It’s not a debate

This article is ridiculously biased. It’s about Louisiana adopting new biology textbooks that *gasp* fail to mention the debate regarding creationism/intelligent design and evolution.

Their main interviewee here is a professor of communication disorders. Not biology.

As soon as all of this school stuff dies down get prepared for the next bunch of awesome extinct animals.

 

 

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evolutionary inevitability and technological taxonomy

So I guess I’m taking requests now.

I was directed to this short edition of Radiolab by a friend of mine. She told me to write a blog post about it. I’d refer you to her Livejournal, but it’s, you know, friends only. Anyway, it’s a good discussion and is absolutely worth listening to.

The podcast is bringing up the fact that given a certain set of “prereqs,” most technological inventions are essentially inevitable. The part of the discussion that is the most interesting to me (and perhaps to you, if you’re reading this) is the analogies they make with biological evolution. They mention the fact that complex eyes have independently evolved multiple times in the history of life on earth and that this is just a byproduct of physics – light waves travel fast and this is probably the best way to gather pertinent information about the world. It should be noted that on our particular world the presence of eyes probably didn’t happen on a large scale until substantial predator/prey relationships began to evolve. So the prereqs for eyes are: a universe with physics similar to ours, and specific ecological relationships. Weirdly, this kind of teleologic evolution doesn’t bother me that much. Other kinds do. For instance, the speakers in this podcast sort of offhandedly mention a tendency towards increasing sentience. That might be where I draw the line, even though it is sort of hard to argue that mammals aren’t the smartest creatures to have yet evolved on earth.

This all reminds me of a semi-drunken argument I had a few years ago at a bar in rural Catalonia. I was working on a paleoarcheological dig and there were some pretty cool people there. Specifically, I was having an conversation with a British version of John Locke (from Lost, not from political philosophy 101) and a Deadhead from Massachusetts. Despite the stereotypes that I have assigned them, both of these guys are smart, educated guys who have read widely in evolutionary biology and paleontology. But they kept insisting that given a hypothetical that the Chicxulub impact didn’t happen and the dinosaurs did not go extinct, then some of the smarter dinosaurs like Troodon (the umlaut was dropped, right?) would have eventually evolved into some sort of Sauro sapiens.

WHY IS IT UPRIGHT? THE TROODON'S HANDS ARE ALREADY FREE!

Just think. If Russell had thought of this 5 years ago instead of 25, it would be covered in feathers.

I think this is total bullshit. I mean wasn’t it obvious that the whole dinosauoid thing was thought up by Dale Russell when he was super high? Human-like sentience seems like something that required a very particular set of conditions and sequence of events to happen. I’d even bet money that if we re-wound the video of evolution back to the chimp/human last common ancestor in the Miocene and hit play, we’d almost certainly NOT end up with modern humans some 5-6 million years later (objections made by arch-determinists notwithstanding).

The speakers in the podcast also mention Niles Eldredge (if you have a passing familiarity with evolutionary biology, you’ll remember him as the co-formulator of punctuated equilibrium, along with Stephen Jay Gould) and his work on trilobite systematics (that would be the study of the evolutionary relationships between trilobites). And how Eldredge apparently also collects cornets (like, brass instruments) and does cornet “systematics.”

ANYWAY. all of these biological analogies are in the service of making the argument that technology is not only a product of evolution, but possibly worthy of it’s own taxonomic kingdom. I don’t have a problem with this. I say lets do it. But if it’s going to get it’s own kingdom, let’s go all the way. Let’s devise a hierarchical classification system and make cladograms ‘n’ shit. And since we can start from scratch, lets NOT do the whole Linnaean thing. I’m actually sort of serious about this.

 

NOTE: here is a link to a paper Eldredge co-wrote about cultural evolution. Reading it now.

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Pterosaur takeoffs

This is totally awesome.

Also props to them for using Ceradactyl as an example though from what I understand we don’t actually have anything other than an incomplete skull for that one (though my pterosaur book is 20 years out of date). If I wasn’t doing paleoanthropology, I would want to do pterosaur paleontology.

The paper is here if you want to read it.

 

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bones in the brain

So it’s been a week. I’ve been pretty busy trying to get a thesis proposal done and I have lots of ideas for blog posts but little time to actually read a few papers and write something. This is why pop culture entries are a little easier. There was even a paper out a few days ago on differential brain development in humans and Neanderthals (check it out here) that I’ll eventually get around to talking about. But instead you’ll get this.

