Once upon a time I had half an idea to leaverage this fact for a story involving genetically engineered pygmy marmosets. They were modified to have human brain

Once upon a time I had half an idea to leaverage this fact for a story involving genetically engineered pygmy marmosets. They were modified to have human brain structure but retaining their size. Ideal crew for space missions. Fast forward to a time when they dominate space and seek independence.