Stuff You Should Know - How Evolution in Isolation Works

Episode Date: May 15, 2008

How does isolation spur evolution? Check out this HowStuffWorks podcast to learn more about speciation and evolution. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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only I can see you. What you're doing is larger than yourself, almost like a religion. Like, he was a god. Listen to The Turning Room of Mirrors on the iHeart Radio app, Apple podcasts, or wherever you get your podcasts. Brought to you by the reinvented 2012 Camry. It's ready. Are you? Welcome to Stuff You Should Know from HowStuffWorks.com. Hey there, welcome to the podcast. I'm Chris Pallette. I'm one of the editors here and with me, as always, is Staff Writer Josh Farr. Hey Josh. How's it going, Chris? Doing okay. I thought we would talk about what happens when animals evolve in isolation and basically it starts with the theory of evolution and how we're all related. Exactly, yeah. And like you said, you hit upon as a theory.

I think we should say that not everyone subscribes to evolution, but if you're a scientist, you most likely do. There are a few ways to go about evolving and one of them is through evolution and isolation. For that to happen, you have to go through a speciation event. And what that is is just when one species becomes two or more species. For example, bears. You want to talk about bears? Sure, we can talk about bears. Okay, well the black bear is the parent species of the polar bear. It makes sense if you think about it. They're bears, right? So surely all bears are related. But how do polar bears become white? Why are black bears still black? I think evolutionary biologists tend to believe that it was because of a peripatric speciation event. And peripatric

speciation occurs when a species becomes so spread out geographically that members in different areas are living in different environments, undergoing different experiences. So the black bear up north had a fur coat that stood out like a sore thumb against the white landscape, the snow covered landscape. So they evolved to be white. That's not enough. That doesn't cover speciation entirely. For speciation to be complete, you have to go through reproductive isolation. And this just means where the members of species no longer can produce offspring. It can be because they develop different genitalia. It can be because they've developed different times of the year to mate, different locations to mate in. Either way, if reproductive isolation occurs, a speciation

event has taken place. Okay. So basically, they just have to be different enough where they're no longer able to reproduce with one another and then gradually become a different species altogether. That's exactly right. And there's also some other really interesting aspects to evolution. One of them I know you know a lot about. That's the evolutionary bottleneck, right? That's true. This is when a group gets completely or I guess nearly completely cut off from the main group. So they are reproducing only with one another. It's like a bottleneck, if you think like a soda bottle. But that can cause some problems because if there's a genetic defect, it can be passed down from generation to generation. You mentioned in the article a group

of Amish people in Pennsylvania who had a trait for smaller than normal brains, microencephaly. And that can be fatal. So obviously in this case, this very small group of people having that trait be passed down was fatal to that group. Not a desired trait either. No, definitely not. But you know Josh, one of the other examples that you used in the article that I thought was really cool was the iguanas that were displaced by Hurricane Maryland. And that's sort of an evolutionary bottleneck. And it's also an example of a different kind of speciation allopatric, which is they're cut off by a geographical boundary. In this case, they're on an island separated by the main group by water. And the small group of iguanas floated from Guadalupe

to Anguilla. And I think that's really cool because it's a completely scientific study. There are no or there were no iguanas on Anguilla before this happened. It's a completely natural experiment. Right, right. You know, it wasn't forced. They just happened to notice that these iguanas are going to go there. And so they found out, we're going to find out if there'll be a bottleneck. And also the island rule, which is funny that this is an island. But yeah, the island rule would give them a chance to see if these iguanas will grow larger or smaller as a result of being cut off from the main genetic body of iguanas. So it's going to give scientists a chance to see evolution up close and personal,

as it were. Ironically, it was a gift from God to conduct a natural experiment on evolution. There you go. Well, you can read all about this in what happens when animals evolve in isolation on howstuffworks.com. For more on this and thousands of other topics, visit howstuffworks.com. Let us know what you think. Send an email to podcasts at howstuffworks.com. Brought to you by the reinvented 2012 Camry. It's ready. Are you? On the new podcast, The Turning Room of Mirrors, we look beneath the delicate veneer of American ballet and the culture formed by its most influential figure, George Ballangin. He used to say, what are you looking at, dear? You can't see you. Only I can see you. What you're doing is larger

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