Sunday, March 11, 2012

Cool Evolution Stuff: Ring Species

Evolution doesn't really have anything to do with religion, except that many people decide that it doesn't mesh with theirs and they deny it is real without ever learning how it works. It is really a shame because many religious people do believe in evolution. It seems totally reasonable to me to believe in both and I wish more believers would be willing to follow the evidence where it leads.

I have never studied evolution formally, but I do find in fascinating and read about it now and then. Some of the things I read about are really cool and I thought it would be fun to describe them here. Hopefully I will get all of the important details right, but as I said I have never studied this formally so I might make mistakes. If I do please point it out.

Today I want to talk about ring species. Before I get into why I think ring species are so cool, I want to talk a little bit about speciation. There are a few different ways that speciation can occur, but I want to talk about something that was described in "On the Origin of Species" (It might have been "The Selfish Gene", I read them at around the same time a few years ago).

Let's say you have some type animal who lives in one particular place, let's just say it is all the way to the west of a large land mass. This animal is doing very well and starts spreading out over new territory to the east. Even though the animal is all over the place on this land mass, the animals to the far west and the animals to the far east do not breed with one another. There is breeding all through the continent, so there is some gene transfer, but generally the animals from the west and east can have separate genes and the ones in the middle are hybrids.

Now, let's suppose there is some kind of selection pressure which is different east and west. Eventually you might get animals well suited for the east and other animals well suited for the west and the in between animals wouldn't really fit well in either setting and will eventually die off, giving you two separate species.

I remember when I first read this little hypothetical story I wasn't really sure what to make of it. It seemed to make sense well enough I guess, but I wasn't sure I completely followed why the genes from one side wouldn't just propagate to the other and it didn't really make sense why the middle species would die. For the first thing, I think I wasn't thinking of a large enough land mass, and the second, there are a huge number of reasons why a population of animals might die.

So anyway, I had this situation sitting in the back of my mind somewhere, and then I read about ring species, which seem to be this process in the middle of happening, but there is also a twist, the extremes live in the same place (or maybe just nearly the same place?). Let's say you have a species that lives in a mountain surrounded by a valley, such as this salamander. As we go along the mountain range around the valley there are different populations of the animal. Any two adjacent populations can interbreed no problem, but the populations from the beginning and end cannot interbreed.

This is really cool for a couple of reasons.
1. Are the salamanders the same species or not? They can't interbreed so we should say no. However, there are 19 populations of the things that can each interbreed. So population 1 and 2 are the same species, pop 2 and 3 are the same, etc, but then pop 1 and 19 are not the same. The point is, our definition of species is a little fuzzy.
2. Suppose a bunch of the middle populations died out before we thought to look for it (say populations 4-17). We would just see 2 separate species of salamander in the same place and not think too much about it. This is a really neat demonstration of how new species could form.

That was fun. I hope I got most of the details correct here. At the very least, I hope it is clear why I think ring species are so cool.


  1. This is such a cool phenomenon. Like any hypothesis, evolution is beyond a hypothesis, evolution can make accurate predictions of what we would expect to see and is also falsifiable. For example, if we found an animal we didn't expect to see long before it would have arose according the the theory, this would probably debunk evolution. The old example is finding a rabbit fossil in the Precambrian. Ring species are something that follows along with evolution. I'm assuming you've read this example by Dawkins, but whether you have or not, I am going to put his explanation here. If we go back one generation at a time in our own ancestry, step by step, hypothetically the genes of a parent and an offspring are close enough to breed. If you took a time machine and went back a hundred generation. You could probably breed with that person. If you go back another hundred generations, you might still be able too. There does come a point when the genomes are no longer compatible because they are simply too different.
    Skipping ahead to ring species, from my understanding, this kind of follows the same idea. The further "apart" its been since they've breed and interchanged their genomes

