Providing evidence for evolution

Last week I pointed out some common misconceptions about evolution and arguments that  are often used to support creationism. This week I would like to share some of what I feel to be the strongest evidences for evolution. I feel like too often in debates about evolution the focus seems to be on refuting creationism instead of correctly presenting evolution – and the science is really awesome. With the evidence I present here I seek to answer the following questions:

What is the fossil evidence for evolution?

What can we learn about evolution from living animals?

Does evolution present any testable predictions?

What is the fossil evidence for evolution?

One of the common arguments against evolution is “where are the transition fossils”. This is perhaps the weakest of all arguments against evolution. The transition fossils (or casts of the fossils) are available in every reliable natural history museum. Wikipedia has an extensive list of transition fossils. These fossils include the human evolution of Australopithecus to Homo Habilis to Homo Erectus to Homo Sapien. They include evolution of invertebrates to fish. They even include the evolution of insects.

The fossil evidence is extensive, and the argument that we don’t have fossil evidence is tired. Creationists quickly say things like “just show me the transition fossils” or “where is the missing link”, but we actually have quite a bit of fossil evidence. Just this last week Dr. Steven Novella wrote a great article on feathered dinosaurs – an excellent example of transition fossils.

Unfortunately, each time new evidence of this type is presented creationists treat the new fossil like the hydra from greek mythology – finding one transition fossil just creates two new transitions whose fossils haven’t been found yet.

What can we learn about evolution from living animals?

The Laryngeal Nerve

An interesting evidence for evolution is the laryngeal nerve – the nerve that supplies motor function and sensation to your larynx. If you were to design the nervous system in an obvious way the laryngeal nerve would leave the spinal chord somewhere in your neck and travel directly to the larynx. Instead, the laryngeal nerve leaves the spinal chord at the neck, travels down into the chest, wraps around an artery leaving the heart, and then travels back up the chest, up the neck, and finally ending at the larynx.

This odd path is even more exaggerated in a giraffe, where the nerve travels 15 feet out of the way to wrap around the heart and return to the larynx – only a short distance from where it originally left the spinal chord.

 

So why does the nerve take such a convoluted path? Evolutionary theory describes an ancestor to all vertebrates much like modern fish. The same nerve in fish takes a much more direct path from the spinal chord to the larynx. As evolution progressed, the laryngeal nerve was caught on the wrong side of the heart. With each generation, natural selection lengthened the neck and with it the laryngeal nerve.

Ensatina

A second modern day example of evolution is the Ensatina of California. These salamanders live in a ring around the Sierra Nevada mountains and give an interesting example of speciation. Where does one species end and a new species begin?  A simple definition is that two animals are different species if they are unable to breed fertile offspring.

In this example, the salamander with the red label interbreed with the salamander with the yellow label, the yellow interbreeds with the blue and orange, and the blue interbreeds with the pink. However, the pink does not interbreed with the red. It is safe to say that the pink and the red salamanders are different species – but where did the speciation occur? Evolution does not happen in large jumps. It happens slowly, with changes every generation.

Does evolution present any testable predictions?

One important qualification of a scientific theory is that any new idea must provide some testable hypothesis. How can we know that we aren’t just deceiving ourselves if we can’t test the ideas we’ve come up with? So, does evolution provide any testable predictions?

Human Chromosome 2

Chromosomes are highly condensed structures made of deoxyribonucleic acid (DNA). DNA, of course, being the key building block of all life. DNA stores our genetic information.

Human chromosome 2 gave a testable hypothesis for evolution. If apes and humans truly have a common ancestor, then we should have the same number of chromosomes. As it turns out, we do not have the same number of chromosomes – humans have 23 pairs and apes have 24 pairs. This is actually a big problem for evolution as a viable theory. If at any point a chromosome was spontaneously lost or gained it would result in serious consequences (either miscariage, or a phenotypic disorder like Down Syndrome or Turner Syndrome). Evolutionary biologists predicted that at some point a chromosome fusion happened (that is, two chromosomes combined into one large chromosome). In this way, no genetic information would be lost and a difference in chromosomes would not disprove evolution.

As it turns out, human chromosome 2 is a fusion of two chromosomes. There are four telomeres (which begin and end a chromosome) and two centromeres (which are found at the center of a chromosome). Of course, showing that human chromosome 2 is fused is not enough to prove that we have a common ancestor with apes. However, this evidence is strongly supported by the identification in chimpanzees of exactly which chromosomes were fused to create human chromosome 2. To me this is a home run for the theory of evolution.

