New York, June 19 (IANS): Researchers have found that a perfect storm of a rapidly warming climate and human activities killed giant Ice Age species including elephant-sized sloth and powerful sabre-toothed cats that once roamed the plains of Patagonia.

Human activity that gradually lead to the warming of climate caused the extinction of the megafauna around 12,300 years ago, said the researchers.

"The study shows that human colonisation didn't immediately result in extinctions, but only as long as it stayed cold," said lead researcher Alan Cooper, professor at the University of Adelaide in Australia.

Species such as the South American horse, giant jaguar and sabre-toothed cat, and the enormous one-tonne short-faced bear (the largest land-based mammalian carnivore) were found widely across the South American country of Patagonia, but seemed to disappear shortly after humans arrived.

The pattern of rapid human colonisation through the Americas, coinciding with contrasting temperature trends in each continent, allowed the researchers to disentangle the relative impact of human arrival and climate change.

"More than 1,000 years of human occupation passed before a rapid warming event occurred, and then the megafauna were extinct within a hundred years," Cooper added in the paper published in the journal Science Advances.

The only large species to survive were the ancestors of present day llama and alpaca, the researchers said.

"The ancient genetic data show that only the late arrival in Patagonia of a population of guanacos from the north saved the species, all other populations became extinct," explained Jessica Metcalf from the University of Colorado-Boulder, in the US.

"In 1936 Fell's cave, a small rock shelter in Patagonia, was the first site in the world to show that humans had hunted Ice Age megafauna. So it seems appropriate that we're now using the bones from the area to reveal the key role of climate warming, and humans, in the megafaunal extinctions," noted Fabiana Martin from University of Magallanes in Chile.

The team studied ancient DNA extracted from radiocarbon-dated bones and teeth found in caves across Patagonia, and Tierra del Fuego, to trace the genetic history of the populations.