Advent of stone microblades set off ancient population boom in Indian subcontinent

The easy-to-manufacture tools - also known as microliths - were a vast improvement over larger stone flake tools used previously, according to Michael Petraglia, an archaeologist at the University of Oxford, UK, who led the study.

Because microblades could be cut from stone more quickly and in higher volumes than flakes, hunting probably became a vastly more efficient endeavour.

"It allows people to more reliably and more cheaply slaughter animals," Lawrence Guy Straus, a paleoanthropologist at the University of New Mexico in Albuquerque, told New Scientist.

Petraglia and his colleagues contend that the beginnings of a global ice age pushed ancient populations of Indians into closer contact - and competition - with one another.

"They need to develop new strategies to produce new resources. They invent microlithic technology and it spreads very rapidly," said Petraglia.

Petraglia's team argue that genetic, environmental and archaeological records make a strong circumstantial case for their theory.

Between 30 and 35,000 years ago, the Earth cooled dramatically.

In Europe, these changes brought with them massive glaciers, pushing Neanderthals and newly arrived humans into small pockets, and perhaps contact.

In India, however, this ice age shortened the monsoon season and transformed what had been a rather homogenous tropical landscape into a patchwork of savannahs and deciduous forests bordered by desert, according to Petraglia.

"When you get more deserts, you're getting environmental fragmentation. That is conducive to hunter-gatherers," Petraglia said. "They like mosaic environments because you tend to have a lot of diversity in flora and fauna," he added.

"These changes almost certainly would have split up ancient populations, but they could have spurred their growth as well," Petraglia said.

By treating the mitochondrial DNA of contemporary Indians as a sort of molecular clock, the researchers documented an expansion in Indian genetic diversity dated to around the time of this ice age.

This is where microblades come in handy. The tools - narrow and up to 4 centimetres long - began appearing in large numbers around 30,000 years ago, archaeological records from across the subcontinent show.

Prior to this, Indians wielded bulkier, less-efficient stone flakes.

"Microblades, which were probably attached to spears and later arrows, were a game-changing technology that allowed more densely packed hunter-gatherers to thrive," Petraglia said.

"It's a mystery why there are so many people in that part of the world and it wasn't just domestication that led to more than a billion people being around in South Asia. We argue that is has to go back to a much earlier period," said Petraglia. (ANI)

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