海角大神

Seventy-five percent of Americans that global warming is a 鈥渧ery鈥� or 鈥渟omewhat鈥� serious problem, even if they continue to debate whether human activity is to . But it turns out that other species may face an even greater threat than climate change: humans themselves.

In 2004, professional research diver Brian Kakuk聽managed to inspect a Bahaman sinkhole whose layer of toxic water had put off other explorers 鈥撀燽ut had perfectly preserved fossils of species now extinct on Great Abaco Island. Mr. Kakuk and his colleagues published their聽聽Monday聽in the journal Proceedings of the National Academy of Sciences.

The fossils, which included complete skeletons of crocodiles and tortoises, 鈥済ave us an unparalleled snapshot of what the Ice Age life would have been like on a Caribbean isle,鈥� the study鈥檚 lead author, David Steadman, .

In a word, it was tough. Dramatic climate changes during the Pleistocene-Holocene transition, roughly 10,000 years ago, condensed the island to just one-tenth of its former size as glaciers melted, seas rose, and the local flora turned tropical. All around the globe, the end of the ice age set off a vast sweep of extinction: that鈥檚 when legendary species like wooly mammoths and giant sloths .

For years, scientists have debated whether that bout of global warming is responsible for the extinctions, or whether mankind also helped, as climate change let us venture out to new territory: crossing the Bering Strait to the Americas, for instance.

But people have only lived in the Bahamas for the last 1,000 years, giving 聽an opportunity to compare the sinkhole鈥檚 oldest fossils, deposited before the big melt, with post-Ice Age bones, and those of animals that died after humans came to the island.

Scientists hoped that seeing which species made it from one era to the next, then the next 鈥撀燼nd why they lived or died out 鈥撀爓ould hold clues about how animals adapted to the changing climate, and then to humans, who altered the environment even more by hunting and clearing land for agriculture.

Of the 95 species studied, 39 are now extinct. Some聽44 percent of the extinctions resulted from changes in climate and rising seas: perhaps because smaller populations forced inbreeding, Dr. Steadman suggests. But the majority adapted and were getting along just fine, until humans changed the game: the remaining 56 percent were wiped out in the last 1000 years.

A $375,000 National Science Foundation grant will now help the team determine whether genetic differences played a role helping some animals adjust to homo sapiens better than others.

It鈥檚 possible that the answer will help preserve biodiversity, as animals today again face the twin challenges of global warming and human activity, what University of Florida master鈥檚 student and co-author Hayley Singleton calls 鈥渢he perfect storm.鈥澛�

鈥淚f we鈥檙e losing that high of a percentage over a millennium, is anything going to be left by the time we get to the next ice age?鈥� .