Tuesday, April 13, 2010


On page 18, Coyne says that Darwinism can be supported be things he calls retrodictions. He defines them as "facts and data that aren't necessarily predicted by the theory of evolution but make sense only in light of the theory of evolution" (18). Coyne lists that some of the retrodictions that support evolution are patterns of species distribution, how organisms develop from embryos, and the existence of vestigial features. Define in your own words what a retrodiction is. Choose one from Coyne's list and provide examples of it. Why do these fit Coyne's definition of a retrodiction in support of evolution? Are there any other examples of retrodictions that support evolution that Coyne does not list?


  1. Retrodiction uses present theories to explain past events. With evolution being a slow process we can’t exactly test the theory, so we explain why such things as you listed as patterns of species distribution, how organisms develop from embryos, and the existence of vestigial features happened with the theory of evolution. I’ll elaborate this more by going into the details of vestigial features. Vestigial features as Coyne says are, “a feature of a species that was an adaptation in its ancestors, but has either lost its usefulness completely, or… been coopted for new uses”(57). One example of a vestigial feature would be the wings of a flightless bird. Without the theory of evolution, there is no explaining why ostriches would have such a feature. Creationists say that the wings of a flightless bird are still important. They help the ostrich remain balanced, intimidate predators by spreading them, use them to find mates, and as well help with heat control and protecting them from the sun. To clarify, yes, these are useful uses of the wings, but wings are made to fly. Parrots, ducks, geese, and other birds have wings to fly, so what other way other than evolution is there to explain why these birds have lost the capability? Coyne brings up the point that if there was a great creator he wouldn’t give birds wings when he could give them different types of appendages like other animals. If we look at the subject of vestigial features, such as wings, in the evolutionary perspective, we’ll realize the wings of ancestors of flightless birds, like the ostrich, may have been a waste of energy. Flying takes a lot of energy that could be used for surviving and reproducing. According to Coyne, a lot of the flightless birds evolved on islands that “lack of mammals and reptiles – species that prey on birds” (59). These birds would have no reason to fly away from predators then and would have no need to risk injury of their wings by flying. In result, a mutation must have occurred and natural selection took hold, leading to a decrease in the size of wings and the inability to fly. This fits retrodiction because the decrease in wings size or simply the inability for there to be flightless birds can’t be made sense of without some contribution by the theory of evolution. Other features like how some birds have colorful plumage can be another example of retrodiction. Other than looking more beautiful, why would a creator make some birds like the wren very different when it comes to males and females, while others like ducks and geese show little variety in physical appearance? Evolution shows that this developed because wren’s faced more sexual competition than ducks and geese that stick more with their mates. In the process of natural selection, a more colorful wren would have an increased likelihood of finding a mate and reproducing than one that isn’t colorful.

    Why Evolution Is True

  2. I just want to first note that I am looking at the number of comments...currently 0, but we'll see how many there are when I'm done...

    Also, "retrodictions" is a word that Jerry Coyne uses to describe these occurances. This is the word he uses, but not necessarily the entire scientific community. With that cleared up, lets just break down the word. The prefix "retro-" means involving or related to the past (like 'retro'active which means it takes into account what has happened in the past). The second part of the word is -dictions, as in 'pre'dictions. However, these are 'retro'dictions, so they are applicable to the past. They are essentially predictions made after the fact, but apply to and support the theory of evolution. They are scientific findings that, while not necessarily predicted by the theory of evolution, support evolution. Thats pretty much my definition.

