Survival of the fittest

While Wikipedia has a good article on the "survival of the fittest", it does not feature a clear, simple explanation of its meaning in the contemporary biological context. It does not mention its meaning from the gene-centric point of view.

Largely synonymous with natural selection, survival of the fittest means the process by which heritable traits survive through generations. Here, 'fit' doesn't mean fit in the common parlance meaning of the word, (such as fast and strong), but possessing qualities, any qualities that increase the chances of reproduction. These qualities may include fast and strong, but also other qualities, such as ability to nurture offspring, the ability to cooperate with others, the ability to convince others, from whom you benefit, of your trustworthiness. The 'fit' qualities will depend on the biological niche of the species concerned, where the ability to produce millions of eggs, or the ability to eliminate potential sexual rivals, or the ability to cooperate with them and other conspecifics, or manipulate them will depend on your species' particular niche. In social species, getting along with others is vital to survival, and this, essentially, is the basis of human morality.

Coming to _what_ survives through the generations, it is obviously not the individuals themselves. No sexually reproducing species produces clones of themselves by this means. Usually, half of the genetic material of each parent goes into the offspring. It's like taking two packs of cards and taking one from card from each in turn to make a new pack. So what survives? Genes and other bits of genetic material (let's just loosely call them all 'genes' for the sake of simplicity). So it is genes that can survive the generations, and it is those genes that can enhance their own chances of being replicated (fit genes) that will tend to increase in frequency in a population as the generations pass. Note that it is not the genes themselves which survive, but the 'information' that is copied when the genes are copied. And here's an interesting thought: It doesn't matter if a gene is copied from the individual himself or herself, or from another individual possessing the same gene.