Before discussing the rather hefty subject at hand, I believe it is important to know exactly what artificial selection and it's antithesis, natural selection are. I'll try to do this with unique examples and limited use of phrases like survival of the fittest and playing God so please bare with me.
reproduce. In this sense, it seems like natural selection is more like survival of the prettiest, rather than fittest. However, since natural selection ensures that the genetic material of a phenotype that gives a reproductive advantage becomes more common in a population, it's important to note that there are certain traits obtained through the process of natural selection that enable a species' survival.Artificial selection is the selective breeding of certain traits over others. In artificial selection, humans intentionally or unintentionally control which members of a population reproduce or how many offspring they produce, thereby changing the distribution of traits in the population. In artificial selection, it really seems like survival of the fittest really comes into play. Survival of those fittest to amuse, benefit or be eaten by humankind. In writing this bioblog, I found it difficult to find an analogy that would make the above topics easier to understand so I decided to procrastinate and watch tv in true Mary Ward fashion. It was then I stumbled upon an episode of an old tv show, that would become the topic analogy of my bioblog.
Why is artificial selection so common in today's world?
The simple answer: BECAUSE IT'S WORTH IT! The first five minutes of the video is made up of Sam, Carmen and Lily giving reasons for them to dye their hair blond. I found this video very appropriate when speaking of the topic because artificial selection broken down simply is the intentional reproduction of individuals within a population that have desirable traits. Though the girls in this case didn't reproduce with one another, they are altering the traits of their school population to reach a desired outcome and gain a specific advantage. In this case "better grades, boyfriends.....she gets more meat" are metaphors for reasons humans choose artificial selection: profit and fitness for sexual reproduction.
Profit - Many of the foods we eat today are the result of artificial selection. It takes millenia for evolution to produce the results humans desire, so every so often we find the need to speed the process up. Such an example is found in the selective breeding of chickens. Today's chickens are bred to grow larger faster and produce more eggs. This makes it easier to turn a profit selling eggs or the chickens themselves as food products.
Sexual reproduction - Sometimes humans breed animals simply for their reproductive capabilities or their ability to create hybrids. Examples of this are thoroughbred horses and dogs; people actually pay money to have someone else's dog/horse mate with their own animal to create offspring possessing the traits they desire. The creation of thoroughbreds is usually achieved through a hybridization process known as backcrossing between filial generations. Basically it involves crossing offspring generations with p
arent generations to eventually achieve homozygosity.
Among these reasons for natural selection, one more important one must be brought to light by an even more important fact. Motivation for artificial selection is directly tied to our motivation to greater understand genetics. Many of the advancements in genetic fields have been as a result of artificial selection. Take for example Gregor Mendel and his experiments with the pea plants or Adam Nash - the first "designer baby" - and how he was selected to ensure he had the traits necessary to save his sister who had a bone marrow deficiency. Artificial selection continues to be the social norm because we continue trying to understand the nature of genetic inheritance.
In the video above, we are shown what happens when artificial selection produces an outcome that is undesirable from the human perspective. The result - "hair the color of dung" - is known to human beings as negative selection. The video displays negative selection as a result of human error which frequently happens when crops are managed poorly like when humans eat the best cows resultingtly degrading the quality of the cows in follow
ing filial generations. However, with artificial selection, a variety of traits may cause multiple health issues among animals.
Canine Hip Dysplasia, is the example given in the unit guide for a detrimental trait. It is a malformation of the hip joint that hinders a dog's ability to move and eventually damages the cartilage to the point of the dog's full immobility or the point where they need a walking aid. This trait is usually gained by means of genetic inheritance and is commonly found amongst German Shepards, Retrievers, and other above average sized dogs. Under regular circumstances, natural selection would have erased this gene entirely. However, due to selective breeding and breeding practices, it remains within the canine gene pool.
The other examples I talked about in my blog also have their corresponding negative effects. Though chickens produce more eggs as well as bear more meat, they also experience a number of corresponding health issues. Chickens that lay eggs usually suffer from calcium deficiencies that make their bones brittle. Those bred for size eventually become so big with excess meat that their legs cannot support their weight. Both usually result in the chickens being in severe pain as well as unable to walk. With backcross-breeding, it has been found that the breeding of members of a population so closely related could result in the sterility of the offspring. Furthermore, when cows are bred for traits that allow them to produce more mile, they frequently suffer from increased infections and fertility problems.
Conclusion
The topic of artificial selection is such a different one to discuss because of its negative and positive outcomes. On one end of the spectrum it improves the quality of human life by making possible genetic outcomes that would otherwise be nonexistent. On the other end of things, we find that by selectively breeding animals for our benefit, not only do we put their health at risk, but we decrease the biodiversity of their population which could in turn prove to be disastrous later on.
I recognize that my opinion on the topic will be biased because of my personal preferences. I will always love to eat corn, carrots, rice,bread and all other foods that are products of artificial selection therefore I encourage it. However I believe in the practice of artificial selection insofar as it does not jeopardize the health of the animals themselves or cause them any pain. I believe in the use of artificial selection under one additional circumstance: that it be used to ensure the survival of a species of animal such as in the case of the Sanga breed of cattle in Africa which is tolerant to the trypanosomes transmitted by the tse-tse fly that cause nagana disease.
The episode of Popular I included helped me to understand certain aspects of artificial selection we usually don't consider. The most important section of part two was the scene where Exquisite was asked if she wanted to go out with Josh. Though by the laws of natural selection, Josh should have been the obvious choice, sometimes we find laws to be broken. Sometimes random unexpected events occur which make animals with "undesirable" traits more favorable. In the circumstance we find the extinction of animals with desirable trait to mean that of an entire species. Under no instance is this tolerable. Therefore the question of under what circumstances the artificial selection of organisms is allowed is one of whether our roles as stewards of the world should always supersede the role we play as the world's inhabitants.
