The Ape Mastermind was the predecessor of more famous malevolent monkeys, Super Gorilla Grodd and Ultra-Humanite Ape, although his legend didn't last as long as his legacy. A mutant simian living in central Africa, he enlisted the aid of unwitting human agents while instilling within the primitive minds of his ape allies of various types the ability to create fire. So decades before Ultra recruited humans to his Secret Society of Super-Villains and Grodd tried to do likewise after his attempted conquests of Gorilla City had failed, it was this behemoth who blazed the trail in the golden age. Still, this master plan was not sufficient to defeat the World's Mightiest Mortal, who was more than a match for the World's Smartest Chimp. Whether after his defeat, Ape Mastermind returned and perhaps displayed mental abilities like his counterparts is unknown. Another annoying animal who plagued Captain Marvel and his allies using a similar magnificent yet malevolent mind while employing various bodies was that of the alien worm known as Mister Mind.
Grodd had been imprisoned in Gorilla City following a clash with the Flash of Earth-One as a faux human known as Drew Drowden. In order to escape, Grodd ingested a pill which transplanted his mind into the body of criminal William Dawson, displacing that man's psyche. Grodd as Dawson carried out a series of battles with his arch-enemy the Flash, still possessing his force of mind power. As for Dawson, his mental force spawned by Grodd's power created the supervillain known as Psykon, who returns to battle his simian adversary. After tricking Grodd with Flash's help, Dawson regained his own body while the gorilla's mind merged with a derelict. But Grodd would return!
On Earth-Two, the simian Ultra-Humanite was preceded decades before by another mental manipulator in Tricky O'Rickey, a crook who stole the mind enhancing thinking cap devised by Professor Hartwell Jackson. After using it in battle versus the Flash, Tricky relinquished the cap following his defeat. Although Jackson confirmed upon receiving it back from the Flash that he would destroy it, the cap ended up in the hands of the Thinker who used it repeatedly against Flash.