Greg O'Brien gathers his thoughts before a run in 2013. "Running is essential," he says. Michael Strong/Living With Alzheimers hide caption

itoggle caption Michael Strong/Living With Alzheimers

Students Patrick Rohrer, Sarah Warthen, Alix Piven and Lauren Urane are led by Mercyhurst University Archeologist Andy Hemmings. Their project has picked up where Florida's State Geologist Elias Sellards left off in 1915. Sellards led an excavation of the site where workers digging a drainage canal found fossilized human remains. Greg Allen/NPR hide caption

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Fernandina's Flicker (Colaptes fernandinae), a woodpecker found only in Cuba. Pete Oxford/Minden Pictures/Corbis hide caption

itoggle caption Pete Oxford/Minden Pictures/Corbis

A field of unharvested wheat is seen in Ashby-de-la-Zouch, England, in 2012. Wheat wasn't cultivated in Britain until some 6,000 years ago, but DNA evidence suggests early Britons were eating the grain at least 8,000 years ago. Darren Staples/Reuters/Landov hide caption

itoggle caption Darren Staples/Reuters/Landov

Tim Meyers on his four-acre vegetable farm in southwestern Alaska. Behind him: an endless sea of tundra, and a glimpse of the town of Bethel. Eugenie Frerichs for NPR hide caption

itoggle caption Eugenie Frerichs for NPR

An image of Ceres taken by NASA's Dawn spacecraft shows that the brightest spot on the dwarf planet has a dimmer companion. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA hide caption

itoggle caption NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

An overgrowth of Clostridium difficile bacteria can inflame the colon with a life-threatening infection. Dr. David Phillips/Getty Images/Visuals Unlimited hide caption

itoggle caption Dr. David Phillips/Getty Images/Visuals Unlimited