Overview
- The study, published June 9, 2026, directly measured the koala germline mutation rate by sequencing four parent–offspring trios and found it to be roughly half the human rate.
- Applying that species-specific clock to 457 modern koala genomes, researchers reconstructed a population decline starting about 100,000 years ago with a critical bottleneck by roughly 60,000 years ago.
- The timing of the crash matches Late Pleistocene environmental shifts, including glacial drying and the expansion of the Nullarbor Plain, which reduced and fragmented suitable koala habitat.
- After the glaciers retreated, survivors expanded and split into five genetically distinct eastern populations between about 16,500 and 6,000 years ago.
- Authors say the revised timeline removes initial human arrival as the primary cause of the ancient decline but warns that modern losses from land clearing, bushfires, disease and hunting are now eroding koala populations and genetic diversity and should guide conservation action.