I was thinking of a situation, in which there are two species, one with similar intelligence to humans, but no appendage for manipulating the world around it, and another species that is not sapient, but which has appendages that can be used to manipulate its environment similar to how human hands can be used for manipulating the environment. These two species have an obligate relationship, in which neither species could survive without the other. The ancestors of each of these species has had this relationship for millions of years before one of them evolved the same level of intelligence as modern humans. Let's call the family that the species with sapience is in family A, and the family that the species with appendages is in family B. Each species in family A is adapted to a specific species in family B, and vice verse, so a speciation event in A has always implied an equivalent speciation event in B and vice verse.
What might be the reason that species in family B require a species in family A to survive? How might technology, and civilization develop in this situation, considering that both species are needed for technology, and civilization?