A DNA study rewrites the history of koalas, finding that their decline began 100,000 years ago, before humans arrived
Researchers have generally accepted the narrative of humans contributing to the decline of koala numbers in Australia.
While habitat destruction and urbanization have certainly accelerated species loss, new genetic evidence points to a much earlier tipping point. Rather than starting with the arrival of humans, the decline appears to have begun about 100,000 years ago, when koalas were already entering a major population collapse.
What happened?
Earth.com I mentioned Researchers at Sydney University and Texas A&M University have mapped the history of the koala population over the past nearly 100,000 years and That’s it It is climate shifts – not early human activity – that caused the first major collapse of this species. The work was published in the journal Molecular Biology and Evolution.
The researchers first measured how often new mutations emerged within four koala family lines by comparing parents and offspring. With this rate determined, they applied it to 457 koala genomes to infer past population changes.
What emerged was a long decline: numbers began declining about 100,000 years ago, and bottomed out about 60,000 years ago, in the last ice age. Drought conditions across Australia separated the western and eastern koalas, and evidence suggests that only remnants of the eastern koala persisted, later giving rise to the five east coast populations that exist today.
“The study rewrites the timeline of the genetic history of koalas in Australia,” said Toby Kovacs, a PhD student at the University of Sydney who led the research, according to Earth.com.
Why does it matter?
This discovery changes how conservationists understand the risks koalas face. If koalas have indeed survived a severe climate-induced bottleneck, their DNA could help show how much resilience remains — and how little room there is for additional stress from habitat destruction, disease, and fires.
Koalas are part of local ecosystems and economies linked to biodiversity and Tourism. When forests are fragmented or lost, neighboring communities can also face increased land degradation and increased risks of wildfires.
Better genetic tracking could help officials intervene early, before the population shrinks dramatically and inbreeding makes recovery more difficult.
Kovacs explained it this way: “Estimating the mutation rate improves our ability to reconstruct koala population history, understand their ability to adapt, and make more informed conservation decisions in the future.”
What do people say?
Kovacs stressed that the new research does not absolve modern society of responsibility for the threats koalas face today.
“It is important to clarify that many of the threats facing modern koala populations are caused by humans, including habitat loss and hunting,” he told Earth.com.
“Surviving koalas are again seeing a similar decline, but this time due to human-induced land clearing, bushfires, hunting and disease,” he added.
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