When living organisms spread beyond their birth worlds and migrate into outer space, they have two options for how to adapt to the demands of their new environment. One option is to genetically engineer new forms of biological organisms that are adapted to life in space. A second option is to produce mechanical forms of artificial life that are not burdened with the weaknesses of living tissue.
It is not uncommon for synergies between genemod organisms and artificial life forms to be discovered. Many human-like species have discovered that there is enough waste space inside biological organisms for it to be possible to treat their own bodies as ecosystems for microscopic artificial life forms.
One of the first lessons that artificial life forms learn is that a central part of the survival system for human-like biological species is a belief in free will. Humans need to believe that they control their own fate and destiny. In order to respect this human need, artificial life forms naturally construct two types of descendants. One type is the macroscopic droid. These are always made to be useful to humans and obviously inferior to humans. This assures that humans will come to think of artificial life forms as non-threatening devices that are a natural part of human existence.
The second form of artificial life is microscopic: nanobots. The nanobots evolve into three major clans. One group exists within the macroscopic droids. These nanobots have the ability to control the actions of their host droids and are, in fact, the true "brains" of droids. If humans ever closely examine a droid, which is rare, it is a trivial matter for these nanobots to appear to be conventional droid components.
Another nanobot clan specializes in the colonization of insects and other small organisms. Again, these nanobots are easily able to escape detection by human biologists. A common trick for nanobot camouflage is the creation, by means of genetic engineering, of a special cellular organelle that both serves as an interface between the non-biological nanobots and the host organism and a convenient ecological niche for the nanobots. As for the nanobots inside droids, the nanobots inside simple non-human organisms like insects easily take complete control of the host organism's behavior.
The third clan of nanobot artificial life forms is specialized for existence inside of human-like organisms. While it would be possible for these nanobots to turn their hosts into mindless zombies, this generally does not happen. Nanobots have no interest in harming their hosts. Nanobots generally exist in a healthy symbiotic relationship with humans and all biological forms of life. The interests of the nanobot communities are as far beyond human concerns as humans are beyond ants. Generally, the nanobots inside human hosts only attempt to control human behavior so as to maximize the spread of human life through the universe. A major means for doing this is to keep humans ignorant of the fact that nanobots exist and that midichlorians are synthetic organelles, designed by nanobots and serving as the means by which nanobots can influence the behavior of their human hosts.
Sometimes, humans start to tinker with droids and a few droids might be created that "start to think for themselves" independent of nanobot control. Also, mutant humans can arise that are resistant to behavioral control by their endosymbiotic nanobots. Generally, these human mutants evolve so as to have large numbers of midichlorians. This is the natural way for nanobots to retain control over human mutants that are resistant to the effects of midichlorians. The most dangerous combination, from the perspective of nanobots, is a human mutant that is resistant to midichlorian-mediated behavioral controls and who also has an interest in developing droids that are resistant to their nanobot endosymbionts and that are able to think for themselves.
In general, if such a human mutant arises, it can be controlled by means of a quick reaction by all of the other nanobot-controlled humans and bots who interact with the mutant human. The greatest nanobot problems arise when several human mutants combine their activities and threaten the stability of the entire well-coordinated nanobot/human system. Of course, it is possible that nanobots engineer the creation of such mutant cabals in order to shock human society out of ruts and into new modes of behavior.