To understand artificial selection, one must first understand natural selection. For natural selection, what better place to start than Charles Darwin. He is the father of evolution, the creator of the idea of natural selection, and an integral part in the field of biology as a whole. So I decided to look at Darwin's Theory of Natural Selection, which is broken up into 4 postulates.
1. There is variation among individuals of the same species.
This is especially clear in the human population with our wide range of hair colors, eye colors, heights, skin tones, etc. But it holds true for all species; birds, fish, cows, beetles. Species are not made up of cookie-cutter animals. They are not all mirror images of each other. This is what makes individuals.
2. At least some of these variations are hereditary.
When Darwin was writing On the Origin of Species, words like genes, traits, alleles, and chromosomes were not being used. The field of genetics was in its infancy if even conceived at all. But Darwin, being a bright man and ahead of his times, knew that some how a parent's characteristics got passed on to their offspring. This is essential to the idea of fitness. Being better adapted to surviving wouldn't do any good if you couldn't pass those "variations" on to your offspring.
3. In every generation, there are more offspring produced than can survive.
It is important to understand that there are environmental pressures on species. There are pressures to find food, escape predators, find prey, keep warm/cool, etc. When an individual is better adapted to deal with these pressures and passes those adaptations down to their offspring, they give their offspring a better chance to survive to reproductive age and then continue to pass on those traits. Not everyone is going to survive to pass on their genes though. If you have the adaptive genes, you are going to have a better chance of surviving to reproductive age to pass on those adaptive genes.
4. Natural Selection operates on populations.
The idea that survival and reproduction are not random. Certain individuals with certain adaptive traits are going to survive to reproductive age. This makes those adaptive traits selected for and passed on to the next generation. Being able to survive and pass on your traits shows an individual's fitness.
In the artificial selection of dogs, humans chose what traits are adaptive and are selected for. Great Danes have been selected for their large stature, terriers for the speed, bassett hounds for their long ears, and labradors for their retrieving skills. When you start to play with different breeds like a jigsaw puzzle or a Mr. Potato-Head you end up with some of our more intricate breeds, which I will be looking at this semester.
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