Monday, April 12, 2010

Fossil Record

Coyne describes in detail Carbon-dating. What is the idea behind superposition of different isotopes? Does this produce the relative or actual age of rocks? (pg 23) What do opponents of evolution have to say about such radioactive decay evidence? (p 24)

Coyne claims that the fossil record is important for three main reasons (pg 53). Can you list other reasons that the fossil record is crucial to arguing for evolution (you may elaborate on Coyne’s three points)? It may help to name a few examples of species that support the assertion of the significance of the fossil record in the entire scope of evolution (gradual change within lineages, etc.)?


  1. Actually the law of superposition is different from the principles of carbon-dating as far as the fossil record goes. Geologists define the law of superposition as the layering of sedimentary layers atop the previous one so that something deeper in the earth is older than something that lies above it. It has many notable exceptions including igneous rock that is de facto newer than any rock that it intrudes through and the results of plate shifting disrupt the continuous layer of same-aged rock around the earth. Radioactive isotope dating on the other hand measures the remaining amounts of a constantly decaying radioactive element and based on the known half-lives of these elements, we can determine the approximate age of a rock or fossil. The issue that many religious fundamentalists have against radiometric dating is that we can only directly observe a tiny sliver of time in the perspective of something as old as a rock and we make assumptions that conditions were similar to the ones we have now. Also since the established half-lives of these elements are so long, it would be nearly impossible to test any of them and see if the rate of decay is constant as scientists believe.
    The importance to proving evolution lies heavily in the “missing links” and while Coyne makes a good point that finding every intermediary fossil would be futile and impossible. With the appearance of more and more of these key fossils, more people come to believe in evolution and it could never hurt to be able to illustrate the various paths that organic life took to produce the modern world. Another key point that lies in the ground beneath the deepest fossil layers is the answer to how life first started. If chemical evolution is true then we should be able to see evidence of very complex, nearly organic molecules in deep layers of rock that have not yet become metamorphic due to heat and pressure from the core and also have not been eroded away into sediment. If Darwinists can produce these two pieces of irrefutable evidence then the case for evolution will be an easier one to fight and perhaps it will become more than “only a theory” (Coyne 14).


  2. Carbon dating is one of the elemental procedures to measure the RELATIVE ages of rocks. The reason is because some natural elements have naturally occuring isotopes. These isotopes have a generalized time where the neutron number in the subatomic levels change. One of the most commonly used element is carbon, thus carbon dating. The opponents of the radioactive decay states that the natural occuring isotope's decaying time may be changed due to extreme Earth's pressure. Another point that the opponents of radioactive decaying states that some radioactive dating is wrong. For example, other elements, such as potassium or argon, are inaccurate in some degrees. However, it is stated that radioactive dating give a RELATIVE age and also the radioactive dating does not change even under extreme temperature and/or pressure (Coyne 24).
    Fossils are in many ways important to biologists in the theory of evolution. These fossil records serve as lab data for many archeologists. Because humans have not created a definate time machine, it is hard to find data of species millions and even billions of years old. These data can be found in fossils. One of the reasons why fossil record is crucial for arguing evolution is that the evidence of evolution is from the fossil records itself. For example, the founding of Tiktaalik is a evidence of having a creature posessing both a land-like and water-like creature. This shows the theory of evolution because this shows the gradual adaptation to land, a specific point that evolution argues on. Furthermore, evolution shows the gradual steps, even though not everysingle steps, of chainging within the specie into brancing off. By analyzing morphological and molecular records that the fossils provide, the theory of evolution can be either strengthened or be completely obliterated.


    Why Evolution is True by Jerry A. Coyne

  3. I'm not sure what you mean by the superposition of different isotopes. I you might be combining 2 different ideas, so I'll elaborate on both.

    The principle of superposition states that if a layer of the same type of rock, containing the same type of fossils, appear in two different places, it's reasonable to assume that the layer is of the same age in both places. (Coyne, P.23)

    Radioisotopes are certain radioactive elements that are incorporated into igneous rocks when they crystallize out of molten rock. (Coyne, P. 23) These radioisotopes can then be used to measure how old the rock/fossil is by measuring the amount of it remaining (given the known half life of the element, a natural log function can be used to reverse engineer the age of the rock/fossil).

    So I guess, what you mean is radioisotopes found in different layers of rock. They both produce 2 different ages of the rocks though. The law of superposition can be used to estimate the relative age of a rock. If you have a rock with known age, and then you take a rock of unknown age from approximately the same depth in the earth, it would be reasonable to assume they came from around the same time. On the other hand, radioisotope-dating produces a definite age for the rocks, because everything in the process can be accurately measured. The amount of remaining radioisotope (for example, lets use uranium-235) can be determined. The half-life of U-235 is known. Plug in this with the remaining variables (in depth explanation available here: 1), and you can accurately determine (give or take a few million years) how old a rock/fossil is.

