Koalas nearly vanished before humans reached Australia, DNA suggests

A major genetic study has found that koalas almost became extinct about 100,000 years ago because of major climate changes, long before the first humans reached Australia.By studying the DNA of hundreds of koalas, an international team of researchers found that every koala alive today came from a very small group of survivors that lived through severe ice ages. The findings, published in the journal Molecular Biology and Evolution by Oxford University Press, change the accepted timeline of the species and show that its earliest major population crisis was caused by natural climate change, not human activity.A team led by the University of Sydney and Texas A&M University studied 457 koala genomes to trace how the marsupial population declined and recovered over thousands of years.To improve accuracy, the scientists measured the koala mutation rate for the first time by examining genetic changes across four parent-offspring trios.