Hunted to extinction

Hunted to extinction
Ancient rump roasts?



By Ben Harder


Scientists have long been curious about the massive die-off of the world's large animals-mastodons, giant kangaroos, and lionlike marsupials among others-and they've debated whether their disappearance was caused by climate change, infection, or something else. Now evidence from two continents points a guilty finger at ancient hunters. Fossils from Australia show that after humans arrived about 56,000 years ago, almost all animals larger than 100 pounds vanished. A similar extinction took place in North America when humans arrived some 40,000 years later.





Bones and eggshells unearthed in Australia provide the most reliable date yet-about 46,000 years ago-for a mass extinction of the continent's largest marsupials, reptiles, and birds. That timing makes sense, explains Tim Flannery, coauthor of the study, because hunter-gatherers could have pursued their prey to extinction or disrupted crucial habitats as they dispersed across the southern landmass. A second study, based on a computer model of the human diaspora in North America, demonstrates how overzealous hunters could have exterminated 30 large species, including the mastodon and the woolly mammoth, between 10,000 and 14,000 years ago.


The new studies, both published last week in the journal Science, deliver a blow to a competing theory that natural climate change was the culprit. A long dry spell in Australia that is crucial to the theory now appears to have come 20,000 years too late. But Ross MacPhee, a curator of zoology at the American Museum of Natural History in New York, isn't ready to rule out another rival explanation that migrating humans introduced diseases lethal to animals. The slaughter theory requires evidence of many butchery sites, and that will require more digging.