Long before the koala became a conservation icon, museum drawers quietly stored its forgotten genetic past. Now, by decoding DNA from centuries-old pelts and bones, scientists have uncovered a hidden chapter in koala history – revealing extinct lineages, deep scars from climate and the fur trade and new hope for smarter conservation. What we lost in the past may guide how we protect what is left.
The cuddly looking koala faces a storm of threats – from climate change and habitat loss to fatal sexually transmitted infections. Australia’s beloved “bear” just cannot seem to catch a break.
But in a surprising twist, its past may hold the key to its future.
“Understanding koalas’ genetic diversity can help us to predict how resilient they will be to each of these threats,” explains co-author Binia De Cahsan Westbury, a molecular evolutionary biologist at the University of Copenhagen in Denmark.
Researchers raided museum archives around the world to find genetic samples from koalas collected by specimen hunters over the past two centuries. Comparing these with genetic samples from modern-day koalas enabled them to identify three distinct ancestries for koalas today – along with a ghost lineage that has been lost to time.
“Including these historical koalas gives us an idea of the baseline before these threats occurred,” says De Cahsan Westbury. That begs another question: “Can we aim to reach that again with conservation efforts?”
DNA clues hidden in dusty museum drawers
Long before modern genetics, museums relied on specimen collectors – a cross between bounty hunters and naturalists – who scoured the globe for exotic animals. The 1800s and early 1900s were their heyday, and thanks to them, museum drawers now overflow with koala pelts.
As a result, natural history museums in Europe and North America “have literally bucketloads of koala pelts around,” says co-author David Duchêne, who studies genetics and genomics in biodiversity at the University of Copenhagen.
Unfortunately, some specimen collectors were not big on the details of where or when a pelt was collected. “Some of them have handwritten labels that either cannot be read anymore or that just say ‘Australia’,” De Cahsan Westbury notes. “It is a shame – you have to exclude those from the analysis.”
The researchers painstakingly tracked down 37 specimens with clear origin stories from museums in Australia, Germany, England, the United States, Scotland, Sweden and Norway. They used samples of skin, hair or bone powder to collect genetic material from these historical koalas, which were taken from the wild between 1817 and 1980. Next, they compared these koala forebearers with genetic material from 25 modern koalas collected between 1995 and 2017.
Climate and fur trade left deep genetic scars
By looking for the genetic signature of past inbreeding in the koala genome, researchers found evidence of two plunges in the breeding population over the course of the species’ recent evolutionary history, they say – one about 30,000–50,000 years ago and another about 200 years ago.
The first crash came tens of thousands of years ago, when a cooling climate reshaped Australia and eucalyptus – the koala’s only food – grew scarce. “That led to long-term, slow, steady population decline,” explains De Cahsan Westbury, “as groups became isolated from each other.”
Millennia later, a very different threat caused the second crash: fashion. In the late 1800s and early 1900s, koala fur became a must-have luxury item in Europe and North America. Koala fur was all the rage in the United States, Europe and Canada from the 1880s to the 1920s. “Marsupials have incredibly soft fur,” Duchêne says, which made high-grade koala pelts ideal for lining women’s coats and gloves. But koala fur was also valued for its warmth and water resistance, and lower-quality pelts were used for outdoor equipment, including sleeping bags.
Researchers estimate that 8 million koalas were hunted for their pelts over the decades, with 800,000 killed in a single month when Queensland officials declared open season on koalas in August 1927.
By the time the koala trade was outlawed, koalas had been “hunted to near extinction in southern Australia,” De Cahsan Westbury says, with devastating loss of life across the continent.
Analysing the genetic samples revealed three distinct lineages of koalas alive today – a northern lineage in northern New South Wales; a central lineage in southern New South Wales; and a southern lineage in Victoria.
But the historical specimens revealed something unexpected: a fourth lineage, now lost to time – a genetically distinct population of koalas once found in Queensland, more closely related to the central lineage than their northern neighbours.
That suggests “maybe there were some migration corridors connecting different populations or barriers between this one and others in the north – we would not have found out if we did not have the historical samples,” De Cahsan Westbury explains.
How genetic maps may help to save koalas
Because of habitat fragmentation, researchers worry that the many isolated pockets of koalas risk inbreeding. But bringing in totally unrelated koalas to shore up this specific population risks wiping out valuable genetic diversity on the species level.
Understanding which populations of koalas share a common ancestry presents an opportunity for conservation ecologists to give koalas a genetic boost, De Cahsan Westbury says.
Even if hundreds of miles of farmland and human infrastructure separate two populations of koalas today, if they are from the same lineage, they were once part of the same breeding pool.
“If we know that these populations were naturally connected in the past, keeping them isolated does not make sense,” De Cahsan Westbury says. This means that conservationists could safely introduce members of one population to another population without lowering the species’ overall genetic diversity.
Translocating koalas has a long and dubious history in Australia. In the late 1800s, an organisation called the Acclimatisation Society of Victoria – which was primarily occupied with establishing European animal and plant species in Australia out of a sense of nostalgia, De Cahsan Westbury explains – transported koalas from the mainland to the islands and back again for aesthetic reasons.
“They did not know about genetics – they would just constantly move animals around, not thinking about the consequences,” she says. “Was it good? Was it bad? It is a bit hard to say for the koalas.”
With the knowledge available today, setting a koala loose in an unfamiliar eucalyptus stand would require mountains of preparatory work. Any transported koala bachelors or bachelorettes would have to be thoroughly vetted to avoid introducing disease or harmful genetic mutations into their new population, the researchers emphasise.
All that time at the laboratory bench mapping the koala’s family tree will be worth it if it can “increase the koalas’ genetic diversity and their ability to survive in the future,” De Cahsan Westbury concludes.
And it might not end there – similar work could help to rewrite the genetic history of other endangered species still hiding in museum drawers.
