This to me is a case of evolution, but we need to be clear on what is evolving. Evolution works at both the individual and the "deme", which is defined as population that breeds only within itself. These two forms are frequently in conflict as changes that favor an individual may well decrease the overall viability of the deme (this is an example of the Prisoner's Dilemma).
The evolution of intelligence creates a new dimension for evolution. Evolution for non-intelligent species consists basically of modifying the hardware, the physical construction and development of the organism. This is roughly equivalent to the early days of computer where "programming" consisted of physically changing the connections in the computer. Intelligence, however, allows the development of culture which is the equivalent of software so that behaviour can be modified without any genetic or physiological change. This means that behaviour can radically changed within a generation or two, enormously faster than any previous type of evolution. As long as the underlying individuals are sufficiently intelligent the exact level or distribution is not particularly relevant to the culture.
The key point is that the benefits of a "good" cultural can be propagated without any genetic continuity. This is one of the key wonders of the United States, that it acknowledges this at a basic level. This is part of the superiority of American culture because it can maintain itself by "colonizing" new hosts (immigrants) far easier than other competing cultures. We need only make sure that the rate of assimilation is greater than the rate of immigration. This can be done either by restricting the inflow or increasing the rate of assimilation. That's something to keep in mind.