    An after note. I once saw a long list of examples of things that if found, would disprove evolution to use as examples. I tried to do a search and found this. I started reading it "10 reasons evolution is wrong." This guy (or gal) clearly doesn't understand evolution and is just trowing out so many ignorant statements. If I didn't know anything about evolution and only read this article, I would discount it right off the bat. He also ignores a lot of solid evidence. Look at the part about "primitive atmosphere." First he says that evolutionists claim that life came form spontaneous generation or from space. Evolution makes NO such claims whatsoever about the origin of life. See abiogenesis: He says that amino acids would have been wiped out by sea water. (he then quotes an article over thirty years old in scientific american. Our understanding has come a lot further since then). He says that the organic compounds that formed in nature would be destroyed by oxygen. (We know that oxygen levels were WAY lower and almost non existent on our primitive planet. Oxygen was a byproduct of primitive animals). Not all life requires oxygen. Relatively recently, a breakthrough is finding MULTIcellular life that doesn't require oxygen. A quick google search for "life that doesn't require oxygen" brings up a lot of results. The first prokaryotes that arose did not require oxygen. He then quotes some scientific american articles as old as the 1950's. He goes on to say that because we are "unsure" that disproves evolution. (see my note on abiogenesis) I did a quick search on Abiogenesis on youtube (videos are easier to watch than reading long articles sometimes.) And this was the first result. I haven't studied organic chemistry yet, but this is one of the leading ideas on abiogenesis. It seems very plausible. watching it, it was nice to see some of my points emphasized :) (This person also uses better analogies than I did though. It's a good ten minutes, and was a tad hard to follow since I don't remember much of high school chemistry, but still worth a watch.)

  2. That's a good point. The way the ring species is spread out in space is similar to the way many species are spread out in time. So it does a good job demonstrating something that is hard to imagine because you have to think about how thing change over time, but you can see it at one time through space.

    "For example, if we found an animal we didn't expect to see long before it would have arose according the the theory, this would probably debunk evolution."

    I wanted to clarify this a little bit. Evolution is a very large very complicated set of ideas. If you found an animal in the wrong spot like you said, it wouldn't debunk evolution wholesale, but it would question some things and there would be refinement. That is really the power of the scientific method, if makes predictions and when things fail the predictions it is examined and refined.

    and yeah, it is hard to watch people who spout garbage like that who really don't understand things. When I was a kid I was subjected to much of that kind of thing and thought it must be obvious that evolution is BS. If I had never come across the real information and learned how to look things up and more importantly, to question my assumptions, I might be one of the people repeating this garbage. It's scary to think about.

  3. Actually you are more correct in your point about "refining" evolution. It would be quite a big change.

    I often worry myself about repeating bad information. When I am corrected about something, I try to pass that on to anyone I've told but sometimes its hard to do. Often I've told my girlfriend something, then a week or so later found out I was wrong and then corrected myself. She is usually like "Wait. What are you talking about?" One of the liberating thing about being an atheist is that you don't have to know. You can learn and go based on the available evidence. It's okay to be wrong. Just admit it when you are, learn and move on. :) When I was religious, it was like I had to be right, because my church was infallible and nothing can change that. I know I'm making an assumption here, but maybe the strong connection and people getting offended has to do with not "being able to be wrong." If that even makes sense.

  4. That completely makes sense. I have felt the same thing, after leaving religion and feeling that it is ok to be wrong, I feel liberated.

    I've also done the same thing as you with my wife, I will tell her things that I read about and later find out I was wrong. Sometimes she will question my sources and we will look it up. I really love that. Often times I will have some detail wrong that activates her bullshit detector. After she points it out it seems obvious that I read something wrong and we go back to the source, even though when I first read it to myself it seemed reasonable a second reading will fix my mistake.

  5. That's so awesome! Sometimes its hard for me not to get embarrassed for being wrong, but I try to keep in mind that life is a learning process. I try not to feel bad because sometimes the source I got it from believed it too or was wrong. I wish that what you were talking about was more of a general attitude with the public. In political discourse for example, it seems to be dominated by this "my side is always right, your side is always wrong" mentality that seems so destructive to the whole process. When a politician admits to being wrong or changes his mind about something the media and the other side are quick to jump on them and discredit them in general. I'm not referring to flip flopping on issues because of whats popular here, but more coming out and admitting "you know, I had this stance one this issue, but after learning more, my stance is now otherwise."

  6. I totally agree about the political discourse thing. I think it is one way in which the news media is doing serious harm to the country. They go for the sensational news story above everything. They make it impossible (or at least extremely difficult) for politicians to say "I was wrong, here is what changed my mind"

    As for being embarrassed at being wrong, I feel that too. I try to learn to just laugh at myself when I make a mistake. It can be especially embarrassing when it is something you have said a lot. I recently learned that the whole space pen/pencil thing is a myth, but I've repeated that one to a lot of people, oops.


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