Friday, April 9, 2010

¡Viva la Evolución!

On pages 125-128, Coyne addresses artificial selection in the form of plant and animal breeding. He explains that all modern domestic dogs are most likely a descendant of the Eurasian gray wolf, and through breeding humans have created 150 breeds that are recognized by the American Kennel Club.

Give another example of an animal or plant that humans have transformed for their own needs or desires. Do you think that through breeding humans are meddling with natural selection and disrupting the evolutionary process or is this just another factor influencing evolution. Explain and provide strong support for your opinion.


  1. Artificial selection is essentially us providing pressures to different organisms in order to make them mate and reproduce. This can produce entirely new species, or just amplify the expression or suppression of certain genes that could be beneficial to those making it happen. This is also called selective breeding in animals and is in no way rare, especially on farms.
    As Grace has already mentioned, the 150 breeds of dogs all evolved from a common ancestor, most likely the Eurasian gray wolf. However, because of breeding wolves with different genes being expressed, new breeds of dogs arose. Then, humans would breed these new breeds as well, creating even more different breeds. While this may have been done to find physically appealling dogs as well as domesticated breeds, other animals have been selectively bred so that they express certain characteristcs more. Then, we exploit these changes. Coyne provides the example of the svelte wild turkey. Previously wild, these turkeys have changed a lot during domestication. The turkeys have become more "docile, meaty, and virtually tasteless" as well as developing breasts "so large that male domestic turkeys can no longer mount females" (Coyne, 127). Because we have bred the turkeys with the most desirable traits for us, they have changed so drastically that they depend on us to help them reproduce and they cannot do it natually anymore.
    Another farm animal that has been selectively bred are chickens. However, there are two different types that have been bred for. First, egg laying chickens have been bred for. These lay more eggs than normal chickens, and mature at a normal rate, allowing them to lay eggs longer. This was done by breeding the chickens that layed the most eggs generation after generation. Also, other chickens have been bred to be extra meaty. These chickens grow larger in about have of the time. Therefore, the most meat can be taken after slaughter, and they can be slaughtered earlier. Both of these examples of selectively bred chickens benefit us rather than the chicken.
    Selective breeding is disrupting natural selection and evolution, but not that much more than regular domestication. As mentioned above, domesticated turkeys can no longer naturally reproduce and depend on us to do it for them. However, regularly domesticated animals depend on us as well. They depend on us for food, shelter, and protection from predators. Regular domestication interferes with natural selection because the species dont have to deal with evolutionary pressures on their own. I dont feel it is necessary that we stop though because animals provide us with a very necessary source of nurishment and we help them survive, up until they are needed ;).

  2. There are numerous other examples of artificial selection. For example wheat and corn were both originally much smaller but through centuries of human breeding have doubled or even tripled, if not more, in size. Similarly, oranges, apples, and bananas have all been selected for size and taste. In fact, most of today's fruits can not reproduce without human interference and would die out if not for human cloning.

    In my opinion humans are not interfering with natural selection as humans are a species of the plant and so co evolution between humans and plants and animals is expected. While it is true in many cases humans breed animals consciously and specifically for a purpose, but because humans provide for these plants as long as the plants provide for them the relation can be seen as a symbiotic one and is similar to others found in nature such as the mycorrhizae of many plants. Similar forms of co evolution are found all over nature. As Coyne himself brought up there is the example of the Asian giant hornet and Japanese bee (112). Attacks by the bee has brought about a response from the bees (evolutionarily speaking), and while it is true that the bees do not consciously attack the bees to elicit this evolutionary adaption, they are forcing the bees to adapt in order to survive. Similarly humans force adaptations that benefit them in exchange for the guaranteed survival of the animals/plants being breeded.

  3. Domesticated cats are another form of animals that humans have brought transformed for their own needs/desires. Cats have been with humans, at minimum, for 9,500 years. During the course of this time, humans have adapted felines for aesthetic purposes, and as hunting companions (1).

    In a sense, humans are meddling with evolution. The primary force behind evolution is natural selection. Natural selection, as summarized by Richard Dawkins, is the "non-random survival of random variants." Basically, selective pressures force an organism to adapt to them or die out. If the organism dies out, then its genetic information is void. However, if the organism adapts, then there has been a mutation in the genetic information of the organism. This mutation, may occur in any part of the genetic code, so long as it properly adapts the creature to the selective pressure. The concept of natural selection drives change in organisms, but how that change occurs is in fact totally random.
    Humans on the other hand select specific trait in organisms to proliferate. This type of selection induces a pressure onto an organism, where an intelligent agent determines what genes they want to be proliferated. The same selective pressures are repeated in multiple generations to increase the strength of display in the gene. Eventually, this gene becomes so strong that every generation of the organism displays a certain trait.
    Given that a certain specific gene is selected and modified by induced pressures, artificial selection is different from natural selection. Animals subject to the pressures of artificial selection are still evolving, but not as they would had there been no intelligent agent. Therefore, humans alter the course of evolution.


  4. Many domesticated animals have been affected by the forces of artificial selection and selective breeding. For example, pigs have been bred to be very fat, producing maximum meat per pig. Similar breeding for certain advantageous traits has produced modern horses (speed), cows (milk/meat production), and dogs (cuteness/trail scenting) ( Artificial selection has also altered the traits and even caused the speciation of certain plants. For example, "farmers have cultivated numerous popular crops from the wild mustard, by artificially selecting for certain attributes" ( These crops include: cauliflower, broccoli, cabbage, kale, and kohlrabi; all these crops were created through different alterations made to the wild mustard plant by artificial selection. All of these plants have been selected for so that they could be cultivated for nutrition. While selective breeding may not necessarily be natural selection, one could argue that it is a selection process leading to adaptive evolution because, after all, organisms selected by humans for certain traits are able to fill certain "niches" that satisfy human needs, thus allowing its genes to be passed on further. Artificial selection may not choose for traits that would help an organism survive in the wild, but it does increase the value of that organism to human society, thus allowing it to survive and reproduce under human care.

  5. While many are quick to point out how unnatural many human activities are, from an animal standpoint one must remember that we are doing as any other species do: we exploit our environment in order to promote the survival and reproduction of our species. In Michael Pollan's book The Botany of Desire, Pollan argues that human selection of the wild grass that produces corn is due to the nutritional benefit that it provides us, as opposed to nuts from trees, which have evolved to benefit squirrels. Because of this benefit, our society has cleared millions of acres of land once inhabited by trees in order to plant corn, which provides more of a benefit to our species. This is a completely natural occurrence from a biological point of view. Although we did not breed corn to create its delicious fruit/vegetable, we have chosen to promote the survival of its genes over those of the trees in the area. Pollan also discusses our genetic influence over the apple. In the apple's case, not many people know that the red delicious, the common apple, is from clones from all the same original tree. A plant from Kazakhstan, every apple tree produces different apples, in appearance, taste, and many other facets. The red delicious comes from a tree that grew in the 1920's, and the man whose yard it grew in become a rich man. Once he realized how tasty the apple was that came from his tree, he let fruit companies graft it, or take a sample of the wood from his tree in order to plant a new tree with the same DNA. Since then, our red delicious tree genome has not evolved because we use the same clone every time. This is great for industry, but as we know from biology class, pathogens that wish to invade the tree for parasitism are constantly evolving new ways to accomplish this feat. Because we have stopped the evolution of most of the apple trees through "human selection," we may face an uncertain future for the apple tree which has stopped evolving defenses to defeat these pathogens many years ago. We cannot think of our actions as against evolution, just against it by natural selection. Our presence as a species is so influential that we promote evolution through a different mechanism: our own choosing.