Early Humans Did Not Cause Island Extinctions, According to New Study

by AMNH on

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Islands are particularly prone to widespread extinction of plants and animals. Over the last few thousand years, much of the blame for these losses is generally attributed to human activities. But the first global assessment of the possible link between the arrival of early humans and close human ancestors on islands and island extinction shows that was not always the case.

Rendering of a dwarf elephant next to a fallow deer; the top of the elephant's head does not even reach the deer's shoulder.
Dwarf elephants, which lived on several Mediterranean islands, died out after modern human arrival. For scale, the extant male fallow deer pictured with the elephant is about 1 m (40 inches) tall at the shoulder.
P. Schouten/R. MacPhee / ©AMNH

“Prior to migration of modern Homo sapiens across the planet, other populations and species of hominins lived on a number of the world’s islands,” said Ross MacPhee, senior curator in the Museum’s Department of Mammalogy and a co-author on the new study, published today in the journal Proceedings of the National Academy of Sciences.  “Evidence that these earlier humans caused appreciable losses is mostly poor to nonexistent, which suggests that it was deleterious cultural practices—overhunting, excessive resource exploitation—of modern humans that were behind later insular extinctions.”

The research team, led by scientists at Griffith University in Australia, examined archaeological and paleontological records of the more than 30 islands known to be inhabited by humans between about 2.6 million and 11,700 years ago, ranging from modern-day Britain, Ireland, and Cyprus to Taiwan, Okinawa, and Tasmania. They found very little overlap between human arrival and extinctions.

“Based on classic cases of island extinction from the more recent past, we expected that mass extinction should shortly follow island colonization. However, when we examined the data, there were very few cases where this could be demonstrated,” said Griffith University Associate Professor Julien Louys, the lead author of the study. “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.”

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.

“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,” said Louys.