Azernews.Az

by Alimat Aliyeva

A new genomic study has revealed that koala populations experienced a dramatic decline tens of thousands of years before humans arrived in Australia, challenging long-held assumptions about the species’ history, AzerNEWS reports, citing foreign media.

According to researchers from the University of Sydney and Texas A&M University, environmental changes—not human activity—were the primary cause of the population collapse.

The study suggests that all modern koalas descend from a single ancestral population that managed to survive a series of severe climate shifts, including glacial periods and prolonged cold, dry conditions. As Australia gradually became more arid, koala habitats shrank and fragmented, isolating populations across the continent.

Researchers found that many western koala populations eventually disappeared, while a small group in eastern Australia survived through some of the harshest climatic conditions. Over time, this resilient population became the ancestor of all koalas living today.

“The study rewrites the timeline of the koala’s genetic history in Australia,” said Toby Kovacs, a PhD candidate at the University of Sydney and lead author of the research.

By analyzing genetic mutations in modern koalas and tracing them backward through time, scientists reconstructed the species’ demographic history over the past 100,000 years. Using genome sequencing from parent-offspring groups and examining 457 koala genomes, the team identified a major population bottleneck approximately 60,000 years ago, likely caused by habitat loss during a period of intense glacial cooling and drought.

The findings, published in Molecular Biology and Evolution, could have important implications for conservation efforts. Modern koalas continue to face numerous threats, including habitat destruction, bushfires, disease, and climate change. Since 2022, koalas have been listed as endangered in several parts of eastern Australia.

An interesting detail is that koalas possess one of the most specialized diets in the animal kingdom, feeding almost exclusively on eucalyptus leaves. Because these leaves provide relatively little energy, koalas sleep between 18 and 22 hours a day to conserve energy. This unique adaptation has helped them survive for millions of years, but it also makes them particularly vulnerable to environmental changes that affect their food supply.