The four cuts at the top of this skull "are clear chops to the forehead," says Smithsonian forensic anthropologist Douglas Owsley. Based on forensic evidence, researchers think the blows were made after the person died. Donald E. Hurlbert/Smithsonian hide caption

itoggle caption Donald E. Hurlbert/Smithsonian

Bates experienced migraines as a child. She made this painting to depict how they felt to her. Courtesy of Emily Bates hide caption

itoggle caption Courtesy of Emily Bates

Doctors at a hospital in Aleppo, Syria, treat a boy injured in what the government said was a chemical weapons attack on March 19. Syria's government and rebels accused each other of firing a rocket loaded with chemical agents outside of Aleppo. George Ourfalian/Reuters/Landov hide caption

itoggle caption George Ourfalian/Reuters/Landov

The research of British naturalist Alfred Russel Wallace (1823-1913) played a pivotal role in developing the theory of natural selection. But over time, Charles Darwin became almost universally thought of as the father of evolution. Hulton-Deutsch Collection/Corbis hide caption

itoggle caption Hulton-Deutsch Collection/Corbis

A mammoth spinning vortex is seen on Saturn, in this "false-color" photograph released by NASA Monday. The image was captured by the Cassini spacecraft. A related image, presenting what a human eye would see, is farther down this page. NASA hide caption

itoggle caption NASA

Beekeepers demonstrate at the EU headquarters in Brussels Monday, as lawmakers vote on whether to ban pesticides blamed for killing bees. Georges Gobet/AFP/Getty Images hide caption

itoggle caption Georges Gobet/AFP/Getty Images