I'm assuming you were referring to survival of the fittest, which is commonly misunderstood to be survival of the strongest.
What survival of the fittest actually means is survival of those most adaptive to change, which is not at all what you are describing.
And if you think he meant human nature, I would say that generally, by nature, humans are kind and share with those they see as their people, but the complete opposite with anyone outside that group. Since the market is made up of people only in the abstract to most people, I would say that that nature doesn't tend toward equillibrium between individuals either.
In any case, there are many examples in nature where a small percentage of the males do a very disproportionate amount of the mating.