Monday, April 5, 2010

Remnants and Creationism

Vestigal traits are discussed starting on page 56 and explained as a trait that "no longer performs the function for which it evolved" (page 58). The example of an ostrich is given because it does not use its wings to fly however it does use them to balance when running and as a warning to enemies. Therefore how is it decided that the wings are a vestigal trait of the ostrich since they are indeed performing a function? How is it decided that the wings did not evolve to help balance the ostrich instead of flying? What are the criteria for a vestigal trait? What are the criteria to classify a trait as an atavism?Then discuss how creationism discards vestigal traits as support for evolution. 


  1. Ostriches have been deemed as flightless birds. Though it is true that the ostrich do use their wings for balance, they no longer serve the main purpose of wings. Wings have the main definition of "either of the two forelimbs of most birds and of bats, corresponding to the human arms, that are specialized for flight." ( The wings of ostriches may have been deemed as vestigial because they do not aid the animals in flight, which is the main and assumed role of wings. These "wings" of ostriches might as well just be deemed as balancing stubs.

    It was not decided that wings are not an evolutionary advantage. These wings just no longer serve their purpose. Vestigial traits are coined as "any diminished structure that previously had a greater physiological significance in an ancestor than at present" (Theobald). The wings no longer aid in flight and thus have lost significance and was deemed as vistigal.

    Atavisms are "Atavisms are traits of distant ancestors that reappear in the modern day." (Lambert). Atavisms include the reappearance of legs on dolphins, who have finally evolved to lose their legs. It is not yet known why atavisms happen, but the answer is said to lay in embryos, since embryos may develop characteristics in in the embryo that disappear soon after.

    Atavism may be described by creationists as simple mutations. Since they do not believe in evolution, reverting to past ancestral traits is also against their teachings.

    (page 2 also used)

  2. The wings of an ostrich are considered to be a vestigial trait even though they indeed still perform a function. The reason that for this is because the wings “no longer perform the function for which [they] evolved” (58). Like Aaron said, a standard definition of a wing is "either of the two forelimbs of most birds and of bats, corresponding to the human arms, that are specialized for flight." ( As we know, ostriches are birds that can’t fly, and hence it seems as though their wings are unnecessary because they can’t carry out their function. However, these wings still serve a purpose in balance and defense so it’s advantageous if the ostrich has them, as opposed to having them eventually disappear through the forces of natural selection (Honolulu Zoo). Since a new use has been established for the ostrich’s wings, it is likely that this will enhance the survival and reproduction of the ostrich and so the wings “will be maintained by natural selection, though in a form that doesn’t allow flight” (Coyne 59). The role change of the wings might have certainly evolved just for this purpose. The only reason the wings are now classified as vestigial traits is because their original function is no longer being carried out. They are no longer necessary for flight because they have taken on different roles in an ostrich’s life.
    Like Coyne stated, atavism is a “throwback trait produced by the occasional reawakening of ancestral genes that have long been silenced” (Coyne 56). After a period of absence, a certain trait can recur by chance. A prime example of this is the whale. According to the standard phylogenetic tree, whales are known to be the descendants of terrestrial mammals that had hindlimbs. Thus, we expect the possibility that rare mutant whales might occasionally develop atavistic hindlimbs. (Macroevolution). It is a totally random process and has no connection with natural selection and choosing traits that prolong an organism’s survival.
    Vestigial traits can commonly be associated with atavism but there is a distinct difference between the two. Vestigial traits arise when the original function of a structure changes, and atavism is when a structure disappears and then returns, without any change to its function. Ativism does not support evolution nor natural selection because it occurs by chance, with the occurrence of random DNA changes, as opposed to gradual changes that are done purposely to enhance the life of an organism. In the eyes of creationists, the return of past ancestral traits or the change in function of a specific trait is not possible because they don’t believe in evolution and gradual change. (Macroevolution) (Honolulu Zoo)

  3. Vestigial traits are traits that serve little to no function on present forms of an animal or organism that were active and useful for previous evolutionary forms. In the case of the ostrich, it has wings that do not serve their intended function: either of the two forelimbs of most birds and of bats, corresponding to the human arms, that are specialized for flight. Although they do not serve for flight, they are still very useful in balance of the ostrich. I don't think one can explicitly label an ostrich's wings as a vestigial trait then based on the definition of a vestigial trait, which claims the trait is not useful. In this case, the wings are extremely useful. The wings may have developed for balance in this case because evolutionary pressures may have made it more advantageous for the ostrich to remain on the ground but keep its wings for balance when running, chasing prey, or any of numerous activities. However, the wings of the ostrich are still classified as a vestigial trait because they do not perform their original function, flight.
    Atavism is the recurrence in an organism of a trait or character typical of an ancestral form and usually due to genetic recombination. This is the idea that a trait found in previous ancestors lost in evolutionary change may appear again in modern forms of that animal. This can be seen in the whale. Whales are said to have evolved from land animals, such as the hippo. Atavism in whales would perhaps be the development of legs. This process is a random mutation in DNA and therefore, does not support natural selection (in the sense of a gradual change due to survival of environmental pressures). Creationists do believe in mutation, as it can happen in humans where we get several forms of diseases. However, they would not go as far to say that a mutation would result in the appearance of past evolutionary traits that have become extinct since they do not believe in macroevolution- that organisms can dramatically change into new species (ie. that a whale would show legs because it evolved from land animals).
    Why Evolution is True