“Our study uses a clear predictive test to assess two opposing hypotheses about large animals in ancient and modern tundra ecosystems: that the animals disappeared before the shrubs increased, or that the shrubs increased before the animals disappeared,” said Professor Mary Edwards of the University of Southampton who was part of the study team.ĭr Ali Monteath, the lead author from the Universities of Alberta and Southampton, adds “The results support the idea that at the end of the last ice age a major shift to warmer and wetter conditions transformed the landscape in a way that was highly unfavourable to the animals, including mammoths”. Their results showed that willow and birch shrubs began to expand across Alaska and Yukon around 14,000 years ago, when records of dated bones indicate that large grazing mammals were still abundant on the landscape. They then compared this with how the numbers of radiocarbon-dated bones from horse, bison, mammoth and moose changed through time – which provided them with an estimate of their changing population sizes. By focusing on records that met strict dating criteria the team could accurately pinpoint the timing of shrub expansion across this region. To test these alternative hypotheses, an international research team examined records of fossil pollen preserved in lake sediments across Alaska and Yukon for thousands of years. Others advocate that climate change drove the vegetation and landscape changes, and these led to the loss of the animals as their habitat disappeared. This is because low-growing vegetation exposes the ground to colder conditions than shrub cover does, and thus the ground and the carbon it contains remain well frozen. It is now popular to advocate that a form of rewilding - where animals are returned to their original ecosystems to restore more “natural” conditions - might reverse the trend of increasing shrub cover, with possible benefit of keeping carbon stored in the ground. Today, with strong arctic warming, shrubs are spreading even further north into tundra regions. These ancient coincidences have led to the suggestion that human hunting caused the demise of the mammals, and their loss led to the shrub expansion, as they were not there to trample down the vegetation and put nutrients back into the soil. At the same time, several iconic mammal species that inhabited what is now Alaska and the Yukon, such as the woolly mammoth, became extinct, and archaeology records human presence in the region. The findings, published in the journal PNAS, have major implications for proposals to prevent the soils in the Arctic today from thawing by re-introducing animals such as bison and horses.Ībout 14,000 years ago, at the end of the last ice age, open, grassy landscapes that had extended eastwards from France across the now submerged Bering Sea all the way to the Yukon in Canada were transformed by the rapid spread of shrubs. Credit Duane FroeseĪ new study has shed new light on why large mammals died out at the end of the ice age, suggesting their extinction was caused by a warming climate and expansion of vegetation that created unsuitable habitat for the animals. “It was surreal to sit in the British Library and slowly work out what people 20,000 years ago were saying but the hours of hard work were certainly worth it.Published: 5 January 2022 Bison Image. “The meaning of the markings within these drawings has always intrigued me so I set about trying to decode them, using a similar approach that others took to understanding an early form of Greek text,” he told the BBC. The research paper by Bacon, Freeth, and University of Durham professors Paul Pettitt and Robert Kentridge, as well as independent researchers Azadeh Khatiri and James Palmer, was published on January 5 in the Cambridge Archaeological Journal.īacon said he used information and images of cave art publicly available online and through the British library to collect data and look for repeating patterns. This discovery predates other systems of record-keeping by at least 10,000 years. The research team compared the birth cycles of modern versions of the animals with the number of marks to determine that they referenced a lunar calendar and tracked reproductive cycles. “I was stunned when Ben came to me with his underlying idea that the numbers of spots or lines on the animals represented the lunar month of key events in the animals’ life-cycles,” Freeth told the BBC. University College London honorary professor Tony Freeth was one of the experts Bacon consulted about his theory and became a research partner. 57,000-Year-Old Neanderthal Markings Identified in a Sealed French Cave, New Research Finds
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