An Israeli Merkava tank near the Hamas-controlled Gaza Strip border in southern Israel, on Thursday. The Pentagon confirms that Israel tapped a U.S. weapons stockpile for tank rounds. Debbie Hill/UPI/Landov hide caption

itoggle caption Debbie Hill/UPI/Landov

Eduard Egarter-Vigl (left) and Albert Zink (right) sample Italy's mummified iceman for genetic analysis in November 2010. Previous research suggests he, too, was predisposed to heart disease. Samadelli Marco/EURAC hide caption

itoggle caption Samadelli Marco/EURAC

Palestinian children fill plastic bottles and water containers with drinking water from a public tap in Jabalia in the northern Gaza Strip on July 27. Ashraf Amra/APA/Landov hide caption

itoggle caption Ashraf Amra/APA/Landov

An Israeli army officer walks near the entrance of a tunnel allegedly used by Palestinian militants for cross-border attacks, at the Israel-Gaza border. A network of tunnels Palestinian militants have dug from Gaza to Israel is taking center stage in the latest war between Hamas and Israel. Jack Guez/AP hide caption

itoggle caption Jack Guez/AP

With displaced Palestinians still inside, a youth walks by the debris in a classroom at the Abu Hussein U.N. school in Jebaliya refugee camp, northern Gaza Strip, hit by an Israeli strike earlier Wednesday. Tank shells hit the school, where hundreds of Palestinians had taken refuge. Lefteris Pitarakis/AP hide caption

itoggle caption Lefteris Pitarakis/AP