Environment History

Ancient DNA Offers Evidence Of A Perfect Storm Which Eradicated Ice Age Giants

ice age giants

Many giant Ice Age species have gone extinct by a perfect storm of a rapidly warming climate as well as humans. These species included elephant-sized sloths and massive sabre-toothed cats that roamed the windswept plains of Patagonia, southern South America.

Research led by the Australian centre for Ancient DNA (ACAD) at the University of Adelaide published their complete study in Science Advances journal. Their study revealed that it was only when the climate began to warm that the megafauna suddenly began to die off about 12,300 years ago. This was long after humans made their way to the area.

Both the exact timing and specific cause has long remained a mystery for centuries. Study leader, Professor Alan Cooper the ACAD Director, says Patagonia turns out to be the Rosetta Stone. It shows us that human colonization did not result in the extinction but only as long as it stayed cold. Instead, over 1,000 years of human occupation passed before a rapid warming event began to take place, and then the megafauna were extinct within less than a hundred years.

partial jaw
Partial jaw of a giant, extinct jaguar that was discovered in a cave in the Ultima Esperanza region of Patagonia. (Image credit: Fabiana Martin/CEHA)

Researchers studied DNA that had been extracted from radiocarbon-dated bones and teeth that were discovered in caves across Patagonia and Tierra del Fuego. The findings were used to trace the genetic history of the populations. Species including the South American horse, giant jaguar, sabre-toothed cat and the massive one-ton short-faced bear were found widely across Patagonia but seemed to disappear a short period after humans began exploring the area.

The pattern of increasingly fast human colonization 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.

Professor Chris Turney from the University of New South Wales says the America’s are unique in that humans moved through two continents, from Alaska to Patagonia, in a mere 1,500 years. As they did this, they passed through distinctly different climate states (warm in the norm and cold in the south). Because of this, we can contrast human impacts under the different climatic conditions.

guanaco jawbone
Ancient guanaco jawbone along with a tooth sample used to extract DNA, primarily excavated from Cueva del Mylodon. (Image credit: Alan Cooper/Malmo Museum)

The only big species that was able to survive were the ancestors of today’s llama and alpaca (known as the guanaco and vicuna) and even these species almost went extinct during the time period.

Lead author of the study Dr. Jessica Metcalf from the University of Colorado Boulder says the ancient genetic data shows that only the late arrival in Patagonia of a population of guanacos from the north saved the species, all other populations became extinct.

Dr. Fabiana Martin from the University of Magallanes says 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. It seems appropriate that we are now using the bones from that area to reveal the key role of climate warming, and humans, in the megafaunal extinctions.