An alternate Earth has two species coexisting in it: Humans and Khnosh (/x'ʔɒʃ/) since the Stone Age. Adult Khnosh have the intelligence of the average 8 year old human but the strength of a human adult. Humans and Khnosh cannot interbreed with each other. Khnosh have the body shape of humans, but have blue skin and orange eyes that make them visually distinct from each other. The ratio of Humans to Khnosh is 4:1.
Khnosh are capable of performing simple, repetitive tasks such as screwing caps on bottles, assembling furniture, cooking food in restaurants, lifting and organizing boxes, and farming (without the use of complicated machines). They can live on their own and perform most tasks needed for independent living (making beds, cooking, brushing teeth, etc.) but most Khnosh cannot perform certain functions in life (ex. paying taxes).
Humans first encountered Khnosh in Anatolia (Western Turkey) when both species were living as hunter-gatherers. From Anatolia, they soon spread throughout Europe, followed by the Eastern Hemisphere, and were introduced into the Americas by European colonists. This means that Native Americans did not have Khnosh in the pre-Columbian era.
So what would a society where humans coexist with a second species with the intelligence of an 8 year old look like?