Roddy McDowall was 42 in Conquest of the Planet of the Apes when he played the character 'Caesar'.
That was over 52 years ago in 1972.
In 1998 he died aged 70, starring in 166 films in his career, 102 of those after Conquest of the Planet of the Apes was first released. If he were alive today he would be 95.
In Conquest of the Planet of the Apes, I think Roddy McDowall looks: