The phrase: “Survival of the fittest” is confusing. This is because Evolution is driven by environment. The environment, at least over the time it takes for mutated changes to affect evolution, has nothing to do with whether somebody, be it a mouse, a Neanderthal, a leopard, or a tree, is fit. Fitness seems to imply that somehow the being, the organism itself, can survive by improving fitness. This is not the case. This confusion began the easy mis-interpretation that led to the idea of social Darwinism, then pseudo science such as phrenology, then on to such ideas as Aryan supremacy. The idea of a Master Race can be traced directly from such twisting of words and distortion of facts. It has nothing to do with Science.
Let us take the example of Big Cats, as they are critically endangered. It is not because a lion, a tiger, or a snow leopard is not fit that they have died out in most parts of the world.
They are, in those (non in-bred populations) few healthy habitats remaining, strong, agile, graceful and beautiful. As a species, more humans suffering from indoor lifestyle, obesity, and modern wars and car crashes so may be considered less “fit.” Big Cats are extremely outnumbered because, their environment, once a rich and bio-diverse habitat favoring cats, has changed, and is diminished further each day. We have greater numbers, although not better genes.
Another example is the Neanderthal people. They lived and thrived for tens of thousands of years when glaciers covered Europe. They were in this sense “fit” for that kind of brutal environment. As glaciers retreated, another hominid species began to thrive.
Perhaps at first, the Cro-Magnon people were out-numbered by the Neanderthal, but slowly over time, the environment came to favor the new-comers. There is debate as to whether these over-lapping groups inter-married. Since most of us have observed that a human will have sexual relations with almost anything, be it a movie star hottie, or a ham sandwich, it is my personal belief that at least a few Neanderthal traits are handed down through the ages. Mixing of genes produces new variations, and environment, a good season or a harsh one, an earthquake or a flood, a meteor impact, or a slow glaciations affects the population within it. When traits are inherited that favor the new variations, just one drought or disease will seriously impact an entire group.
Many believe that far from being the “fittest” of the two types of hominids, it was the harsh northern climate and the fierceness of the robust and stocky Neanderthals that kept our later group out until relatively, quite recently. When the climate favored our kind, we jumped right in.
Survival of the fittest, as Darwin used it later, was coined by Herbert Spencer, a British Philosopher. Had either of the two men realized how the terms would come to be mis-used and made murky by sloppy interpretation, and even hostile defensiveness, it is doubtful they would have chosen that particular phrase.
In fact, in may be said that the phrase itself “Survival of the Fittest” is not likely to survive the modern environment of Biology. We now know how strongly supported this “theory” of evolution is, and more accurate and favored terminology is holding strong. Scientists prefer the original term Natural Selection. It has been determined to be the more “fit” of the phrases in a more enlightened, and therefore, favoring, environment.