Climate change drove one of the last surviving woolly mammoth populations to extinction less than 6,000 years ago, meaning the animals may have been alive around the time Newgrange was built.
That's according to a research team led by Russell Graham of Pennsylvania State University which studied the presence of mammoths on St Paul Island, Alaska in the Bering Sea
The island supported a large group of the animals for thousands of years after they went extinct in Asia and North America.
No humans were a party to the demise of this iconic ice age species. Rather, they were overcome by climate change, the researchers say.
The woolly mammoth disappeared from its mainland haunts between 14,000 and 10,500 years ago, the researchers say. Human predation and a warming climate are often proposed as drivers for the animal’s extinction.
Smaller populations did manage to survive on small islands that used to be part of the land bridge connecting Asia and North America. Rising sea levels would have swamped the land bridge and isolated populations that persisted as sea level rose at the end of the last ice age.
Dr Graham and colleagues provide a detailed look at one such group living on St Paul Island. The island provided a "rare opportunity" to study the rise and fall of an isolated population in the absence of human influence, the authors say in a report published on Monday in the US Proceedings of the National Academy of Sciences.
They found that woolly mammoths survived on St Paul until about 5,600 years ago. Compare this to the building of the Newgrange passage grave about 5,215 years ago. The question was what caused their final extinction.
There was no evidence for human involvement as there were no remains indicating human habitation and the first recorded landing on the island was in 1787 made by Russian whalers.
Nor can a lack of food be blamed for the animal’s disappearance given a plentiful supply of vegetation, so neither human inerferrence nor food shortages were “extinction drivers”, the researchers say.
“Instead the extinction coincided with declining freshwater resources and drier climates between 7,850 and 5,600 years ago,” they say.
Water supplies slowly declined, even as sea level continued to rise as the ice left by the ice age began to melt.
This left the existing mammoths with less room on the already compact 110 square kilometre island.
The research team used five independent indicators to time the final extinction and used sedimentary cores and other measures to support their theory.
The animals died out “because of the synergistic effects of shrinking island area and freshwater scarcity caused by rising sea levels and regional climate change”, the authors write.
The demise of the St Paul mammoths resonates as human-induced climate change proceeds today. It underscores “the vulnerability of small island populations to environmental change, even in the absence of human influence” the authors write.
