- Researchers conjecture that the Todas, an indigenous tribe residing in the upper Nilgiris, may have moved up the mountains with their buffalo herds in response to climate change 3500 years ago. The research predates their origin by at least 1500 years as held by historical records.
- The inference of Todas’ arrival in the upper Nilgiris 3500 years ago is based on reconstructing the Sandynallah basin’s paleoecology in the region. The reconstruction points to the presence of fire, humans, herbivores, and grasslands 3500 years ago.
- The research suggests that environmental conditions (an arid climate with a weak summer monsoon) 3500 years ago would have favoured wildfires. The Todas, numbering only 1500 today, are known to manage the high-altitude grasslands with fires.
- The evidence opens up interdisciplinary fields of paleoecology, archaeology, and human ecology of the montane Nilgiris and the broader region of peninsular India.
Climate change in peninsular India may have pushed a pastoralist community, most likely the Todas, and their buffalo herds, to the highest elevations of the Nilgiris in the Western Ghats, at least 1500 years before what historical accounts assume, a research has claimed.
Todas are one of the six indigenous tribes inhabiting the high mountains of the Nilgiris in the Western Ghats. The Todas are a Particularly Vulnerable Tribal Group with around 1500 members. Based mainly on the Toda language’s linguistic affinities with the common Dravidian languages of southern India, it has been suggested or even assumed that the Toda origin in the Nilgiris is not more than 2000 years old.
However, scientists at the Indian Institute of Science, Bengaluru and Inter-University Accelerator Centre, New Delhi, conjecture that the discovery of evidence of “intense fire activity”, along with signs of the presence of humans, herbivores, and grasslands in the Sandynallah basin in the upper Nilgiris in the Western Ghats 3500 years ago is indicative of the movement of a pastoralist community along with their herds from a lower to the cooler higher realms to cope with the prevailing arid climate.
The research can be accessed in bioRxiv, a preprint server for biology. bioRxiv (pronounced “bio-archive”) is a free online archive and distribution service for unpublished preprints in the life sciences. This research has not yet been peer-reviewed.
The Nilgiris is also home to six ancient indigenous communities and tribes – Badagas (traditionally settled agriculturists and the largest numerically), Todas (pastoralists occupying the upper plateau), Kotas (artisans) and Irulas, Kurumbas and Paniyars (hunter-gatherers, who also practice settled agriculture now).
“The Todas are a current-day pastoralist community who worship the buffaloes they keep; their cattle are central to their culture. They are known to manage the high-altitude grasslands with fires, and hence their ways of land-use formed one of the earliest reasons behind the debate that grasslands were anthropogenic. There is no known history of the Toda arrival and settlement,” said Ramya Bala Prabhakaran at IISc’s Centre for Earth Sciences, Centre for Ecological Sciences, and Divecha Centre for Climate Change.
“Hence, we propose that this pastoralist community in our sediment record may have been the Todas. It is conjectural; we do not show cultural evidence for this,” Ramya Bala told Mongabay-India. The study, said the authors, provides “compelling evidence” for the presence of people and livestock at Sandynallah in the higher elevations of the Nilgiris at 3500 years ago coinciding with or subsequent to a “changed climate and environment” in peninsular India.
The Nilgiris are among the highest mountains in the long Western Ghats mountain chain, with peaks and plateaus ranging from 1700-2600 metres. The mountain tops were originally covered in vast rolling grasslands, with clumps of stunted evergreen trees called sholas in the middle because of these altitudes. The grassland-shola combination unique to the Western Ghats’ higher reaches is considered to be more than 20,000 years old. Today, Toda buffalos are restricted to small patches of grasslands behind Toda settlements and often wander around Ooty town. Also, the tribe, distributed across a few hamlets in the upper Nilgiris mainly practice settled agriculture, growing “English vegetables” like carrots, potato and cabbage.
Reconstruction of Sandynallah’s paleoecology
Describing the study’s motivation, Ramya Bala said they intended to look at patterns of burning in the past since the presence of grasslands in the shola-grassland mosaic has been debated since 1938 with many suggesting that grasslands here are a product of anthropogenic clearance of forests. “Paleoecology investigations using pollen had shown that grasslands were indeed ancient (at least 35000 yrs old), predating human arrival in this region. We were more interested in what fires (both human and natural) did to these grasslands, and so we looked at fires and their relationships with vegetation,” she said.
Co-author Sarath Kavil, at IISc’s Centre for Ecological Sciences, observed that the Todas need grasslands for their buffalo herds, and if there aren’t grasslands, they create grasslands by burning. “We don’t know for sure how the fire originated 3500 years ago. As you go up, the forest would be more favoured. But the Todas would need grasslands for their buffalo herds. So as the pastoralists moved upwards to cope with the climate to cooler reaches, they may have set fire to the forest patch so grasslands would emerge next year in natural succession. The immediate solution (to create grasslands) is to burn a patch of forest,” Sarath said.
Researchers reconstructed fire history, animal abundance, and human presence in the Nilgiris using radiocarbon-dated peat samples from the Sandynallah basin that lies 2200 metres above sea level in the Nilgiri hills in the state of Tamil Nadu.
