I must point out one slight problem with the proposing of the 'genetic theory' for such things on here. Firstly, as identified previously by some intelligent individual, evolutionary theories (i.e. genetics) generally require some 'need' or ill adaptation to be developed overtime, this means if such were genetic it would most likely be limited to one specific power (such as levitation) and not a wide range.
Sorry for the off-topicness, but had to correct this. Evolution and the process of natural selection do not pander specifically to the needs of a population - a random mutation happens, and if it is advantageous, the member(s) of the population with the beneficial mutation will get more mates and thus the mutation will propogate, and the previous "model" will be removed from the population's gene pool. The mutation at the beginning is random - there are far more useless mutations which just die out. They do not necessarily pander to needs. Note 'necessarily' - coincidence can sometimes create an answer to the need.
In relation to your argument, you're still right that only one would probably be developed, but more might be developed at the same time, just far less likely.
Alone again...