It’s a Bird/Dinosaur!

Well, I got the recent news about that feathered dinosaur. Apparently Ken Ham and other Creationists have declared it to be 100% bird despite lacking a bony breast muscle anchor birds have and possessing dinosaur features like clawed fingers and teeth. This brings me back to a point I was thinking about including in Creationism is in a State of Chaos, though I rewrote it partway through to cover bigger issues, rather than list miscellaneous details. I’ve seen some Creationists claim that the more famous archeopteryx was all bird. I’ve seen others claim it was all reptile/dinosaur. It will not surprise me if this latest fossil triggers more flip-floppery from Creationists trying to shoehorn it into the categories they’re comfortable with.

The evolutionary answer doesn’t necessitate glossing over contradictions. It’s a theropod dinosaur that has evolved some early bird features. All birds are theropod dinosaurs, since they descended from theropod dinosaurs. They’re a subcategory that developed identifying features on top of the ones that define theropod dinosaurs. All birds are theropods, but not all theropods were birds. Inheritance and polymorphism are important concepts here. Theropods beget theropods by the rule of inheritance, but new theropods can have traits that are unique to them, which is polymorphism. One branch of theropod descendents evolved traits on top of the theropod template that we use to define what a bird is. Those theropods that possess some bird traits but not all of them are a part of the transition from the general category of theropod to the specific category birds.

One big problem with Creationism is that its proponents are trapped in Platonic idealism, treating “bird” as if it were defined by some ideal independent of the actual feathered creatures making tweeting noises outside my window. Evolutionary taxonomy starts with the actual organisms that existed and defines them based on their features and how they’re passed on. Platonic Creationism looks at the creatures that exist now and try to define past creatures based on modern categories. It’s kind of like trying to assign the telegraph to the category of smart phone or desktop computer. All three are electric devices that communicate to others in a binary code. The telegraph lacks the numerous features that define the other two categories, so it doesn’t fit into either.

Aside: The invention metaphor isn’t a good fit for evolution in general, since you can move features horizontally across branches. Smart phones are phones, but they’re also computers because some people thought it was a good idea to add those computer features to a phone. When organisms do seem to copy a different branch, you can pretty much count on the copier doing a superficially similar end result in its own distinct way instead of simply copying and pasting DNA from the other branch. Living organisms larger than a handful of cells generally don’t borrow features from other branches in the tree of life, outside of some ‘oddball’ cases like making something out of a deactivated ERV.

6 responses to “It’s a Bird/Dinosaur!

  1. They end up forced to fit these things into one slot or another.

    Dinos having all those feathers… I want scales dangit! Now what am I stuck with? Crocodiles? Well crocs are cool.

    Fortunately, more recent artistic illustrations actually make feathered dinosaurs look cool.

  2. Hey, inheritance and polymorphism! I recognize those…

    The definition discussion reminds me of an article I read (which I can hunt down the source of if you’re interested) about how definitions should work… Essentially, define everything in existence in terms of really, really big tuples, and use those tuples to define where something belongs in a vast, many-dimensional Thingspace. A good definition should simply outline a cluster of instances of things in this Thingspace, while a bad one tends to twist and weave and make weird shapes if analyzed on even the relevant fields, or just cut off randomly in the middle of a cluster of stuff for no good reason. A word is just a shortcut for getting your brain looking at that section of Thingspace. This ends up having some interesting implications for definitions and, to give an example, why we might define a human as possessing 10 fingers and then calling someone a 9-fingered-human; instead of the definition saying he’s not human, the definition is just pointing you to the set of humans in Thingspace and then you can consider his deviation from the other parts of the “human” set separately.

    Just to note, obviously nobody actually attempts to map Thingspace somehow or something. It’s a tool for framing questions in your brain, not an actual well-defined method of working with stuff.

    The relevance would be that when you try to project it across history and categorize everything as either “bird” or “dinosaur”, you’d find that they’re sort of one big long cluster of Thingspace points, and any attempt to actually cleanly define a split would be artificial and just kind of look weird.

    …I swear, that was so much less rambly in my head.

    • Oh, and of course there would be more dinosaur-like things at one end, and more bird-like things at the other; it’s just finding a clean split that’s weird, not finding a difference between “bird” and “dinosaur” at all.

  3. There’s also the simple point that birds, or everything we are willing to call “bird”, do not all share one common non-bird ancestor. Birds stop being “birds” before the family tree meets up, it isn’t a “clean” tree like “mammal” is. Simply put, the evolution of feathers occurred much earlier, in the dinosaur lineages, as all these fossils show. The evolution of flight occurred separately multiple times among those feathered things, leading to different lines we would eventually group together as “birds”, but it is a group of similar traits, not a group of common decent (at least not without digging much further into the past).

    This is sure to trip up any creationist. They want birds to “evolve from” some specific animal, one that’s gone because it “became” the birds, because that’s a simpler idea to argue against (and also wrong). It just doesn’t work that way, it’s a lot more complicated than, say, apes and humans (am I the only one that’s perfectly content just calling the whole collection of monkeys, old world monkeys, apes, and humans, simply “monkeys”? I do anyway.)

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