If so, could someone please cite examples to get me back on track. The Protectors that built the colony ship died when their Tree-of-Life crops failed. Humans are descended from a colony of Pak Breeders that were stranded on Earth 2.5 million years ago. Sometimes I read so fast that I miss things. The Pak are a species of highly xenophobic humanoids originating from a system near the Galactic Core in the Ringworld Universe. With the advent of the hyperspace shunt, someone should have visited Home. How come I have never seen reference to Home being wiped out by plague (that would be a likely story for the protectors to send to Earth) or reference to protectors on Home (I have not read 'Ringworld Engineers' yet and I understand that protectors have something to do with Ringworld). Many years later ('Known Space' time) I believe We Made It buys the hyperspace shunt from the Outsiders. Destroyer of Worlds depicts a confrontation between the Pak and the Puppeteers. The Pak also appear in several of Niven's later novels, notably those set in the Ringworld. The net result is that you have a planet full of childless protectors. The Pak first appeared in 'The Adults', which appeared in Galaxy in 1967 this story was expanded into the novel Protector by Larry Niven (1973). After they arrive there, the virus spreads to all members of Home. Brennan infects Truesdale with the modified Tree-of-Life virus just before they get there.

Ringworld pak protector