On pages 125-128, Coyne discusses natural selection as it relates to breeding, or artificial selection. He provides examples, such as dogs and turkeys, of species that have been bred by humans to select for specific traits.
Do you think that breeding could lead to speciation and evolution eventually? If so, how? Does breeding interfere with the idea of "survival of the fittest," or does it enhance it? Feel free to consult any outside sources.
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I do believe that breeding does lead to speciation and evolution. For example, Coyne brings up that all dogs, "every single one... descends from a single ancestral species" (126). Coyne then continues in stating that "humans began to select about ten thousands of years ago" certain dogs for certain traits, and we see today over 150 different species of dogs.
ReplyDeleteSelective breeding in some examples can interfere with "survival of the fittest." Continuing with dogs, we see some examples of dogs today that are really not viable in nature. For example, during the reproduction unit, we saw a movie where the chihuahua was mentioned as an animal that could not give birth without humans giving them a c-section. Therefore, in someways, selective breeding creates some species that would never have existed in nature without human intervention.
Like Frank, I also agree that breeding leads to speciation. It even states in the book that there are over 150 different species of dogs today descended from one common ancestor, all with unique traits that define itself as a species. Plants are another example of how breeding leads to speciation. The process is described in pages 815-816 in the Campbell book, when a plant with desirable mutations are found, the plants are crossbred with the original, and the offspring are bred again with the original. This continues until only the desired trait remains. This also holds true for bred animals; those with desirable traits are bred until that trait is expressed without any other traits. In fact, artificial selection speeds up speciation, either reducing the time process or creating more branches of species than normal within a set time frame. This relates to the theme of Continuity and Change. As the ancestor of the modern dog bred, it gave birth to certain mutated traits that early humans found desirable. However, instead of changing over a long period of time, breeding allowed these slight changes to become dominant traits within a relatively short amount of time. As Coyne states in his books, all modern species of dogs “…have been selected in less than ten thousand years, only 0.1 percent of the time that it took wild dog species to diversify from their common ancestor in nature” (126).
ReplyDeleteWhile it is true that breeding at times is contrary to “survival of the fittest,” there are also cases where traits bred for humans also coincided with traits that are helpful for better survival. Using another example from the book, “Look, for example, the greyhound, which was selected for speed, and wound up shaped very much like a cheetah” (127). Coyne describes this as an example of convergent evolution, where similar selective pressures lead to similar outcomes.
I agree with both Kevin and Frank that breeding leads to speciation and evolution. On pages 126-127, Mr. Coyne explains that by breeding dogs, humans have made different types of dogs. Mr. Coyne explains that "some variation was produced by genetic mutation that could be inherited." Breeding leads to different species that may have not resulted without interference. I however don't agree that breeding of animals leads to evolution. Humans are interfering with the survival of the animals and therefore are interfering with the idea of the survival of the fittest. Animals are now surviving because humans are allowing them to, not because they have the right genetic material to survive in the environment.
ReplyDeleteFrank provides a good example that isn't able to reproduce because of human involvement. The chihuahua isn't able to give birth because its body is too small to give birth to a liter without help from machines and humans. Another example of dogs not being able to survive without human involvement due to breeding is that dogs can't survive for food without the help of humans. Wolves, the closest ancestor of dogs, don't look for humans for help even if the wolves were brought up by humans. Dogs on the other hand, rely on humans for almost everything including food, shelter, and warmth. Dogs genetic material has changed so that the dog doesn't know how to survive without humans due to human breeding of dogs as pets (http://www.futurepundit.com/archives/001944.html).
Even though breeding of animals may not lead to evolution, breeding of plants may. When humans breed plants, the humans are breeding the "best plant." The humans usually breed the biggest plant that would provide the most nutrition. Humans usually breed the biggest plant because that plant is desirable for agriculture and is able to survive in its environment. The humans pick the plant that will be the most likely to survive and be able to produce for plants. In this example the breeding doesn't interfere with the idea of survival of the fittest (Campbell 815).
The concept of breeding relates to the theme of continuity and change like Kevin had said. Continuity and change is defined by Campbell on page ix as when "DNA molecules carry biological information from one generation to the next." The desired genes, in the opinion of the human, are breed into the new organism. The genetic material is being transferred into the next generation so more organisms will have that same DNA.