    One such example of a retrodiction is the distribution of species on the earth's surface. The distribution of species on the earth starts with the evidence found on convergent evolution. It is known that the earth was not always split into the continents we have now, it actually was one big island called Pangaea. Then, it began to split into the land masses we now see in the different continents. Different organisms inhabited this super-continent, and upon the split, they became separated by a geographic barrier, a lot of water. This kept these populations from interbreeding (which would totally undo any evolution happening). And it led to similar species inhabiting two different geographic areas, but relatively similar areas. This led to convergent evolution. Two separate populations in similar environments, separated by a geographic barrier, evolving into two different, but strikingly similar species. An example of this is in the marsupials of Australia compared with the placental animals of the South America. These two areas, Australia and South America, used to be connected by land bridges in the Pangaea, allowing for the natural migration and spread of the specie. Once these bridges were broken (or burned), these populations of the same specie were separated. However, over the course of evolution with similar pressures, both populations evolved into very similar but separate species. Like the Sugar glider of Australia and the Flying Squirrel. Two very similar species into seemingly different areas. Then, scientists took this a step further and went to Antarctica in search of similar species. Guess what, they found them.

    These is a retrodiction because while the theory of evolution may not have explicitly explained that populations in similar environments would evolve into similar species, it makes sense. Two populations with similar pressures would evolve into the most efficient organism (evolutionaryily) possible. And, why would a creator or designer make different animals on different continents that are so similar? Seems inefficient to me, and as we all know, efficiency means more reproduction and survival....

    Mr. Erdmann
    My good friend, Jerry Coyne.

  3. Retrodiction appears to be a conjunction of two roots, retro and diction; retro meaning to look back, diction meaning to define. This word seems stunningly similar to contradiction, meaning opposite. Instead of contradicting, defining something to be opposites, retrodiction means do define by looking back into history. Since evolution is a time consuming process, it is not necessarily a theory that is experiment-able. We must look back at fossils and past evidence and try to apply the theory of evolution to the changes of animals. Sometimes, evidence may add to our understanding of our working theory. For example, vestigial structures are organs that “no longer perform the function for which it evolved” (Coyne 58), and have been rendered ineffective after evolution, yet have not yet fully exited the body (Covey). For example, the blind mole rat is a rodent that spends its entire life underground (Wiki). It cannot form images which makes the animal fully blind. Molecular evidence shows that these mole rats have evolved from sighted rodents, and they’re eyes are remnants from their ancestors. Eyes are quite a burden for those who cannot use them. Eyes require proteins and require energy to build. They are also quite easily wounded as they are soft and vulnerable. (Coyne 58)The blind mole rats grew a layer of skin that covers the eyes so that they are not constantly using up energy trying to conjure up images that cannot be reproduced anyways due to the darkness of their environment. From this adaptation, we may count this as a retrodiction because the theory of evolution does not directly predict the idea of vestigial organs, but a reason may be deducted from the theory. The fact that a random characteristic may be explained by evolution shows that not only is there evidence to prove evolution, but evolution may also be used to explain other phenomenons, which makes the theory more acceptable and credible.
    Coyne obviously was not able to list all retrodictions, but sexual selection is another topic that Coyne talks about but does not mention as a retrodiction. The theory of evolution itself seems to be a retrodiction, as we are not using new evidence, but past information to develop an explanation for the explanation of the change of species.

    Why Evolution is True
    Wiki: http://en.wikipedia.org/wiki/Blind_mole_rat
    Covey: http://www.creationinthecrossfire.com/Articles/VestigialOrgans.html

  4. Retrodictions are facts that only make sense in light of a specific explanation. For example, if wide spread belief was that the earth was static while traveling around the sun, then evidence suggesting the Coriolis Effect (1) exists would not make any logical sense. In such a situation, there are 2 possible sequences that can occur, either determining that the presented information that challenges the established principle is wrong, or accepting that the information is correct, and modifying said principle. This is exactly what Coyne is trying to prove. His book attempts to show to the world that evolution exists, beyond any reasonable doubt; ergo, the notion of the world, more broadly, the universe, and all its inhabitants being created by a divine being is false.