An array of tools was used to reveal the region’s paleoecology: charcoal and pollen abundance to trace fire history and draw inferences on its possible relationship to past climate and human activity; fungal spores associated with dung to assess animal abundance, lipid steroid biomarkers (associated with faeces) extracted from peat helped decipher the presence of domestic livestock and human populations in the Nilgiri plateau; n-alkane signatures shed light on vegetation history these natural montane forest-grassland mosaics and aided comparison to previous paleoecological studies from the region.
The charcoal record indicated fires 22000 years ago and an intense fire 3500 years ago. Coprophilous fungal spores (spores of fungi associated with dung) of the taxa Sporormiella spp., Sordaria spp., Delitschia spp., and Trichodelitschia spp. were found in the peat samples at different depths. These are generally considered as reliable indicators of pastoralism. n-alkane signatures (most widely used terrestrial plant biomarkers) point to prevalence of dry arid conditions and dominant grassy vegetation in the region. The research suggests that environmental conditions 3500 years ago would have been favourable for wildfires.
Grasslands, fire, humans, domestic herbivores 3500 years ago in the upper Nilgiris
Sarath explained that 20,000 to 30,000 years ago (during the Last Glacial Maximum, a period in Earth’s history when ice sheets were at their greatest extent) and 3500 years ago, the climate of the region was arid and the Indian summer (southwest) monsoon had also weakened during this period (including in the northern and central Western Ghats). These conditions may have bolstered the vegetation’s flammability, including forest patches in the montane Nilgiris, as seen in other tropical regions.
“The arid climate favoured grasslands to flourish in the Nilgiris region. This has been established from other studies. There is no evidence as such from the region, but modern humans are known to occupy the region only 10000 years ago, which leads us to believe the source of the fire 22000 years ago was natural. However, the intense fire activity 3500 years may have been linked to a pastoralist community. We do not know for sure. But at this point, we find evidence of fire, grasslands, humans, and herbivores. So the Todas appear to be the most likely candidate,” hypothesised Sarath referring to the two fire activity signatures 22000 and 3500 years ago.
What led the researchers to infer that the humans in the upper Nilgiris were pastoralists in the first place?
Sterols are diagnostic of human presence 3500 yrs ago in the upper Nilgiris, said Ramya Bala, and the co-presence of increased coprophilous fungal spores and sterols with a bovine signature indicates the presence of domestic cattle. Hence this must have been a pastoralist community, she emphasised. This layer (in the peat sample) also shows a big peak of charcoal abundance, clearly indicating fires’ co-occurrence.
“Whether or not the fires were anthropogenic (human-caused), we cannot say, since the natural climatic signal seems to indicate an arid period (possibility of natural ignition). But given that humans are known to have knowledge of fire-ignition and control, it is possible that the pastoralist community used fires to maintain the landscape for their cattle,” she said.
Additionally, the analysis of coprophilous fungal spores and herbivore sterol biomarkers points to a ‘corralled herd of domestic herbivores’ in the upper Nilgiris.
“We analyse the possibility that the increase in coprophilous fungal spores and herbivore sterol biomarkers may have come from increases in the wild animal population. But since the grassland expansion seems to have started many centuries or millennia before this fire horizon, the wild animals had a long duration in which to migrate to this new grassy niche,” said Ramya Bala.
“It would be extremely serendipitous for wild animal migration to coincide with human presence in an area. Hence we conclude that the 5-fold increase in fungal spores is due to a concentrated presence of herbivores that co-existed with the humans, which leads to this interpretation of a corralled herd of domestic herbivores. The statement is conjectural; we do not show any cultural evidence for the same such as would be seen in archeological studies,” she said.
Need for further research and excavations
The evidence also opens up interdisciplinary fields of paleoecology, archaeology, and human ecology during mid-to-late Holocene for further investigation in the montane Nilgiris and the broader region of peninsular India. Holocene refers to the latest geologic time interval, covering approximately the last 11,700 years of Earth’s history.
One significant aspect of the work was the use of sterol signatures (in a Swedish collaboration) to identify humans and specific animals’ presence.
“n-alkanes are powerful diagnostic tools of vegetation types since woody vegetation, aquatic plants, and grasses are supposed to show specific easily differentiable signatures. Sterols are unique chemical diagnostic tools to identify presence of humans and certain animals, widely employed by archeologists. Sterols and n-alkanes share the same initial steps of extractions, which is why we decided to invest in both. Sterols are not done in India; we got a rare opportunity to analyse our samples through a collaboration in Sweden. We were lucky to get sterol analysis,” observed Ramya Bala.
It is of course entirely possible that the people and livestock recorded 3500 years go represent an unknown tribe or even a failed immigration, the researchers caution.
“Sandynallah valley hosts very old peat accumulations and has been central to the reconstruction of paleovegetation in the montane Nilgiris, Western Ghats. The site is a treasure trove for paleoclimatic reconstruction and evidence for humans’ presence 3500 years ago calls for further additional archaeological excavations. It’s hard to suggest how modern Todas might react, and they are already quite restricted in population and are quite different from how they were in the past,” added Sarath.
Banner image: The Sandynallah valley where the team did its sampling. Photo by Sarath Kavil.