This episode's headline: Defending Claims; Gay Marriages; Ancient Planet; Flashpoints; Shields and Brooks. ANCHOR: JIM LEHRER; GUESTS: WALTER PINCUS; MARK SHIELDS; DAVID BROOKS; ALAN BOSS; CORRESPONDENTS: KWAME HOLMAN; RAY SUAREZ; SPENCER MICHELS; MARGARET WARNER; GWEN IFILL; TERENCE SMITH; KWAME HOLMAN