    Specifically, one of his retrodictions that supports evolution, and also stood out, regarded the "peculiarities of how organisms develop from embryos" (Coyne, P. 18). Creationists/ID proponents believe that humans were specially created (2). However, there are several interesting embryonic and post-embryonic traits that humans have that seem to challenge the idea of special creation. "Human fetuses [...] resemble embryonic fish and reptiles" (Coyne, P. 78). If humans were specially created, it would make no logical sense that throughout development, they would go through several stages, some of which do in fact make a human embryos parallel embryos of other, non-human organisms. Rather, it would seem logical that a human would have his own, unique path of development, if humans are indeed so special.
    Additionally, at approximately six months, human fetuses develop a coat of hair called lanugo. A month before birth, all the lanugo is shed (Coyne, P. 80). Why does a human embryo gain a layer of fine hair, only to lose it a month before birth. It seems like a waste of resources to do such a thing. However, since humans are postulated to have evolved from apes, this observation makes sense. Since evolution remodels what is already there, lanugo was incorporated into embryonic development as sort of "evolutionary baggage." Once again, if humans were the result of an intelligent force, why would they develop with something like lanugo. A waste of resources goes into its development, and then it is lost. It seems logical that an intelligent force would remove all unnecessary body parts/create a specialized pathway for human development. Retrodictions, in essence serve a double purpose. First, they challenge the opposing theory to render an explanation for new, factual evidence. Second, they directly support a different idea. Creationists/ID proponents cannot explain retrodictions like this because they have no factual way to support their claims. Other than saying, "G-d wanted this to be as is," they have almost no way to provide any reasonable explanation. Thus, these retrodictions as provided by Coyne totally and utterly uphold the idea that natural selection and evolution are the driving forces of the change in life/organisms of the world.

  5. Another extremely important retrodiction that goes to prove the truth of evolution is mitochondria found within (among many other organisms), the human cell. Recent scientific evidence suggests that mitochondria were at one point, free living prokaryotes that were engulfed by larger cells (3). If macroevolution DOES NOT occur, like creationists/ID believes, then how is it possible that these free living, single celled organisms became part of the system of cellular respiration in ALL multicellular organisms. Instead of using these micro organisms, why not just develop a different way for macro organisms to perform cellular respiration? Or at the very least, incorporate the same principle of cellular respiration in a different way in organisms such as humans? Though it may be a possibility that the creator wants to trick us into believing that we are the result of gradual change over billions of years, it is highly unlikely that he would do so. After all, would loving parents want to make their children believe that they are not their offspring? However, if this organism (which developed into mitochondria) was the only one capable of performing cellular respiration, it makes sense that larger cells would engulf it, because, they would need a way to produce energy more efficiently. Anything that can do something with more efficiency can devote more resources to survival and proliferation, thus increasing the amount of genetic information that selects for an organism which incorporates mitochondria. If there was no natural selection/evolutionary theory, none of this information would make any sense, since a creator would most likely work differently. Therefore evolution and natural selection must be true.

    1: http://en.wikipedia.org/wiki/Coriolis_effect
    2: http://en.wikipedia.org/wiki/Creationism
    3: Campbell, P. 516

  6. A retrodiction may be defined as the use of presently gathered information to make predictions about the past. According to Coyne, such retrodictions may be used to substantiate the validity of evolutionary theory. Coyne uses several examples of retrodictions such as the “peculiarities of how organisms develop from embryos”. (18)
    Among these peculiarities is the “furry human fetus” as Coyne calls it. About 6 months into the pregnancy, the developing fetus will be convered with a “downy” coat of hair called lanugo. According to Coyne, this is evidence of our primate ancestors whose bodies were covered by insulating fur. Another “peculiarity” is the presence of structures called “branchial arches” in developing fish embryos. Each of these arches contains tissue that may later differentiate into the gills and jaw of the fish. It has been found that mammalian embryos also have such “branchial arches” which nevertheless develop into, among other things, the three tiny bones of the middle ear. Coyne notes that embryonic development “resembles an evolutionary sequence” such that can be used to trace the path of evolution. Coyne notes that the reason the developmental process proceeds in a way that follows this ancestral evolutionary sequence can only be explained in the context of evolution.
    Coyne explains that the reason for such embryonic development is that as evolution proceeds, descendants will “inherit the evolutionary program of their ancestors”. (78)
    Coyne cites “the adding new stuff onto old” hypothesis as a possible explanation for why natural selection has not yet removed these developmental stages during embryonic development. Since development requires biochemical coordination, it is imperative that each structure develop when it’s “scheduled” to. Coyne notes that if ancestral developmental structures were removed in a developing embryo, it might disturb the developmental sequence and hinder the growth of structures that have evolved later in evolutionary time.
    As Coyne claims, the discovery of such “palimpsests” in embryos can be most easily explained and rationalized using the theory of evolution. Coyne claims that to attribute these “peculiar” developmental stages to coincidence would be an explanation far to “simplistic” to be accepted as valid.

