US President Barack Obama and Cuba’s Raul Castro shook hands and sat near each other Friday at a historic Summit of the Americas, a new milestone in efforts to end decades of animosity. Obama and Castro, separated by the presidents of Ecuador and El Salvador, stood before taking their seats in the second of three rows at a Panama City convention center as the country’s national anthem was sung. The sight of Obama and Castro in the same room instantly became a potent symbol of their bid to renew diplomatic ties that were severed in 1961. It was the first time that a Cuban leader attended the summit in its 21-year history.