The NY Times has a story about the last Mammoths on a small island in the Bering Sea.  Using a variety of data, researchers, led by a team from Penn State University, have shown that the Woolly Mammoths on St. Paul Island went extinct about 5,600 years ago.  The cause seems to be due to a lack of fresh water.

The study, led by scientists from Pennsylvania State University along with scientists from elsewhere in the United States and Canada, analyzed a variety of indicators to show that these woolly mammoths became extinct about 5,600 years ago. According to Russell W. Graham, a professor of geosciences at Pennsylvania State and the study’s lead author, this may be the most precisely dated prehistoric extinction.

The authors of the study found that rising seas, which shrank the island’s size, were not enough to cause extinction, but may have indirectly caused the extinction event: The swelling seas reduced available habitat and freshwater sources, making life difficult for the giant animals.

The scientists analyzed four proxies for megafaunal presence (in this case, mammoths): sedimentary ancient DNA and three fungal spore types from near a lake, a key source of freshwater on the island. They also were able to get a sense of the vegetation on the island at the time, using several proxies from sediment cores. These cores showed that the area around the lake was likely stripped of vegetation by the mammoths, which might have sped up the lake’s erosion, causing it to fill in and worsening its quality.

The original research paper appeared in PNAS.