SACRAMENTO, CALIFORNIA—According to a Live Science report, David Zeanah of California State University, Sacramento, representatives of the Thalanyji people, and their colleagues have analyzed more than 4,400 cutting and grinding tools recovered from open-air sites on Barrow Island, which is located off the coast of northwestern Australia. Between 29,000 and 19,000 years ago, when sea levels were lower, the island would have been a high plateau connected to what is now Australia by a coastal plain. Zeanah said that most of the tools found in caves on Barrow Island were made from limestone, which was readily available in the area. The tools recovered from open-air sites, however, were made mostly of rocks that match sources on what is now mainland Australia. “The open sites provide clear links to the mainland geologies, and that infers that people were using the coastal plain that’s underwater now,” Zeanah said. As for the number of limestone tools recovered in caves, Zeanah thinks that limestone tools left at open-air sites may not have survived the millennia of exposure to the elements. Then, as sea levels rose and Barrow Island was separated from the mainland, people who settled in the caves would have had to rely on the local limestone to make tools, he explained. Read the original scholarly article about this research in Quaternary Science Reviews. To read about stone tools found at an Aboriginal site that is now underwater in the Dampier Archipelago, go to "Around the World: Australia."