually accumulate in layers quite slowly over time periods longer than the scale of historical events. So, taking a long view, choosing as the beginning of the Anthropocene either the Industrial Revolution or World War II  won't matter, since all these events will collapse as one instance of sediment deposition. A geologist looking back several million years from now won't be able to discriminate events that took place a few tens of years apart.

In my opinion that doesn't make the concept of Anthropocene a useless exercise. For example, the boundary between the Pleistocene and the Holocene is defined by the disappearance of two foraminifera species and is dated as 10,000 BP radiocarbon years. These events mark a passage of few tens of years. Similarly,  today there would be sediment accumulating in a lake or a quiet deep sea that contains very thin layers that mark a sudden rise in a geochemical indicator of the Industrial Revolution or some other human activity.

We may mark that as a beginning of Anthropocene today. These deposits may even get preserved into the geological future. It's just that millions of years from now absolute dating methods like carbon14 that may discriminate events on the order of few tens of years will be useless on these deposits and the error bar on the dates obtained for these rocks will be on the order of hundreds to thousands of years. As a physical entity, the boundary in deep future may be recognizable as a sedimentary layer marking the disappearance of a significant number of species, although correlating that boundary with a specific historical event may not be possible.

Other talks that I liked were by Jon Christensen who talked about the myth of the American Frontier, Rodolfo Dirzo who talked about tropical biodiversity and Doug Bird who spoke about the native Martu peoples of Australia and their history of landscape management.

One refreshing aspect of these talks are that the hosts are all graduate students. What an opportunity to have an extended chat with your intellectual mentors and find inspiration in their work.

And who knows... start thinking of a career in science journalism.

Highly highly recommended.

Monday, May 14, 2012

Making Paleoanthropology A Real Science

There is a strengthening movement towards introducing more transparency in science by making data and papers produced from publicly funded research more readily available to all those interested. Paleoanthropology which includes the study of ancient human fossils has been an especially secretive field with researchers zealously guarding their fossils until they have completed their studies and published their results.

Kate Wong in Scientific American blog writes about recent efforts to end this culture of secrecy:

...Kivell thinks concerns about sharing fossil data are misplaced. “You don’t have to worry about getting scooped,” she says, explaining that a lot of the science of interpreting fossils lies in comparing them with other fossils, which is time-consuming work. “Good science in paleoanthropology is highly comparative, highly descriptive and cannot be done fast,” Hawks agrees. “If it’s not done with extensive comparison and careful description, it’s not going to be good.”

Hawks observes that genetics had the same problem paleoanthropology has with making data accessible. But eventually the geneticists “got over it as a culture.” Indeed, it has become standard practice among geneticists to upload new sequence data to a public database before submitting a paper on the findings to a journal for publication. “I really think most people want to see things more open than they are,” Hawks says. “[Paleoanthropology] should be a real science just like genetics is a real science.”