Caesar was born in the San Francisco biotech company Gen-Sys Laboratories as the son of a female chimpanzee nicknamed Bright Eyes and an alpha male chimpanzee of Bright Eyes' troop in the West African Jungle. Following the death of his mother, Caesar was found by the chimpanzee handler, Robert Franklin, and the eccentric scientist, Will Rodman. Upon the discovery, they realized that Bright Eyes' earlier rampage was not due to the ALZ-112 (an experimental drug that, through neurogenesis, repairs brain cells and increases mental capabilities) in her system, but due to her maternal instincts to protect her newborn baby whom she had secretly given birth to a day or two earlier. Because Bright Eyes' aggression was believed to be the effects of the ALZ-112, head of Gen-Sys, Steven Jacobs, shut down the project and ordered the apes in the facility's possession, to be euthanized. However, Franklin was unable to bring himself to put the infant down and convinced a reluctant Will to take him instead, sparing the infant's life in the process
Taking him home, Will discovered, to his delight, that the infant chimpanzee had inherited the ALZ-112 from his mother after he and his father, Charles Rodman, who suffers from Alzheimer's disease (which Will was working on in Gen-Sys, desperately searching, in vain, for a cure for his father) witness the infant drinking from a bottle on his own at only two days old. Three years later, Will decided to keep the infant whom he named Caesar, and raised him as his own while continuing his life's work on the ALZ-112 in secret. At eighteen months, Caesar was signing up to twenty-four words. At age two, he completed puzzles and models designed for human children eight years and up. At age three, he completes the Lucas Tower with a perfect score of fifteen moves and became an expert chess player as well. Throughout his early years, Caesar continued to show signs of heightened intelligence and cognitive skills that far exceeded that of a human counterpart, much to Will's amazement
One day, Caesar saw children outside of his attic window playing on bikes and, after seeing the children leaving their bikes in a garage, snuck out a window while Will was distracted assessing his father's improvement after supposedly curing him with the ALZ-112. However, Alice Hunsiker discovered Caesar playing with a bike in the garage and alerted her father, Will's short-tempered neighbor, Douglas Hunsiker, who threatened Caesar with a baseball bat until Will and Charles, after discovering his absence, arrived to defend him