    And if that isn't believable, compare it to a rock sample w/ a known age, and they should end up to be approximately the same (if they are from roughly the depth), thus proving the accuracy of radioactive dating.

    Those who oppose evolution like to say that the pressure and temperature found deep in the earth tampers with radioactive dating (Coyne, P. 24), but as clearly proved with multiple different methods (another can be found in the last paragraph of p. 24 and beginning of p. 25), that radioisotopic dating is, in fact, accurate.

    Essentially Coyne's 3 points regarding the fossil record are those that strongly support evolutionary theory.
    Firstly, the fossil record does show gradual change. We can see this in organisms such as the Tiktaalik roseae (Coyne, P. 36), the transitional forms of dolphins (2), and the transitional forms of whales when re-migrating to the sea (Coyne, P. 50). If there were no transitional models, then there would be no show of gradual change. If that did not exist, then it would be impossible for a reasonable person to believe in natural selection/evolution, because organisms would have evolutionary "gaps." Evidence like that would indeed point to a Creator, because it seems that he would be the only one that can change an animal (along w/ anything else) at will.

  4. His second point discusses how all fossils occur, essentially, in places that make sense. This means that there is a chronological order to fossil. This point is especially important, because if fossils appeared in random places along the evolutionary time line, then the same idea of gradual change would be impossible to accept as truth. After all, if there were rabbit fossils in the Precambrian (when all that existed was bacteria) (Coyne, P. 53), questions like, "How did it get there" would be raised. Evolution would not make any sense if it says that a gradual change is supposed to occur, but random complex organisms sprung up in various places. That would suggest the intervention of an intelligent agent, which would provide proof for ID. However, since everything occurs within the proper time line, with NO exceptions, evolutionary theory must be true since it explains how the organism developed to be in that particular time space.
    Lastly, his third point is about how evolution remodels old structures into new ones. Basically, the same parts are re-used over and over as time progresses, and this is because evolution cannot create. Evolutionary theory is not something, like an intelligent agent, that can do virtually anything. It must "work with what it has." If the fossil record proved to be full of organs, bones, genes, etc. that did not exist in any earlier life forms, then it only makes sense to think that they were created for that specific organism/species. If that be the case, evolutionary theory cannot be the driving for of change in this world, because it cannot create new things, yet there would be proof that it does.

    In addition, ideas like continental drift are also supported by the fossil record. If the world was created and has always looked like it does now, then why are there similar fossils found, dispersed over various continents. However, these are fossils of organisms that could not have traveled the oceans. For example, fossils of the Glossopteris (a plant) have been found on South America, Africa, Australia, and Antarctica. This plant flourished in warm weather, so how is it possible that it existed in Antarctica. Also, how would it have possibly colonized Antarctica in the first place? (Coyne, P. 98-99). If it had been created, why was the same tree created multiple times, instead of just making a new one on each continent, specific to that continent, and able to survive well in that continent. All of these ideas and more only contribute to disproving creationism, and supporting evolution. Truly, how can a tree cross multiple oceans? The answer, the world is not now as it has always been. That is the only logical explanation to this question, and that answer itself helps to improve the argument for evolution.


  5. As Jonathan previously stated, there is a difference between superposition and carbon dating. The law of superposition is founded on the principle of sedimentary stratigraphy, so the deeper in the soil that a fossil is found, the older it is. Carbon-dating uses the radioisotope carbon-14 to compare the quantity a fossil has when it is found and normal quantity of the isotope (what it would have had while it was living.) Yet, carbon-dating only finds the relative age of rocks, just like superposition.
    Opponents of evolution say that the evidence collected from carbon-dating is inaccurate because it does not take into account that there may not be a constant rate of decay of the isotope. In addition, they say that there isn’t an isolated system in which no parent or daughter element and be added or lost and they don’t know the amount of the daughter element present initially, they only speculate. To continue, when carbon dating is repeated with other minerals, the results are not consistent among the minerals giving evolution haters further reason to believe that carbon-dating is a faulty method.
    Coyne states that fossil records are important in proving evolution because they allow scientists to find transitional forms. Much of the proof of evolution is in the fossils because they allow us to see the gradual change of a species over time. Therefore, scientists can apply what they know from the time period to explain what kind of evolutionary pressures these species faced and use that to explain why they evolved.
    The fossil records also permit scientists to find “missing links,” for example the Tiktalik Rosea. Scientists thought that animals evolved for water to land, but they lacked proof. With their previous knowledge, they hypothesized on a time period in which this transitional form would exist. Then, Neil Shubin found the “missing link, ” Tiktalik Rosea. It had characteristics of both land and water species, showing that it was evolving between the two. Even more convincing, after carbon dating, they determined that the Tiktalik Rosea lived around the time scientists had predicted earlier.