Conclusion

There is strong evidence for evolution, but just as my previous post was in no means a complete list of all the arguments used to refute evolution, this post in no way contains all the evidence. In fact, it’s probable that I left out some of the most compelling evidence (and I’d love to hear them in the comments). However, in writing this article I chose the evidence that I see as the most compelling.

About Chad Jones

Hi! I'm Chad Jones, a PhD student studying physical chemistry. I also write/manage a science blog. Please check it out! http://www.thecollapsedwavefunction.com Also, feel free to e-mail me: chad@thecollapsedwavefunction.com
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23 Responses to Providing evidence for evolution

  1. The argument over the imaginary lack of transitional fossils is a classic example of Xeno’s Paradox. Fossil A is described as the ancestor to fossil Z. Creationists ask, “where are the transitional fossils between A and Z?!” No matter how many times a transitional fossil is found “filling the gap” between two species, the creationist can always point to “gaps” between the new species and the old. For example:

    More fossils are uncovered and Fossil A is described as the ancestor to fossil M which is the ancestor to fossil Z. Creationists ask, “where are the transitional fossils between A and M?!”

    More fossils are uncovered and fossil A is described as the ancestor to fossil F which is the ancestor to fossil M which is the ancestor to fossil T which is the ancestor to fossil Z. Creationists ask, “where are the transitional fossils between A and F?!” Continue until the end of the Earth.

    The fallacy is obvious. Not every generation of every species is fossilized. In the real world there will never be a 100% complete chain of transitional fossils directly linking, A, B, C, etc… all the way to Z.

  2. Scott says:

    The transition of purpose of the bones in the ear are another great example I’ve always liked.

  3. Eric Hall says:

    I always like the Peppered Moth example http://en.wikipedia.org/wiki/Peppered_moth_evolution

    • Tom says:

      It’s amazing to me that the peppered moth example is STILL being presented as evidence for evolution! This is an example of natural selection ONLY, one that fits wonderfully within the Creation model as well.

      In order to demonstrate evolution, you must show that prior to the observed change, there was NO genetic code for a feature in question (in this case ‘dark’ wings), and that the environmental pressure caused the genetics for that feature to be produced via mutation. Simple changes in existing gene frequency isn’t evolution AT ALL.

  4. Carmine Fragione says:

    There is no empirical proof to say the Telomere Fusion is fact, except in Cancer Research . So, you have to borrow from the failure rates theory and then yet not explain how two lesser chromosomes fused, but the product has more genetic sequences than the two lesser , had before the fusion . That is just confusion,

  5. Carmine Fragione says:

    You can tell a story in reverse. The ancient common ancestor was actually a human mother with 46 chromosomes. The Y chromosome for the male sperm had a 40% deficiency of genetic information , that broke a chromosome in the Gamete called a Trisomy, and the surviving zygote began a sub species, offspring leading to the apes as devolved. You say three groups , orangutans ,gorillas, chimps ,had 48 , but humans also had three groups, Homo Sapiens, 1. Modern 2. Cro Magnon , 3. Neanderthal if they all had 46 that is a statistical tie that the common ancestor was just as likely to have 46 or fewer chromosomes to start with , and not the 48 you claim must be true. So, you have no specific evidence of the ancient common ancestor or it’s DNA to argue from, you have nothing.

  6. Tom. says:

    The case presented discussing the salamander interbreeding is really not significant. It is yet another example of data that supposedly supports evolution, but just as well if not better supports the creation model. The creation model adheres to initial existing capability, which can be lost over time. If you isolate groups long enough, over time they can lose the ability to interbreed. What evolutions tout as ‘new species’ and ‘progress’ is actually in fact the LOSS of capability. This in truth can just as likely, if not better, support the creation model.

  7. Aziz says:

    Transitional fossils don’t prove much. Were you there when they transitioned? However, there is a lotta evidence for God; it is in the Bible.

    • Scott says:

      How does that statement even make sense? Were you there when the various authors wrote their passages for the bible, or when the events they describe actually took place?

      How does an actual physical solid hold-in-your-hand fossil provide less evidence than a collection of stories written by people who weren’t even present at the events they describe?

