Fossils link extinction to humans
Three Australian caves have yielded a treasure trove of fossils of ancient kangaroos, marsupial lions and giant lizards that roamed the outback for hundreds of thousands of years.
These so-called megafauna went extinct about 45,000 years ago, shortly after humans arrived on the continent.
Researchers, writing in Thursday’s issue of the journal Nature, suggest that the extinction was the result of the human use of fire for hunting -- and not climate change, as some scientists have suggested.
The caves, on the Nullarbor Plain in south-central Australia, contained 69 species of mammals, reptiles and birds, including a 20-foot-long lizard, eight new types of kangaroos and the first complete skeleton of a 175-pound carnivore known as a marsupial lion, the researchers reported.
“These animals lived through a whole range of climates,” said co-author John Long, head of sciences at the Museum Victoria in Melbourne.
The beasts in the caves died 200,000 to 800,000 years ago, most likely after falling through the vertical cave entrances.
The animals were mostly herbivores and could have thrived only on a rich variety of trees and plants.
“There was a diverse vegetation that doesn’t exist today,” said Gifford Miller, a geologist at the University of Colorado who was not involved in the research but has long worked in Australia.
The human immigrants of the time hunted by burning broad swaths of landscape to drive animals into the open, where they could be speared.
The destruction of their habitat -- and hence the food chain -- is believed to have taken a much greater toll on the animals than the actual killing.
Still, Jim Mead, a paleontologist at Northern Arizona University who was not involved in the study, said subtle climatic changes could not be ruled out as a contributing factor in the extinction.
“There is no question that humans played a role,” he said. “The question is how much of a role.”