Although human hunting played a part in the demise of the woolly mammoth about 10,000 years ago, homo sapiens were but bit players in a global drama involving climate change, comet impact and a multitude of other factors, scientists have found in separate studies.
Previous research had blamed their demise on tribal hunting. But new findings "pretty much dispel the idea of any one factor, any one event, as dooming the mammoths," said Glen MacDonald, a researcher and geographer at the University of California in Los Angeles, to LiveScience.com.
In other words, hunting didn’t help, but it was not instrumental. The ancestors didn’t do it.
So what did? After thriving for 250,000 years, the huge mammals lingered on in dwarf form in the Arctic Ocean’s Wrangel Island until 3,700 years ago. Between 20,000 and 25,000 years ago, LiveScience said, the animals declined during the worst of the last major ice age, though they started to multiply in warmer interior Siberia.
Analyzing samples from more than 1,300 woolly mammoths as well as 450 pieces of wood, 600 archeological sites and upwards of 650 bog lands in Beringia—the former land bridge under the Bering Strait, thought to be the giant mammoths’ last habitat—a team led by MacDonald discovered a host of things working against them.
The beasts were felled by a combination of declining food supply and terrain that deteriorated into peatlands, all brought on by warming climate, said the study as quoted in USA Today. Grasses and willow, mammoths’ normal food, was replaced by poisonous birch to eat, and solid ground gave way to wetlands more difficult to tread upon, USA Today said.
“Pressure from hunting was also present, as contemporary Paleolithic sites are numerous in both Siberia and now in northwestern North America,” the study said. “Modeling studies show that given the environmental stresses at the time, even limited hunting by humans could have significantly contributed to woolly mammoth extinction."
Together these factors conspired to push the mammoth population down further, MacDonald said.
"Mammoths faced profound climate change and very profound changes in their habitat and landscape, and also faced pressure from humans," MacDonald told LiveScience, adding that such changes have implications for current climate issues.
"Now think about the twenty-first century, where we're seeing rapid climate change, massive changes in the landscape and certainly pressure from humans on the environment," he said. "Species today are facing the same sorts of challenges the mammoths did, but the rate of those changes today are much greater than what mammoths faced."
Compounding these influences was the apparent impact of a comet or meteor that splintered in Earth’s atmosphere about 12,900 years ago and sparked the 1,300-year-long Younger Dryas period. Another study, published in this week’s Proceedings of the National Academy of Sciences, posits that a comet or meteor impact did indeed prompt this ice age and spell the beginning of the final end for our shaggy friends.
The international research team included another California scientist, James Kennett of the University of California at Santa Barbara. Researchers analyzed deeply buried, melted glass in Pennsylvania, South Carolina and Syria to determine that it could only have been formed during a high impact. The team said that it would have taken temperatures of 3,100 to 3,600 degrees Fahrenheit to create such glass formations, according to The Los Angeles Times.
“The evidence of impact, the team said, now covers at least a third of the planet, ranging from California to Western Europe and the Middle East,” the newspaper reported. Such extraterrestrial-impact theories have sparked controversy in the past, but the study’s authors said that only a massive impact could have plunged the glass so deeply into the Earth.
The existence of multiple locations, combined with those temperatures, “indicates that the meteor or comet that struck the Earth broke up during its entry to the atmosphere and struck at multiple locations,” the Los Angeles Times said. “The team has yet to identify a limit to the debris field.”