Ancient humans not to blame for mass island extinction

An international research team has debunked a popular theory that ancient humans caused mass animal and plant extinctions on newly inhabited islands.

Archaeologists and palaeontologists, including from Griffith University and The Australian National University (ANU), compared records of human arrival and extinctions on islands spanning the past 2.6 million years, finding little overlap between the two events.

Co-researcher and ANU Professor Sue O’Connor said the evidence did not reveal early modern humans to be the destructive agents that “they’re often portrayed to be”.

“Human arrival had minimal impacts on biodiversity loss,” Professor O’Connor said.

“Our research shows that causing mass extinctions has not always been part of the human story. We shouldn’t see extinctions as inevitable.”

Lead researcher Associate Professor Julien Louys from Griffith University said the work challenges the notion that these ancient people caused “untold amounts of damage” to ecosystems.

“We found that this was only the case for the most recent human arrivals on islands, in the past few thousand years,” Associate Professor Louys said.

“Based on classic cases of island extinction from the more recent past, we expected that mass extinction should shortly follow island colonisation. However, when we examined the data, there were very few cases where this could be demonstrated.

“Even in cases where there was a close link between human arrival and island extinctions, these could not be disentangled from records of environmental change brought about by global climatic events and changing sea levels.”

Professor O’Connor said the team also recorded several examples of human ancestor extinctions and instances where humans had to abandon islands.

“The unique ecological conditions that drive island extinctions definitely didn’t spare humans either,” she said.

“Island ecosystems are some of the most at risk in the world today and understanding the past impacts of people on these environments is critical for safeguarding them into the future.”

“We show that the successful colonisation of islands does not necessarily require wholesale destruction of ecosystems,” Associate Professor Louys said.

“By studying the cases where people lived on islands for thousands of years without tipping these fragile ecosystems off balance, we might gain valuable insights into how they can be better managed today.”

The research is published in Proceedings of National Academy of Sciences.

Professor O’Connor’s Australian Research Council Laureate Fellowship supported the research, which involved other ANU researchers Professor Philip Piper, Dr Shimona Kealy and Dr Stuart Hawkins.

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