This retro book cover is for Inherit the Earth by Claude Nunes.
This book features cover art by Ted Hanke, making it one of the handful of covers Hanke illustrated. He also did art for Mike Mars, Astronaut and Mike Mars and the Mystery Satellite — both of which were written by Donald A. Wollheim and released in 1966. Hanke also created the cover for Mysteries, Monsters and Untold Secrets by George Laycock.
Of course, because Hanke has limited credits, it’s possible that he was very prolific, yet much of his work went uncredited.
Inherit the Earth is part of the Ace “Doubles” collection, which features two novels bound back-to-back. The novel on the other side of this book is Dawnman Planet by Mack Reynolds.