Australia's megafauna dies out

Between about 50,000 and 40,000 years ago, Australia lost almost all of its large animals. Gone were the giant wombat relative Diprotodon, the marsupial lion Thylacoleo, the short-faced kangaroo Procoptodon, the giant flightless bird Genyornis and the huge monitor lizard Varanus priscus. Most land animals over about 44 kilograms disappeared, leaving the red kangaroo as the largest marsupial. The timing matters: people reached Australia about 50,000 years ago, and the losses came soon after.¹⁴

Dating is the key. A 2001 study led by Richard Roberts dated Genyornis eggshell and found that it vanished across the continent around 46,000 years ago. A 2012 study by Susan Rule and colleagues, of a lake sediment core at Lynch's Crater in Queensland, found that dung fungus spores, a proxy for large herbivores, fell about 41,000 years ago, before vegetation and charcoal changed, which argued against climate as the first cause. A 2016 study by Frederik Saltre and colleagues modelled hundreds of dated fossils and concluded that the extinctions came in the narrow window after human arrival, not tied to climate.¹²³

Others point to climate, since Australia was drying and its water supplies faltering over this period, and to the difficulty of dating the youngest fossils, since few finds are younger than 45,000 years. Humans, fire and climate may have combined. The event reshaped Australian vegetation, and it is the earliest and best-dated case in the debate over the Pleistocene extinctions.⁵³