The Late Pleistocene was an unfortunate time for Australia’s largest marsupials, reptiles, and birds – known as megafauna. By 40,000 years ago, around 65 percent of these creatures were extinct.
Researchers have spent decades debating whether climate change, humans, a combination of both or something else entirely was the cause of megafauna demise.
But a new study published in the journal Archaeology in Oceania has found that we might have been a bit premature deciding that megafauna had disappeared by 40,000 years ago in all areas.
A team including Flinders University in Adelaide and Australian National University researchers, used new dating methods and analysis to discover that, in a forest in the highlands of Papua New Guinea, at what’s known as the Nombe rockshelter site, megafauna survived much longer, even with humans making occasional visits.
In particular, the researchers found in this small oasis, two species of kangaroo that could have survived 20,000 years ago.
“Although it is often assumed that all of the megafaunal species in Australia and New Guinea became extinct coast to coast by 40,000 years ago, this generalisation is not based on very much actual evidence,” says Professor Gavin Prideaux, from the Flinders University Palaeontology Laboratory.
“It is probably more harmful than helpful in resolving exactly what happened to the dozens of large mammals, birds and reptiles that were living on the continent when people first arrived.”
The team undertook new analysis on multiple bone fragments from Nombe rockshelter. This site had both human and animal remains. The palaeontology team at Flinders University was given the animal bones to see if they could confirm the species.
“That’s how we got involved – because our expertise is in identifying megafauna and bone chunks,” Prideaux told Cosmos.
They discovered that the thylacine, and an extinct four-legged marsupial (Hulitherium tomasettii) still lived in the PNG Highlands when people first arrived, possibly around 60,000 years ago.
“About 20 to 40,000 years ago, the forest was a bit colder, and the tree line was considerably lower,” one of the researchers, palaeontologist Isaac Kerr, told Cosmos.
“You get the denser, dumpy animals showing up there. They’re living in a really dense forest and they need to stay warm.”
Even more surprising, two large extinct kangaroo species – one which bounded on four legs rather than hopping (Protemnodon tumbuna) and one yet unconfirmed as a species, but which could be the kangaroo Protemnodon nombe – might have survived up to 20,000 years ago.
But that’s not to say that humans wouldn’t have had an effect in most areas. Using pollen analysis to confirm, the team suggests that the reason why these creatures survived as long as they did is because humans seemed to only visit the area infrequently.
“If these megafaunal species did indeed survive in the PNG Highlands for much longer than their Australian equivalents, then it may have been because people only visited the Nombe area infrequently and in low numbers, until after 20,000 years ago,” says ANU Professor Tim Denham.
The Nombe rockshelter was first excavated by archaeologists in the 1960s, but the most intensive phase of fieldwork was conducted in 1971 and 1980 by ANU archaeologist Dr Mary-Jane Mountain, who is an author on the new paper.
Mountain’s research yielded the first detailed description and interpretation of the Nombe site and played a pivotal role in shaping our understanding of the human history of the PNG Highlands. The fossils used in the current analysis were all discovered in the 1970s and 80s.
This new research backs up previous findings from Kangaroo Island, which also discovered that megafaunal kangaroos may have persisted to around 20,000 years ago in some of the less accessible areas on the island.
Jacinta Bowler is a science journalist at Cosmos. They have a undergraduate degree in genetics and journalism from the University of Queensland and have been published in the Best Australian Science Writing 2022.
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