Borg
From NSwiki, the NationStates encyclopedia.
The Borg are a cybernetic collective consiousness that could be described as posthuman although that is not exactly accurate as they can assimilate any species and thus are better described as post-sentient.
The Borg cannot reproduce in a biological sense and instead assimilate other beings into their collective through the use of nanotechnologoy. Many Borg nations may also resort to cloneing/genetically engeneering a population.