Final answer:
The megafauna in Australia went extinct about 40,000 to 50,000 years ago, shortly after the arrival of humans. Human hunting is considered a key factor in these extinctions.
Step-by-step explanation:
The extinction of Australian megafauna began around 40,000 to 50,000 years ago. This period coincides with the arrival of humans in Australia, not long after which large species such as the marsupial lion, a giant wombat, and several giant kangaroo species disappeared. The evidence suggests that, although climate may have played some role, human factors, particularly hunting, largely precipitated these extinctions. This pattern is not unique to Australia as similar megafaunal extinctions occurred in other regions like North America 10,000 - 12,000 years ago, and on Madagascar about 2,000 years ago, alongside human colonization.