/* */ Rosa Rubicondior: Late Persistence of Human Ancestors at a Site in India.

Friday, 8 October 2021

Late Persistence of Human Ancestors at a Site in India.

Map illustrating the location of the study site, Singi Talav, in relation to the world’s youngest Acheulean sites from other key regions. Made with Natural Earth: Free vector and raster map data at naturalearthdata.com.

© Jimbob Blinkhorn
Late Persistence of Human Ancestors at the Margins of the Monsoon in India | Max Planck Institute for the Science of Human History

More evidence published recently that an archaic hominin spread far and wide out of Africa into Eurasia, many thousands of years before Homo sapiens migrated out of Africa.

This evidence is from the youngest Acheulean site so far discovered, at Singi Talav, in the Thar Desert, Rajasthan, India, dated to 177,000 years ago. This shows that stone tools were used there for over 1 million years and may have persisted until the arrival of H. sapiens. This stone tool-making technology is believed to have arisen in Africa about 1.5 million years ago and reached India, presumably by being taken there by migrants, about 1.2 million years ago.

This new dating was done by researchers led by Dr. James Blinkhorn of the Max Planck Institute for the Science of Human History. According to to their news release:
A handaxe from the Thar Desert, where Acheulean populations persisted until at least 177 thousand years ago.
© Jimbob Blinkhorn
The timing and route of the earliest expansions of our own species across Asia have been the focus of considerable debate but a growing body of evidence indicates Homo sapiens interacted with numerous populations of our closest evolutionary cousins. Identifying where these different populations met is critical to revealing the human and cultural landscape encountered by the earliest members of our species to expand beyond Africa. Although fossils of ancient human populations are extremely rare in South Asia, changes in the stone tool kits they made, used, and left behind can help resolve when and where these encounters may have occurred.

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In a paper published in Scientific Reports, an international team of researchers led by the Max Planck Institute for the Science of Human History report the relatively recent occupation of the site of Singi Talav (Rajasthan, India) by Acheulean populations up to 177,000 years ago (Figure 2). The site was once thought to be amongst the oldest Acheulean sites in India, but now appears to be one of the youngest. Indeed, these dates show the persistence of Acheulean populations in the Thar Desert after their disappearance in eastern Africa around 214,000 years ago and Arabia 190,000 years ago. This result supports the late persistence of Acheulean populations in India, where previous research has shown their presence as recently as 130,000 years ago.

The site of Singi Talav, set on a lakeside close to the modern town of Didwana at the edge of the Thar Desert, was first excavated in the early 1980's, revealing multiple stone tool assemblages (Figure 3). The largest assemblage shows a focus on the production of stone handaxes and cleavers that are typical of the Acheulean. However, the techniques needed to accurately date these assemblages were not available at the time of their discovery. Since then, a range of sites have been examined that constrain the chronology of
The lakeside setting has ideal preservation conditions for an archaeological site, enabling us to return 30 years after the first excavation and readily re-identify the main occupation horizons again. We've applied a range of modern methods to re-examine this critical site, including new approaches to directly date the occupation horizons and to reveal the vegetation in the landscape that Acheulean populations inhabited.

This supports evidence from across the region indicating that India hosted the youngest populations using Acheulean toolkits across the world. Critically, the late persistence of the Acheulean at Singi Talav and elsewhere in India directly precedes evidence for the appearance of our own species, Homo sapiens, as they expanded across Asia.
Dr Jimbob Blinkhorn, Lead author
Max Planck Institute for the Science of Human History
Acheulean occupations in India, but the ecological settings of the sites remains poorly known.

[…]

The researchers used luminescence methods to directly date the sediment horizons occupied by ancient human populations. These methods rely on the ability of minerals like quartz and feldspar to store and release energy induced by natural radioactivity, allowing scientists to determine the last time sediments were exposed to light.

[…]

The Thar Desert likely presented a key ecological frontier for expanding populations of Homo sapiens moving eastwards as they first met the Indian monsoon system. The results of this study suggest that this may have also been a demographic and behavioural frontier - a potential zone in which Homo sapiens encountered another, closely related, human population.
This is the first time the ecology of an Acheulean site in India has been studied using these methods, revealing the broader character of the landscape that these populations inhabited. The results from the two methods we applied complement each other to reveal a landscape rich in the types of grasses that flourish during periods with enhanced summer monsoons.

Professor Hema Achyuthan, co-author
Anna University, Chennai, India
The open access paper can be read in Scientific Reports:
Abstract
South Asia hosts the world’s youngest Acheulean sites, with dated records typically restricted to sub-humid landscapes. The Thar Desert marks a major adaptive boundary between monsoonal Asia to the east and the Saharo-Arabian desert belt to the west, making it a key threshold to examine patterns of hominin ecological adaptation and its impacts on patterns of behaviour, demography and dispersal. Here, we investigate Palaeolithic occupations at the western margin of the South Asian monsoon at Singi Talav, undertaking new chronometric, sedimentological and palaeoecological studies of Acheulean and Middle Palaeolithic occupation horizons. We constrain occupations of the site between 248 and 65 thousand years ago. This presents the first direct palaeoecological evidence for landscapes occupied by South Asian Acheulean-producing populations, most notably in the main occupation horizon dating to 177 thousand years ago. Our results illustrate the potential role of the Thar Desert as an ecological, and demographic, frontier to Palaeolithic populations.

This tentative circumstantial evidence that anatomically modern humans could have come into contact with archaic hominins who had migrated out of Africa much earlier in our evolutionary history, is one possible explanation for the appearance of Denisovan, and other unidentified DNA in several populations in south and southeast Asia, Australasia and Melanesia, since Denisovans, like Neanderthals, are probably descendants of these early migrants in Eurasia, while H. sapiens are descendants of those who remained in Africa, making Neanderthals and Denisovans a sister, or possibly a cousin species to H. sapiens.

It's not yet known who exactly made the stone tools and other artifacts at this site in India but the possibility is that they were H. erectus or their immediate descendants. Yet more evidence of the emerging picture of modern human evolution by hybridization with other contemporary hominins, much in the way ring species behave, where evolutionary divergence had not progressed enough to create full barriers to hybridization so genes were able to flow between related species.

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