The Pak are a species of highly xenophobic humanoids originating from a system near the Galactic Core in the Ringworld Universe.
Humans are descended from a colony of Pak Breeders that were stranded on Earth 2.5 million years ago. The Protectors that built the colony ship died when their Tree-of-Life crops failed. The original Pak Breeder form (Homo habilis) evolved into modern humanity (Homo sapiens). Other Earth primates (such as gorillas, chimpanzees, and orangutans) are also descended from the original colony of Pak Breeders.
Pak Protectors are fully sentient, and are far more physically strong and intellectually intelligent than ordinary humans, possessing "diamond like" clarity of thought. However, this superior intelligence only serves a Pak Protector's hard-wired instincts to protect its bloodline at any costs, including resorting to war, mass murder, or genocide. Pak Protectors reportedly constructed the Ringworld.
In 2433 it was discovered that the Morlocks of Wunderland were also the descendants of an ancient Protector expedition, similar to the one that planted the seed of humanity on Earth.