    source: Coyne, “why evolution is true”

  7. In the dictionary, a retrodiction is defined as using present information or ideas to infer or explain a past event. From a biological standpoint, this means that new scientific discoveries provide more support for a previously shared theory. While the purpose of these findings is not necessarily in order to prove evolution, they support it nonetheless. On page 18, Coyne includes patterns of specie distribution, peculiarities of embryo formation, and vestigial structures as retrodictions that support evolution.

    Lets take a closer look at the peculiarities of how organisms develop from embryos. It is important to understand that adult species have vestigial structures. A vestigial structure is an organ or structure that is not used in the same way as it is used in other species. Yet, it is not necessarily useless. What is interesting is that embryos have vestigial structures as well. For example, chick embryos which have five-digits in its limbs during development. Comparatively, an adult only has three-digits in its limbs. Therefore, during embryonic development, there are two extra digits that the chick embryo later gets rid of. Another example is in some toothless whales. During development, some toothless whales develop teeth that are later absorbed during embryonic development.

    This all seems useless and a waste of energy, so why does it happen? It is because it is easier to work with what you have than it is to create something entirely new. This is explained by common ancestry. Birds have five-digit ancestors, so during embryonic development they develop five- digit limbs. In the case of toothless whales, their common ancestors developed teeth. Because of this, toothless whales develop teeth as well during embryonic development.

    Therefore, the distinctiveness of how organisms develop from embryos is a retrodiction proving evolution. During embryonic development, an embryo develops characteristics that are not found in adults of the same species. Yet, they share these characteristics with their ancestors. This shows that evolved based off the structure of their ancestors.

    Why Evolution is True by JAC

  8. Retrodictions is compilation of data organized into specific categories. These compilation of data seems to be a data that needs a device in order to understand. For example, it is similar to a messaged code. Although this example may not connect with some of you, it seems to be a perfect match. In light of just looking at the code, the code may not make sense. The reason is because the message of the code cannot be decoded by naked eye alone. However, with the right key, the message can be decoded and understood. However, it is incorrect to say that the theory of evolution is the perfect key for decoding the retrodictions. However, with the theory of evolution as key, biologists can grasp the message that the compilation of data is hiding.

    Now the big theories that contradicts the theory of evolution is the theory of creationism and the theory of intelligent design. One of the retrodictions that I will elaborate on is the idea that "imperfection is mark of evolution, not of conscious design. We should then be able to find cases of imperfect adaptation, in which evolution has not been able to achieve the same degree of optimality as would a creator." (18) Now imperfection of the design would go against creationism and intelligent design altogether. The reason is both creationism and intelligent design allows a being to form a design that should match an organism to its best design. This would prove to be the most efficient and most useful to the organism. However, this is not true. Imperfections of the design of species are found in many places. One example of the design flaw is the nerves that are placed in the front of the retina in the eyes of the human being. The problem is that, although the nerves are nearly transparent, placing the nerves behind the retina would give more clearity to the vision. Then why would humans have that kind of anatomical feature? In light of evolution, one can say that humans did not encounter a significant problem that this problem of nerve chords would affect the survival and reproduction. This shows how few evidences, such as this, only make sense in light of evolution.


    Why Evolution is True by Jerry A. Coyne
    Mr. Erdmann
    Campbell AP Biology 8eth edition text book