Sept. 13 (UPI) -- Based on an analysis of elephant birds' bones, scientists now believe humans arrived on the tropical island of Madagascar off the coast of Africa more than 6,000 years earlier than previously thought.
Scientists led by the Zoological Society of London used radiocarbon dating techniques to place the age on extinct Madagascan elephant birds, which show cut marks and depression fractures consistent with hunting and butchery by prehistoric humans. Their findings were published Wednesday in the journal Science Advances.
The Aepyornis and Mullerornis species were about 10 feet tall and weighed 770 to 1,100 pounds -- among the largest birds ever to inhabit Earth.
"This new discovery turns our idea of the first human arrivals on its head," co-author Dr. Patricia Wright, an anthropologist from Stony Brook University, said in a press release. "We know that at the end of the Ice Age, when humans were only using stone tools, there were a group of humans that arrived on Madagascar. We do not know the origin of these people and won't until we find further archaeological evidence, but we know there is no evidence of their genes in modern populations."
So she asks: "Who these people were? And when and why did they disappear?"
In previous research, humans were believed to first arrive in Madagascar 2,400-4,000 years ago. according to an analysis of lemur bones and archaeological artifacts.
The Zoological Society of London scientists now peg the time as far back as 10,500 years ago.
"We already know that Madagascar's megafauna -- elephant birds, hippos, giant tortoises and giant lemurs -- became extinct less than 1,000 years ago," lead author Dr James Hansford, from ZSL's Institute of Zoology, said in a press release. "There are a number of theories about why this occurred, but the extent of human involvement hasn't been clear."
Hansford said "a radically different extinction theory is required" to figure out the extinctions on the island.
"Humans seem to have coexisted with elephant birds and other now-extinct species for over 9,000 years, apparently with limited negative impact on biodiversity for most of this period, which offers new insights for conservation today," he said.
The bones were originally found in 2009 in Christmas River in south-central Madagascar.
A fossil "bone bed" containing many ancient animal remains was possibly a major kill site, the researchers said.