Just because our human bodies have these particular hands, it doesn’t necessarily follow that they are the only kinds of hands our brains could ever be good at using.
While it is true that our brain’s parietal lobe provides massive computational machinery for assisting in manipulating objects with our hands and fingers, it is not necessarily true that the parietal lobe evolved only for these particular human hands, with their five jointed digits and single opposable thumb.
Evolution is parsimonious, since it proceeds via a kind of haphazard hill-climbing algorithm. It’s much more economical (and reachable through the random walk of evolutionary steps) for a brain to encode a set of general procedures for individual learning, than to hard-wire into our neurons all the particulars of specific grasps and gestures.
We see something similar in spoken language. Human children have evolved to learn any language that follows a common set of procedural rules, not any one specific language such as Japanese or Serbo-Croation.
This loose coupling suggests an intriguing possibility: As our technology continues to advance to the point where we will be able to have the sensation of physical manipulation — as well as gestural communication with each other — using whatever bodies we choose, perhaps we will evolve those virtual bodies in various ways.
It might be more useful to have tentacular fingers, or two thumbs on each hand, or something even more radically different. In a sense this question comes down to understanding the functional set of learnable procedures encoded in our parietal lobe, since any modification to our virtual bodies that is not supported by our brain’s hardware will not gain wide acceptance.
There is certainly precedent for looking at such things. In particular, something analogous has happened throughout human history in the evolution of musical instruments. The variety of extant musical instruments is vast, yet no instrument will survive from one generation to the next unless our brains can control our hands when playing that instrument. In a way, the corpus of popular musical instruments serves as a kind of functional roadmap of our brain’s parietal lobe.
If, after mastering the underlying technology, we manage to “physically” evolve the virtual bodies with which we will communicate in cyberspace, that will lead to all sorts of fascinating questions. For example, I wonder what it will mean for the future evolution of musical instruments.