"Research on the interaction of human genetic and environmental influences had once been limited to hypothesis and statistics. The homunculi changed that. Drugs or other treatments could be tested in vivo, and adverse affects noted before the patient suffered them.
They were genetically human, aside from scaled down growth and development. Their neural complexity was far too limited for intelligence. They had some basic responsiveness to stimuli - flight, ingestion and procreation - and like flatworms could be trained to a minimal degree of problem solving, but in testing they measured far below rats. A resemblance to their full-sized genetic twins seldom caused researchers any permanent compunctions.
Once the wealthy and famous began to keep precautionary stocks of their homunculi, the interest of hobbyists was inevitable. The "huncs" were marketed as "Living Dolls". Personal genotypes were protected, of course, but semblances of political or entertainment figures could be bred in less than a year, and toy companies provided the accessories and costumes.
Prosthetic neurons were a second medical advance, designed to replace damaged brain tissue. They acted like a virus, attaching themselves to white blood cells for delivery to the injured area, infecting damaged neurons, and replacing them with a carbon-based superconducting network. Charge efficiencies limited the replacement structures to a centimeter or two, but when combined with retraining the therapy was very effective in cases of stroke or other localized damage.
The initial studies had been done on homunculi, of course. The resulting chimerae - homunculi with a non-cellular "brain" - could be programmed with remarkably elaborate behaviors. This meant little to the medical researchers, but the Eldee market went ballistic. Customers could receive not only a specific type or likeness, but a matching repertoire of behavioral sets. The Historical Figures educational line provided a "Winston Churchill" who walked with a characteristic stride and chewed on an imitation cigar. "Sally Rand" was supplied with both fans and fan-dance.
As saleable behaviors became more complex, the industy co-opted the knowledge-base platforms created for gamers or fantasists. These already existed in program form, and the slightly increased rate of defective behaviors was balanced by speed of manufacture and access to short-term marketing opportunities.
No one stopped to calculate that the prosthetic neurons, replacing nearly the entire homunculi cerebellum with a structure elaborated to the quantum level, would reach complexities equivalent to the human brain."
from Trooping All Together: An Historical Retrospective