Brain damage can lower intelligence, and I see no reason why it could not be raised as well. Even if genes provide something "defaults" or "limits," environmental effects are still relevant.
Are you really suggesting that brain damage can increase intelligence or just suggesting that intelligence can be raised?
It is pretty pointless talking about if intelligence can be raised or not unless we actually define what we mean by intelligence. In the absence of a tight definition all we end up doing is arguing about what each of us thinks intelligence is.
