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Did Fires Cause Large Extinctions?
By measuring radioactive carbon isotopes in fossilized eggshells, researchers found more evidence that man's extensive use of fire, which resulted in a dramatic change in the ecosystem, accounted for the massive animal extinctions in Australia some 50,000 years ago. The reconstructed, 140,000-year dietary record for two flightless birds showed they switched from nutritional grasses to desert scrub for forage, which coincided with the arrival of humans to the continent and not with a climate change.
Consequently, animals like the emu that were more tolerant of dietary changes survived, while more-specialized feeders perished. The massive demise resulted in the extinction of 85 percent of Australia's largest mammals, reptiles and birds--creatures that included 19 types of marsupials or kangaroo-like animals, a 25-foot-long snake, a 25-foot-long lizard and a tortoise the size of a small car.
This image accompanied NSF press release, "When Down Under Went Up in Smoke."
Credit: Nicolle Rager Fuller, National Science Foundation
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