What ever benefited the family benefited the species and so the development went over the millions of years. In evolution anything that gives a species an advantage and can be passed on to offspring will generally cause that species to flourish and continue. There is also another factor not commonly understood that is often the difference between success and failure over the long haul. This has been called by some as the doubling factor. What it means is that often a single factor that initially gives a species an advantage in a given niche is not enough to insure its long-term survival.
Competition is fierce on all levels and especially on the evolutionary level.
An advantage that is here today may often be gone tomorrow when a competing species also develops a similar or even better strategy. But if after securing the first advantage, a species comes up with that one in a billion second advantage immediately after the first one, it greatly increases the species long-range prospects. In fact, it may be that this Doubling Factor is responsible for much of the improbable long-term success of niche dominating species. This is exactly what happened to the Eppie's. First they developed a fast mobile life style that allowed them to get to an underutilized food source.