Charles Darwin (1809-1882) is famous for developing a way for evolution to occur, natural selection. It should be pointed out that when Darwin was alive there was no question that species evolved. Scientists in general all agreed that the species that were alive around them did not remain fixed forever and ever, but rather changed over the course of long spans of time. The problem was that no one could figure out how this took place. Darwin made observations of the natural world and noticed four simple features that would result in species changing in response to the natural environment. The process of change that Darwin proposed occurs as an inevitable consequence of these four conditions, and does not require any divine influence. The four conditions that Darwin elucidated were variation, heritability, superfecundity, and non-random mortality.
Variation means that that each individual in a population is unique. These differences may be very minor, but they are always there. This is so obvious a fact that it almost does not need to be spelled out. You are a unique individual who has never occurred before and will never occur again, and the same is true of every other species.
Heritability means that each individual will tend to pass on the variations it has to its offspring. In this way, the variations that are present in a population will tend to be passed down through the generations. In other words, short individuals will tend to have short offspring, etc. This heritability is not perfect, in most traits, because there is mixing between the traits of each parent.
Superfecundity means that more young are produced than can possibly survive. Each individual strives to pass its genes on into the future. To accomplish this, the more offspring produced the better and since all organisms use this strategy, a great many offspring are produced. This leads to competition among unique individuals for a limited number of available resources needed for life.
Non-random Mortality means that how dies matters. Many organisms die, and this is especially true of young organisms. This is driven,in part, by the competition mentioned above and, in part, by factors such as harsh weather conditions and other environmental factors. But while it is a foregone conclusion of superfecundity that some individuals will die, it is the fact that these deaths do not occur at random that allows for population-level changes to occur. In other words, the survivors survive for a reason, and the reason is that they have some advantage, however small, over those that did not survive. The survivors are then able to pass their advantages, whatever they are, on to the next generation.
After generations and generations of this combination of conditions, populations of individuals become evermore adapted to the environments in which they live, and so evolution by means of natural selection occurs.
abirdingnaturalist 
A nice, clear non-argumentative presentation. I wish more discussion of Darwin was this calm. I recall from reading Origin of Species a couple points that he stresses. One was that variation and heritability are so obvious in domestic selection–farmers selecting certain varieties of crops, breeders selecting varieties of animals. (That’s why we all have so many types of apples, along with filet mignon.) In describing domestic selection, he sets the stage so persuasively for the natural version. Also, about superfecundity and mortality, Darwin’s dark emphasis on struggle–given all the competing offspring in every situation, he saw a world of living things all struggling so intensely. Any variation that gave the slightest advantage made a big difference. Anyway, your smart selection of the four categories prompted my recollection. Thanks.
Artificial selection was a huge part of the Origin, I agree. Darwin figured that if he could convince people that lineages could change under human direction (which as you say is obvious), it would be easier to convince people that the same thing could happen naturally. And I certainly agree with you that Darwin had a pretty “red in tooth and claw” view of competition and survival. It would have been interesting to get Darwin’s take on the evolution of cooperation. Thanks for reading my blog!
“It would have been interesting to get Darwin’s take on the evolution of cooperation.”
It’s just another adaptation, not a separate condition alongside the three basic facts of inheritance, variation and superfecundity. Cooperation is another path to deal with competition for finite resources. I don’t think it’s a challenge to Darwin’s “dark” view at all. I’m not speaking for Darwin here, I’m only pointing out that, in my understanding, the appearance of cooperation, does not call into question Darwin’s basic argument. What would stop nature from selecting cooperative behavior alongside predatory behavior? (We kill more animals than any predator in history. There is no more successful killer than H sapiens—save catastrophic natural disasters, I guess. We’ve domesticated and raised entire species so we can eat them. That is a form of cooperation between species, too, though not a pleasant one if you’re a chicken or a cow or a pig or a fish that was born so a predator could eat you. We also kill far more animals than we would ever need for mere survival.) Nature is rich with all manner of attempts to survive—I think the “dark” aspect of it isn’t that everything is trying to kill and outlive everything else, but rather that organisms, species and ecosystems are all determined by those three basic facts: variation, inheritance, superfecundity in finite resources in highly contingent environments. (These facts are also contingencies based on other facts, too, I guess, like…molecular biochemistry, quantum physics, etc, which themselves might be contingent—but now I’m reaching the limits of pretending to know what I’m talking about.)
TL;DR: Cooperation is probably a strategy in the struggle for survival. Also, cool blog! I very much enjoyed this post and will be reading others. Thank you.
You are such a good teacher!! Thanks professor!! Parcheezie
Or maybe we could put it like this: cooperation is a way to compete.