Just what is a dinosaur anyway?
|Feathered dinosaur tail in amber, Xing et al., Figure 1|
As expected, the discovery last week of a feathered dinosaur tail elicited some interesting responses. Overall, the reactions from creationist ministries were pretty close to what I expected: "It's not a dinosaur; it's a bird." You can read Frank Sherwin's thoughts at ICR or David Menton's take at AIG, and if you're so inclined, there's another unsigned piece over at ENV. On the other hand, Marcus Ross wrote a really detailed discussion where he agreed with me that the tail is probably not a bird.
Frankly, I can understand the skepticism. After all, it is just a small segment of a tail. There isn't much there to make a positive identification from. We can't be absolutely certain it's a dinosaur, and we can't be absolutely certain that it's a bird. That's one of my complaints, too. Nearly every reaction I've read criticizes the press (especially National Geographic) for being so certain that it's a dinosaur, but some authors turn around and claim that it's "most likely" a bird. That's just false. If it is a bird, then it's unlike any bird we've ever seen. It possess characteristics that we've never seen in birds before. So it's not "most likely" a bird, nor does the "evidence support" the bird identification.
Other critics ask such questions as, "Why do evolutionists claim this bird tail is a dinosaur? Pride, grant money, reputation." First of all, that kind of rhetoric seems uncharitable. I do not want to judge other people's motives any more than I want other people to judge mine. Only God looks on the heart, and I'm not God. Just as importantly, the question doesn't really work the other way: Why do creationists say that it's a dinosaur tail? And why does Marcus Ross with his Ph.D. in Mesozoic vertebrate paleontology (the creationist who is closest to an expert on this subject) think it's not a bird? Maybe because the evidence shows that it's not really like any bird we know about!
I'll let more capable scientists (like Dr. Ross) work out the anatomical details. I've got something more annoying on my mind, and it's annoying because I still don't quite have a good answer to my own question. What exactly is a dinosaur? And for that matter, what is a bird?
Seems like a silly question, doesn't it? Any child can tell you what a bird is. It's an animal with a beak and feathers. Dinosaurs are big, extinct reptiles like Tyrannosaurus or Triceratops. Scientists could get even more detailed and talk about the hole in the acetabulum that makes T. rex and Triceratops both dinosaurs. That doesn't actually answer the question. Sure, I can see that certain characteristics can be used to define groups, but those characteristics don't actually tell me what the group is.
Let's relate this to a different question: What is human? That's a question I feel I have a better handle on. Humans descend from Adam and Eve, who were specially created by God in the Garden of Eden. Humans bear the image of God. Humans are eligible for redemption through Jesus Christ's death on the cross. Now you might say that these characteristics also do not tell us exactly what a human is, but there's a big difference here that I think is important. "Human" is a real category. There are things that are human, and there are things that are not human. There are no half-human things. When we argue about whether Homo naledi or Australopithecus sediba is human or not, the argument has value because there is a correct answer. God may be the only one who knows that correct answer for sure, but there is still a correct answer.
What about "dinosaurs" or "birds?" They're not species. Species are categories of organisms that have certain characteristics that biologists are familiar with. We know them when we see them (for the most part). It's true that biologists often argue about some species, but no one really doubts whether lions or grizzlies or killer whales are species. Birds consist of many species. So do dinosaurs.
Are they created kinds then? Our current idea about created kinds of terrestrial animals could put multiple species in a single created kind, all of which descended from an ancestral population created by God. Is that what birds are? I don't know any creationist (myself included) who would put all birds in a single created kind.
So what are these categories "dinosaur" and "bird?" They are groups of (many?) created kinds. So what exactly is that? I have no idea, and I honestly don't know exactly how to argue about their membership in any meaningful way. On the one hand, I can say with Dr. Ross that this tail in amber looks substantially different from any other bird that we currently know about. So that would seem to exclude it from birds as we know them. But what if it's a bird that's different from any bird we already know? I don't know how to rule that out, because I don't know exactly what a bird is. Honestly, I'm not sure "bird" is anything more than a shortcut for saying some vertebrates have feathers and beaks.
What we're trying to explore here is the larger pattern of created kinds. We can see that there is a pattern of similarity between created kinds. We talk about vertebrates and insects and trees and mushrooms, and we know that those categories include multiple created kinds. But what are these larger groups? I am certain that they are telling us something important about God's creation and that we need to pay close attention to them, even though I don't know exactly what to they are.
I am not convinced that these larger categories that contain multiple created kinds work in the same way as created kinds, where we could argue about whether this or that creature belongs to "bird" or "dinosaur." As I look at God's creation, I see many intermediate created kinds that seem to blend attributes of different large categories, creatures like the platypus (with it's fur and beak and egg-laying) or the velvet worm (with its legs like a caterpillar and segments like a worm). The larger pattern forms a much more complicated picture than just "this is a bird not a dinosaur." That's just hopelessly oversimplified.
Evolutionists reading this are probably pulling their hair out by now, thinking, "This idiot doesn't recognize evolution when he sees it!" They would say that the "intermediate created kinds" are actually intermediate forms on the great tree of life. The reason we find feathered dinosaurs is that the modern birds with their feathers evolved from dinosaurs. Given evolution, we should expect feathered dinosaurs!
Or should we? Evolution gives a decent retroactive explanation for feathered dinosaurs, but I'm not sure it predicts them in any meaningful way. For example, I could imagine that the first birds evolved as ground runners without any feathers at all. Only later did some "primitive birds" evolve feathers, from which all modern birds descended. Evolution theory alone appears to be entirely indifferent to whether there would be feathered dinosaurs. So it seems to me that neither evolution nor creation provides a necessary reason for feathered dinosaurs, but I would guess that creation has the potential to, inasmuch as creation biology theory is still very much in its infancy and has a lot of untapped creative potential.
This is all really interesting theory, and I'm glad I got it off my chest, but let's review some basics so we don't lose sight of the main story. The fossil in the picture above has attributes that we can observe directly. There isn't much left, but what we can see looks different from any bird that we know about (living or fossil) even though it does look like some dinosaurs that we know about. Whether or not we can define "dinosaur" is a really interesting problem, but we can still recognize that certain groups of created kinds have many traits in common and we use words like "dinosaur" to describe those groups. So we shouldn't avoid the weird reality that creatures that otherwise look like dinosaurs had feathers just because we don't accept that birds evolved from dinosaurs.
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