Here's why:
* Eye color is determined by melanin: The amount and distribution of melanin, a pigment, in the iris determine eye color. Blue eyes have less melanin than brown eyes.
* Genetic mutation in humans: Blue eyes in humans arose from a genetic mutation that occurred around 6,000 to 10,000 years ago. This mutation reduced the amount of melanin in the iris, making it appear blue.
* No similar mutation in other primates: This specific genetic mutation hasn't been found in other primate species.
While some primates may have eyes that appear bluish in certain lighting conditions, their eyes are not actually blue.