A worker welds parts in fans for industrial ventilation systems at the Robinson Fans Inc. plant in Harmony, Pa., in February. Hourly wages in the U.S. remained unchanged last month. Keith Srakocic/AP hide caption

itoggle caption Keith Srakocic/AP

Raymond Smith of Charleston, S.C., kneels in prayer in front of the Emanuel AME Church in Charleston before a worship service on June 21. Stephen B. Morton/AP hide caption

itoggle caption Stephen B. Morton/AP

Mammoths had a distinctive version of a gene known to play a role in sensing outside temperature, moderating the biology of fat, and regulating hair growth. That bit of DNA likely helped mammoths thrive in cold weather, scientists say. Courtesy of Giant Screen Films, 2012 D3D Ice Age, LLC/Penn State University hide caption

itoggle caption Courtesy of Giant Screen Films, 2012 D3D Ice Age, LLC/Penn State University