      • mud says:

        They like being humored Scott..Clearly Aziz isnt any sort of authority (even at the school science level). He just likes the kicking from time to time.

        We recently saw this with a medico who became a religious crank elsewhere on Skeptoid blogs. I’d ask;

        Show me the bit about arithmetic you understand. We could fill out a spread sheet of competative notions versus evolutionary sciences and current Biology, chemistry and physics. But lets just start with arithmetic…

        The transitional fossil jibes usually hide a whole raft of blancmange that underlies a misunderstanding of sciences. You’d have to be a fanatic to carry that amount of blancmange around.

        The same holds for any tenuous proposition.

        • Scott says:

          yeah, I know. When I replied I knwe I’d be “feeding the troll”, but it just one of those absolutely ludicrous statements (how do you know, were you there?) that I don’t know how they can type it without falling off the chair from laughing so hard.

          • Moral Dolphin says:

            Creation garble is a recent fashion that the indolent parade. Never tell them they are on a cat walk. They will think you have taken the monkey out of them.

            its just a poor excuse so they can justify racism, religious bigotry and homophobia on weekend nights. Educational snobbery isnt in their domain..

          • Aziz says:

            It is true. It says so in the Bible. Why would the holy book say it is true unless it is not true? Why would an awesome God lie to his followers? Evolution is just a theory. Creation scientists, on the other hand, have proven creation theory just by quoting the Bible.

  8. Tom says:

    These “Transitional fossils DO exist!” claims by evolutionists are made out of ignorance of how big this problem really is. Evolutionists certainly enjoying listing all of their ‘candidate’ transitional fossils, but the truth is, they’re all weak candidates. Every time the ‘best’ examples are presented, further researched on these determines that they really aren’t significant after all.

    For example, read this article: http://www.icr.org/articles/view/4546/274/, particularly the 3rd paragraph where it says “…the reality is that it does not contain a single universally accepted transitional form. Every transitional fossil candidate has both proponents and doubters even among evolutionary ‘biologists and paleontologists.’ “

    Evolutionists call challenges to fossil transitions ‘tiresome’, but get used to it. It IS a problem regardless how long this list of weak candidates is.

    BTW, here are a few more articles:
    http://creation.com/refuting-evolution-chapter-3-the-links-are-missing
    http://creation.com/missing-links-parade
    http://creation.com/punctuated-equilibrium-come-of-age
    http://creation.com/refuting-evolution-chapter-3-the-links-are-missing
    http://creation.com/that-quoteabout-the-missing-transitional-fossils

    • Abdulaziz says:

      Creation.com sites….wow that is really wonderful. You are
      so truthful dear. Thou shall not bear false witness. How long will
      you spread lies and distortion of facts?

    • Abdulaziz says:

      TRANSITIONAL FOSSILS: This is for the educated people.
      http://en.wikipedia.org/wiki/List_of_transitional_fossils All other
      uneducated people may rely on other sources that hate
      Evolution.

      • Tom says:

        Amazing irony! Only uneducated people believe in that list (http://en.wikipedia.org/wiki/List_of_transitional_fossils). Do the research on that list. It’s NOT accepted within the community of paleontologists.

        For a more detailed reason to reject that list, consult “The Fossil Record” by Dr. John Morris.

        Again, amazing irony, because only uneducated people believe that list!

        • Abdulaziz says:

          A book by John Morris, are you kidding me? Why would I read a book written by a creationist on Evolution? If you have watched John MorrisWatch Francis Collins, Kenneth Miller, (scientists and Christians) on what they have to say about Evolution. Read up on vitamin C gene mutations in mammals, some fish and reptiles. Read up on Chr 2 fusion in Nature magazine, read up on transitional fossils found almost everywhere, Read up on ERVs…..and stop acting like a village idiot. Stop distorting facts.

        • Abdulaziz says:

          Not accepted by palaentologists…..Jesus Christ! You truly are not well educated. You are breaking one of the 10 commandments: thou shall not bear false witness.

        • Abdulaziz says:

          Here is the AMAZING irony for the uneducated people who pretend to know more about science than scientists themselves. http://www.paleosoc.org/evolutioncomplete.htm

  9. Joe says:

    Can chromosomes fuse naturally – this is a huge fundamental change, what could spark such a change? has this been proven that it can happen naturally ?

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