A Navajo family in front of a hogan, a traditional Navajo home, in Canyon de Chelly in 1927. Northern Arizona University Cline Library hide caption

itoggle caption Northern Arizona University Cline Library

Scientists recently mapped the louse genome. It has only 108 million letters of DNA, which is fewer than in other insects they've mapped. Courtesy Aurelie Veracx hide caption

itoggle caption Courtesy Aurelie Veracx

A cleanup worker vacuums oil near sullied marsh grass in Barataria Bay on the coast of Louisiana. Patrick Semansky/AP hide caption

itoggle caption Patrick Semansky/AP