The Neanderthal Man (1953)

Starring Robert Shayne, Joyce Terry, Richard Crane, Doris Merrick, Beverly Garland
Directed by E.A. Dupont
(actor & director credits courtesy IMDB.com)

A scientist discovers a formula that returns cats to their prehistoric forms, and then experiments on himself, eager to prove his theory that neanderthal man was more intelligent than given credit for.

This isn't a great movie, with many ludicrous scenes and a number of plot holes in the screenplay, but I enjoyed it immensely, and it affords familiar 1950s character actor Robert Shayne with one of his few starring roles.  As the cantankerous Clifford Groves, Shayne spits out a plethora of sharply-worded and impressively composed insults to the colleagues that reject his theories, and anyone getting too close to discovering his secret experiments.  The rest of the story isn't quite as creatively written, but I had a great time watching it, especially the filmmakers' attempts to pass off a tiger as its saber-toothed ancestor by trying to integrate footage of the creature with a laughable stuffed replica.  One of a series of 1950s science fiction pictures by the writing team of Aubrey Wisberg and Jack Pollexfen, the film is far from the serious drama they may have intended, but the actors give it their all, although Joyce Terry is a bit too earnest, looking to emote everytime the camera is on her.  Beverly Garland, who of course went on to a decades-long career in film and television, appears in an early part as a local waitress menaced by the neanderthal man.