After I made my post last week about using the X-Men to teach students about how we define humans AS humans, I was talking with some geology friends and came up with another teaching tool from this story that I think could be really helpful. I think action figures can be used to help students understand the difference between a biological species and a fossil species.
In anthropology we have to talk about ‘species’ as both a living biological classification and as a fossil classification. And because we study human evolution, we, in fact, transition between the two. This can be really hard for students to grapple with. A biological species makes sense to them, because we can (usually) see members of the species mate and produce viable offspring. We can study their genetic makeup to see how much DNA they share in common, and which other species they share a lot of their DNA with as well. And a biological species is something most students have thought about before, and discussed in their high school classrooms.
Paleontological species are a whole other issue though. They are based primarily on morphology of skeletal features. Often these skeletons are incomplete. Sometimes there are not very many fossils of a particular species, so we have a hard time determining just how diverse that species is.
For example, if I see a male gorilla and a female gorilla, I can see quite clearly that we have two members of the same species, but they have great sexual dimorphism; males and females LOOK very different. Their skulls make these differences even more obvious. Human males and females are different as well, but not nearly so much so as gorillas. And if you think about the diversity WITHIN one sex of our species (Yao Ming vs. David Spade, for example), you can imagine a lot of variability in those skeletons. Yao Ming is tall and he works out a lot. He will have larger bones with larger muscle attachments. Davis Spade is portable.
So imagine you find a fossil hominid. You only have 25% of the skeleton. Then you find another skeleton at a nearby locale. You have 25% of that fossil also, but it’s not necessarily the same bone fragments. How do you tell if they are members of the same species? Or members of closely related species? Maybe they look very different, but in fact represent one species with a lot of variability; a Yao and a David? Now lets say you find another fossil hominid. It is from one million years earlier. It might look different, but again, this could be variability within one species. Just think about how different Americans look today from our ancestors less than 200 years ago. We are certainly taller. Franz Boas argued that children of immigrants were physically very different from their parents. While Lee Jantz later critiqued this study, he just came out with his OWN study arguing that EuroAmerican skulls have been changing shape over the last 200 years. (I’ve got some questions about HIS study but I need to read it, and not the Internet News articles, before I get into that). If you are interested in all the back and forth, read Jason Antrosio’s post about human skulls.
Now imagine that part of your job is to decide if these fossils you’ve found represent one or several species, and if they belong to new species or ones that have been previously defined. This is NOT easy. And no matter how you define it, you will probably find someone who disagrees with your choice.
Some paleontologists are lumpers – they see a lot of this as variability within species and tend to prefer a smaller family tree. Some paleontologists are spliters – they see a benefit in having many different species, in part, this can help us recognize some of the variability that is present, variability that they think is significant.
These are important questions. And as we improve our ability to collect DNA out of some recent fossils, we’re getting a better understanding of what the genetic variability of some recent hominids was like. We now know that European and Asian people have some Neanderthal DNA in their genome. And people in Papua New Guinea share some DNA with the Denisovans. So there was some ‘cross-breeding’ that happened. But does this mean that we should not call Neanderthals a separate species? Well it depends in part on what you think the purpose of defining a species is. And it depends on whether you think Neanderthals and Modern Humans mated together regularly and by choice. Just because you CAN produce viable offspring doesn’t mean you want to. And sometimes this opt-out program is a characteristic that biologists use to define different species (monkeys that live in the same forests and are geneticallly capable of producing offspring, but live in different levels of the forest and don’t mate, for example).
The point is – it is HARD for a student to understand that when a paleontologist says ‘species’ it might not be exactly the same thing as a biological species. Because the student thinks s/he already knows what a species is. And when I try to explain that the characteristics we use to differentiate fossil species from one another are salient to us as we look at their skulls, but may have had no relevance to those living creatures, they have a tough time wrapping their brains around that. They want facts. They want boundaries. They want to be able to memorize it and move on.
And this is where I think those X-men could come in really handy.
In case you forgot (or didn’t read the other post), some attorneys for Marvel successfully won cases against the US Government, arguing that all Marvel Action Figures represent toys, not dolls. This means they are not ‘representing ONLY human beings’ (and therefore have 1/2 the tax to import). Now we all know the X-Men ARE in fact human beings. So is the hulk, he has just been irradiated. So are pretty much all of the Marvel Superheros and Villans (at least until recently).
But if you look at the Hulk’s skull morphology, it looks VERY different from other Anatomically Modern Humans.
I. LOVE. That. Skull. But moving on…
When the attorneys for Marvel made their arguments, they didn’t talk about comics, or movies or TV shows. They talked about morphology and the action figures themselves. They argued that beast is not human because he has blue skin, and humans do not have blue skin. True. But this says nothing of beast’s parentage, his intellectual abilities, his behaviors or his genetic makeup. By using only the action figure, the attorneys have a limited data set that is missing a lot of important information about the character. Yes Wolverine has claws. But you can’t tell they are implants from the action figure.
And this is why I think the action figures could be a great teaching tool for explaining the difference between a fossil species and a biological species. If we watch an X-Men video, we can discover much more about the way these creatures engaged and interacted, and what their behavior is like. But if I hand you Beast and Wolverine action figures and ask you if they are the same species, you may very well say no. Because based on the data in front of you, you have to make an educated guess. Over time I could hand you more X-Men. I could tell you several of them were found together in Professor Charles Xavier’s school. That would give you a nice range of morphology to compare, like the ‘First Family’ Don Johanson discovered just a year after he found Lucy That is new data which might change how you interpret your figurines.
But my students will know, having seen X-Men videos, that these are all humans with some sort of mutation. In the same way that a woman with red hair has some different alleles than a woman with brown hair. So perhaps, by forcing a student to limit his or her interpretations to action figures, the student will see how difficult this is, and why I don’t give them straightforward answers about the hominid family tree.
I should say, for many fossil species we DO have a lot of representative fossils. But we are exploring new sites and discovering new species all the time as well, and each time you start, you have limited data. For some species we start with just a tooth! It turns out primate teeth are extremely diagnostic, but that is some fine detective work you have to do there.
What do you think? Will this example work? Anyone have Marvel action figures they want to loan me this fall so I can try this out (or can you think of a granting agency that will cover their purchase!?)
I could continue this on and make the Hulk’s wife Caiera a Neanderthal, and the Hulk a Modern Human, and their son Skarr could be the Child of Lagar Velho fossil. But I think that might be jumping the Megalodon. Yeah, I just typed that.