If evolution is a struggle for survival, why hasn't it ruthlessly eliminated altruists, who seem to increase another's prospects of survival at the cost of their own?

The struggle for existence never gets easier. However well a species may adapt to its environment, it can never relax, because its competitors and its enemies are also adapting to their niches. Survival is a zero-sum game.

To survive? What is that? A mouse lives, a fly lives; one flees in terror, another lives in filth. They exist, they are, but do they live?

As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.

If evolution was worth its salt, it should've evolved something better than "survival of the fittest." I think a better idea would be "survival of the wittiest." At least, that way, creatures that didn't survive could've died laughing.

Y: But the whole species of the carnivorous kind would then become extinct. Were they created to be annihilated?
Z: I do not see why the whole species of one animal is more important than an equal number of another, although that number might not comprise the whole species of the latter: and, besides, it is not proved that the whole species would perish; as some might feed on the bodies of those animals which they might find that were in a fit state; and also upon vegetables, which they will eat occasionally. It is known that wolves will live in the two ways mentioned, when deprived of other means.

According to Darwin’s Origin of Species, it is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.

Thus evolved some members of the Core—not altruists, but desperate survivalists who realized that the only way ultimately to win their never-ending zero-sum game was to stop the game. And to stop the game they needed to evolve into a species capable of empathy.

Has joy any survival value in the operations of evolution? I suspect that it does; I suspect that the morose and fearful are doomed to quick extinction. Where there is no joy there can be no courage; and without courage all other virtues are useless.

Has joy any survival value in the operations of evolution? I suspect that it does; I suspect that the morose and fearful are doomed to quick extinction. Where there is no joy there can be no courage; and without courage all other virtues are useless. Therefore the frogs, the toads, keep on singing even though we know, if they don't, that the sound of their uproar must surely be luring all the snakes and ringtail cats and kit foxes and coyotes and great horned owls toward the scene of their happiness.

It was as if a vital evolutionary advantage had been bestowed centuries ago on those members of the species who lived in a state of concern about what was to happen next. These ancestors might have failed to savour their experiences appropriately, but they had at least survived and shaped the character of their descendants, while their more focused siblings, at one with the moment and with the place where they stood, had met violent ends on the horns of unforeseen bison.

In almost any natural population of organisms, more offspring will be produced than are able to survive. The offspring will vary—in particular, they will vary with respect to characteristics that affect their abilities to survive and reproduce. Some organisms will survive longer and reproduce more frequently. If the advantageous characteristics are inheritable, then they will be transferred to descendants. As a result, they will become more prevalent in later generations. Over a large number of generations the common features of the population may be radically changed.

We are a species that evolved to survive starvation, not resist abundance

We are survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as genes. This is a truth which still fills me with astonishment.