A 1972 Hammer film starring (you guessed it) Christopher Lee and Peter Cushing. From Wikipedia:
Prof. Emmanuel Hildern (Peter Cushing), a Victorian era scientist is shown in what appears to be a laboratory meeting a young doctor. Hildern excitedly tells the doctor that he needs help because he has discovered a form of evil that is real, a living being, and that he has unwittingly unleashed the evil thousands of years too soon. Hildern then recounts how his discovery was made.
In a flashback, Hildern recounts his return in 1894 from an expedition to New Guinea where he has discovered an abnormally large humanoid skeleton. Paradoxically, the skeleton is far older than previously recovered specimens, but also much more advanced. Hildern hopes the discovery will earn him the prestigious Richter Prize. Hildern has little time to rejoice before receiving word that his wife, institutionalized for years, has finally died. This he learns from his brother James Hildern (Christopher Lee) who runs the asylum where Hildern’s wife had been held in secret. While visiting the asylum, James tells his brother that he made a psychiatric study of Hildern’s wife and plans to publish the findings in the hope of winning the Richter Prize. He also tells Hildern that he will no longer subsidize Hildern’s expeditions.There's more, but it's best if you just watch the movie.