Ron Harper, who co-stars as astronaut Alan Virdon in 20th Century-Fox Television’s “Planet of the Apes” series for CBS-TV, was born January 12 in Turtle Creek, Pennsylvania. His parents, George and Mabel Harper, still reside there. Mr. Harper is a retired steel foundryman.   After graduation from Princeton University, young Harper turned down a fellowship to the Harvard Law School in favor of becoming an actor. He performed two seasons with the Princeton University Players and then went to New York to study with the noted dramatic coach, Lee Strasberg.   After appearing in such television shows as “Studio One” and “The Armstrong Theatre,” Harper served an enlistment in the U.S. Navy.   Following his separation from the service, Harper appeared on Broadway in “Night Circus” and “Sweet Bird of Youth.” and also toured the country in the latter production.   Beyond guest-starring in many television shows, Harper has starred as a regular on the “87th Precinct,” “Wendy and Me” and “Garrison’s Gorillas” series.   Harper and actress Sally Stark, a regular on the “Love of Life” daytime series, were married June 1, 1974. They maintain an apartment in Manhattan.   In “Planet of the Apes,” Harper and fellow astronaut Pete Burke (JAMES NAUGHTON), become lost in space following a malfunction of their rocket. When they return to earth, they discover they have passed through a “time warp” which advances them 2000 years in time when the apes rule the planet.   Harper is an excellent oil painter and his diversions include tennis, sailing and horseback riding.   * * * * Birthplace  Turtle Creek, Pa.     Birthdate  Jan. 12   Height  6' 1"     Weight  185 lbs.   Hair  Blond     Eyes  Blue-Green   #   June, 1974