Latest revision as of 09:38, 13 December 2020

[edit] History

[edit] Megafauna coexisted with humans for 30,000 years

Chandrima Banerjee, December 10, 2020: The Times of India

About 1,00,000 years ago, megabeasts started disappearing from the face of the planet — the 13-ton elephant ancestor Stegodon, the 600-kg lizard-like Megalania, the 100-kg Giant Beaver. It was a period of significant climate change. It was also when prehistoric humans started expanding their footprint outside Africa. Wherever humans arrived, large animals died out. But not in Africa and south Asia.

It’s a pattern that has puzzled palaeontologists for decades. But while Africa has been studied for six decades, India has never been. In a new study, for the first time, researchers from Yale University, the Smithsonian’s National Museum of Natural History, the University of Nebraska and the George Mason University have compiled a database of recent fossils from the Indian subcontinent to fill this gap.

Lead author Dr Advait Jukar said “co-evolution” has been used to explain the survival of large animals in Africa. “It’s kind of like an evolutionary rat race, where one species has to be better than the other to survive,” Jukar told TOI. So, if humans got better at hunting, animals would get better at escaping. If humans lived in riverine plains, animals would move into the safety of dense forests. The theory worked for Africa but India remained a mystery. Because there had never been a comprehensive study of Indian fossil records. So, Jukar documented the extinction of five large mammals — two massive elephant relatives (Palaeoloxodon namadicus and Stegodon namadicus), a prehistoric hippo (Hexaprotodon), a wild zebra-like horse (Equus namadicus), and the wild ancestor of the modern domestic Zebu cattle (Bos namadicus) — on the Indian subcontinent. If the extinction pattern could be demystified, it would help understand why large animals are found in such abundance in India.

With fossil records from 25 sites in India and statistical analysis, they found that the disappearance of large animals here began some 30,000 years ago. Humans had started arriving from Africa about 60,000 years ago. So, there is a 30,000-year gap between the appearance of humans and (limited) disappearance of megafauna.

This is around the time that there was a drop in the Indian Monsoon.

Yet, they noted, “all of the species we document going extinct survive several intervals of prolonged drought during the late Pleistocene (126,000 to 12,000 years ago).” The only clear link, it turns out, is with the time humans start using projectile tools, which made hunting more efficient.

So, only four mammal species went extinct over the past 50,000 years in India while 114 survived. It’s the third slowest extinction rate after eastern Africa (eight extinct, 473 surviving) and southern Africa (seven extinct, 265 surviving).

Four factors may have helped the survival rate. Jukar said India has been home to different species of humans, with a record going back almost 2 million years. “This would have led to coevolution, just like in Africa.” Prehistoric humans here hunted small prey. Then, about 9,000 years ago, cattle domestication began. Finally, the large geographic area over which animals were distributed may have helped support populations.

“We have a fossil record in Siwalik, which goes back about 24 million years. The only other places where we get comparable records are North America and parts of China. But in India, research has been held back because of a lack of resources,” he said.