Cladograms---I don't get them.


Off-Topic Discussions


I grew up reading and absorbing anything and everything I could on paleontology, and am still happy to call myself a armchair version of one. But, like others my age (49), I learned about the evolution and relationships between species using the classic "family tree" motif.

Now, there's this thing called the Cladogram, with taxons, crown species, sister taxons, etc. Assume you're talking to a 6 year old, and please try to explain how to read and understand them to me.

Thanks...

What a drag it is being old...


*dusts off that birds and mammals class from college and brushes up on wiki*

You know how people like to argue on the rules forums about whats ostensibly an objective set of rules but what comes down to mostly arbitrary judgement calls?

This is like that, but with "your criteria are entirely arbitrary" instead of yo mamma slams.

They're trying to see how closely species are still related to each other. A big problem is that there's three very separate ways of doing this, which is probably whats confusing you.

Monophyly- The way you're familiar with. The closer the common ancestor, the closer you are together. Clean, ostensibly simple, and more or less testible with genetics.

The downside- If your great great great grea great grandpappy was a lizard, you're still technically a lizard no matter how much you change which brings us to...

paraphyletic- Is a group of organisms with a common descent Minus some groups you feel fell too far from the tree. For example, reptiles are a paraphyletic group because if you want to include everything we call a reptile you need to go so far back that you also include the ancestors of birds and mammals. So we just snip birds and mammals out of the group and don't invite them to the family picnic.

Polyphyly- Is a group with a shared characteristic. For example birds and mammals are both warm blooded even though our most recent common ancestor probably wasn't. Sharks and dolphins are both finned swimmers, and sharks and celocanths are both "fish" despite the celocanth being more closely related to us than to sharks.


Ok, that makes more sense, now.


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Let me start off by saying this is one of the Best Threads ever.

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Do we have to use them only for animal ancestry?

I've never heard of Cladograms and I'm learning from reading wiki right now. It seems that we can use them to track the way the rules of D&D have evolved too.

( Someone smarter than me must start a new thread and use Cladograms to log the D&D rules' divisions over the last 30 years? )


Jail House Rock wrote:

Let me start off by saying this is one of the Best Threads ever.

-----

Do we have to use them only for animal ancestry?

I've never heard of Cladograms and I'm learning from reading wiki right now. It seems that we can use them to track the way the rules of D&D have evolved too.

( Someone smarter than me must start a new thread and use Cladograms to log the D&D rules' divisions over the last 30 years? )

Linguists use them too, though I'm not sure how accurate they are.


Jail House Rock wrote:

Let me start off by saying this is one of the Best Threads ever.

-----

Do we have to use them only for animal ancestry?

No, but they tend not to be as useful outside biology, due to multiple inheritance.

Quote:

I've never heard of Cladograms and I'm learning from reading wiki right now. It seems that we can use them to track the way the rules of D&D have evolved too.

( Someone smarter than me must start a new thread and use Cladograms to log the D&D rules' divisions over the last 30 years? )

There's an issue there, though. In general, a biological family tree only diverges, and never converges. That is to say, once two groups have divided into separate species, they'll never rejoin into a single one, so you never have to worry about some sort of chimera that's one-third lion, one-third snake, and one-third goat. (That's not true when we're dealing with individuals and subspecies groups; it's possible to be half-Irish and half-Norwegian, of course, just as it's possible for dog to be half Alsatian and half Dalmatian, and a lot of math has gone into looking what happens at the edge cases there...)

That's not true for game rule sets; d20 Star Wars is, of course, half D&D 3.0 and half WEG Star Wars. So cladograms don't make as much sense because a single game can have a half-dozen ancestral lines.

While the same thing should be true for linguistics, the folks who study this stuff cheat in order to pretend that languages are also single-inheritance line. That's why English is considered a Germanic language despite the fact that more than half of the vocabulary you find in the dictionary comes from Latin or other Latin-based languages.

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