[Squirrelloid]

well, acquiring 4 *functional* arms would be really hard for a vertebrate, since hox gene screw-ups are generally fatal.

The indian example was a co-joined twin, and thus the extra limbs were almost certainly non-functional.

Now, in 50 years we might be able to build (genetically) something with 4 functional arms. Whether its actually useful or not probably depends on what else we can do.