April 10, 2014
Studies of fossils and soil samples collected at a site in South India have revealed unique attributes of the ecosystem not found in many parts of the world. In particular, an international team of scientists found that most mammalian species in the region seem to have survived at least 100,000 years in conditions that could have pushed them to extinction in Europe or the Americas.
Their research, for the first time, reports on dated and stratified deposits of mammalian fauna in the Indian subcontinent over the last 200,000 years. In addition, “one of the most significant findings is that a variety of mammals survived through major fluctuations of climate in the past,” said Michael Petraglia, one of the authors of the study published in Proceedings of the National Academy of Sciences in the week of April 7.
Apart from climactic changes, the Indian subcontinent was also subjected to the devastating Toba volcanic super-eruption 75,000 years ago as well as increasing numbers of humans in the last 10,000 years. Mammals in the subcontinent, however, survived almost unchanged because they had access to a unique range of ecosystems to inhabit. Meanwhile, those in many other parts of the world were becoming extinct in large numbers. The difference lay in the nature of their habitats.
The configuration of geographic landmarks and monsoon patterns “has given rise to a network of ecosystems like the coastal mangrove, evergreen upland western and eastern ghats, deciduous forest, semi-arid inland regions, the Thar desert and plains of the Indus and Ganga,” explained Dr. Ravi Korisettar. “Between the Vindhyas in the north and the Nilgiris in the south, the Deccan Plateau has preserved a variety of these ecosystems suitable for habitation since prehistoric times.”
Dr. Korisettar is the Dr. D.C. Pavate Professor of Art and Archaeology, Karnatak University, Dharwad, and a member of the team that conducted the study.
It found that the variety of ecological settings available for habitation as well as their interconnected nature were essential for the continued existence of mammals. “The mosaic of habitats allows for the presence of a diverse range of species, whereas the connection between these habitats allows animals to migrate between them as the climate changes,” said Dr. Petraglia, of the Research Laboratory for Archaeology and the History of Art, University of Oxford, UK.
Their findings are consistent with fossil records from around South Asia, and with parts of tropical Africa.
Both these scientists were part of a team that studied samples collected from the Billasurgam cave complex in the Kurnool district of Andhra Pradesh, a state in southern India. The site was chosen because investigations in the 1970s had found that many animal fossils and archaeological deposits were present there.
Describing their findings, Dr. Korisettar said they’d found “11 families and 26 genera of birds, mammals and amphibians. There were antelopes, gazelles, horses, pigs, primates, rhinoceroses, rabbits, and evidence of crocodile amphibians.” The samples were then studied using optically stimulated luminescence to discern their ages and characteristics. With the exception of one primate – identified in the paper as Theropithecus cf gelada – all other mammalian taxa, or population groups, survive in the subcontinent to this day.
However, even as Dr. Korisettar remarks, “Conserve the habitats, the rest will take care of itself”, the quality of the mammals’ survival these days is deteriorating. One of the suggested causes for extinction of fauna in other parts of the world in the last 1,000 centuries was over-hunting by early humans. An analogous threat has come to modern India after all these years of resilient survival: anthropogenic climate change.
Is a mutually beneficial coexistence possible once again?
“Climate change, in combination with the dramatic increases in human populations in the last 10,000 years in India, may be leading to decline of certain animals, restricting them to smaller geographic ranges,” Dr. Petraglia said. For example, the Kaziranga National Park in northeast India hosts two thirds of the world’s population of Great One-horned Rhinoceroses, an animal whose habitat may once have spread farther south.
But whatever has been pushing them over the brink, mammalian conservation efforts in India may now find it essential to not just preserve habitats but also their inter-connected nature in the subcontinent. Moreover, Dr. Petraglia suggested that the Billasurgam caves also be protected against economic development in the region, especially mining activities. “The caves should be considered for national protection owing to their fascinating history of research and the significance of their deposits for future research,” he said.