Fossil evidence shows that some pretty massive beasts roamed what we now call Patagonia 13,000 years ago – giant sloths, 12-foot-tall bears, saber-tooth tigers and more. Just 1,000 years later, they were all extinct. What happened? New evidence shows that humans hunted these prehistoric creatures to extinction … with a little help from climate change.
Humans had traversed South America and were already living in what are now parts of Chile and Argentina 13,000 years ago, according to a new study led by Professor Alan Cooper, director of the University of Adelaide’s Australian Centre for Ancient DNA (ACAD). However, it appears that humans and the local giants were able to co-exist for 500 years. The reason? A cold climate.
The Americas are unique in that humans moved through two continents, from Alaska to Patagonia, in just 1,500 years. As they did so they passed through distinctly different climate states – warm in the north and cold in the south. As a result, we can contrast human impacts under different climate conditions.
Study co-author Professor Chris Turney of University of New South Wales and the team analyzed DNA radiocarbon-dated bones from caves in Patagonia and Tierra del Fuego. Species included the South American horse, llama, giant sloth, giant jaguar, sabre-toothed tiger and the short-faced (but really heavy – one ton – and really tall – 12 foot) bear, which was the largest land-based mammalian carnivore. What they found is that a climate warming occurred about 500 years after humans arrived and that all of the giants but the llamas and alpacas were extinct within 100 years. The cause was not solely one or the other but a perfect storm of both.
Cooper says the warmer temperatures caused droughts that decimated the plains where many of these animals roamed and stimulated the growth of the forests that they were less suited for. On the other hand, the warm climate allowed humans to hunt for longer periods, which allowed them to kill and eat more animals, which allowed them to become bigger and better hunters, which allowed them to … you get the idea. In less than a century, humans with arrows and spears killed every large Patagonian to extinction except for llamas and alpacas.
Less than 100 years to extinction. Elizabeth Jeffers from Oxford University says this about that.
The evidence from the fossil record demonstrates the rapidity with which extinctions can occur and ecosystems can collapse when species are squeezed by multiple stressors that limit their ability to track habitat changes. These processes—rapid climate warming and habitat fragmentation by humans—are occurring today.
Cooper had this one last comment about warmer temperatures and humans.
Warming might be the magic ingredient that activates or accelerates our natural destructive tendencies. Or cold shuts us down.