So a lot of this paleo/anatomy stuff is inspired by my comparative osteology class, where I come across an interesting anatomical feature and I want to know more about it. In this case, it’s the ossified tentorium cerebelli, which is generally only present in carnivores and dolphins (and weirdly, spider monkeys). Why? I dunno. And neither does anyone else according to a somewhat cursory use of GoogleScholar.

First off, the tentorium cerebelli is an extension of the dura mater (which is the outermost meningeal layer – that’s the stuff that covers and protects the brain) that separates the cerebrum and the cerebellum. These are two very different parts of the brain, with radically different textures and functions. Also,the tentorium is connected to the falx cerebrei, which is the little sheet of dura mater that separates the right and left hemispheres of the cerebrum. They make this interesting 3D structure in the cranial vault.

The tentorium and falx do not normally ossify, but enough clinical cases have been noted in humans for it to be a thing. It seems to happen especially in the eldery. This is not completely surprising – lots of shit that shouldn’t gets turned into bone as you get older.

But why is it consistently present in dolphins, carnivores, and spider monkeys? Again, no one is really sure. Just about the only thing we can say about it is that it is not developmentally homologous throughout these animals. In dolphins and spider monkeys, the bony tentorium and falx are not seen in immature individuals and only develop as the animal ages. By contrast, the bony tentorium and falx of carnivores are present even in the fetal stages of development. So, though they may seem like the same trait, they probably have drastically different causes. (if you wanna read the only helpful paper I could find on this, it’s here)

I’m not sure there’s really a whole lot else to say, partly because not a whole lot appears to have been written about it. What is it’s adaptive function? Does it have an adaptive function? Somebody‘s gotta be doing this shit. Right?

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TV, The Who, Nerdery

The few hours between getting home from middle and high school and my mom coming home from work were almost always the happiest of my day. It’s not that I hated school or my mom – on the contrary, both treated me pretty damn well. But it was a period of time where I could watch meaningless TV, play computer games or guitar, listen to music, whatever. As I got more involved with after school “activities,” this time because less frequent, but no less important.

So this scene from the Freaks and Geeks episode “Dead Dogs and Gym Teachers” really struck a chord with me. Not to mention it (and the whole episode) is scored with Who songs. My relationship with The Who is probably the longest and most durable of any band. They were the first rock band I ever really loved and provided a large portion of the soundtrack to my adolescence. As I’ve gotten older, they’ve stayed with me a little better than some of my other musical obsessions, primarily due to the quality of Pete Townsend’s songwriting (especially in the mid-sixties singles).

But this is probably the best scene in great show, telling you all you need to know about Bill Haverchuck without any dialogue. Mad props to the totally underrated Martin Starr (if you haven’t seen the show Party Down, you might want to get on that) for making Bill almost outlandishly dweeby, but completely believable. Nerdery is something most movies and television shows never seem to get right. But Bill feels right to me, and this scene was instrumental in making that happen.

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My evolutionary litmus test

Whenever I criticize a political candidate’s or other public figure’s lack of acceptance of evolution the refrain I often hear is, “Why does that matter? How does that impact their ability to make decisions regarding other issues that I actually care about?” This essentially translates to: as long as they’re making decisions that I agree with (and may even benefit from) in other areas, they’re free to believe whatever they want. I see where those people are coming from but I have to disagree – the moment a political candidate makes any positive remark concerning intelligent design, or saying that evolution is “only” a theory, they’ve lost me forever.

First of all, when it comes to worldly matters such as governance, I should hope that scientific reasoning based on material processes trumps metaphysics. That is almost a given, right? Can we all agree with that?

Evolution is a grand scientific theory in it’s purest form: it is a powerful explanatory hypothesis regarding how things on Earth came to be. It makes many predictions about things we cannot observe directly (and some we can observe directly). But it does so in a rational and falsifiable way. The particulars of the evolutionary hypothesis change all the time as new evidence comes to light. This, to me, is the great triumph of science: the constant reappraisal of a paradigm as facts emerge. This kind of pragmatism strikes me as a great way to govern.

To me it seems that evolution in particular (more than relativity or Newtonian mechanics) is the best indicator that a person can think rationally about a historical concept that cannot be directly observed. Obviously, we cannot directly observe that humans and chimpanzees shared a common ancestor ~6 million years ago. But a variety of evidence – morphological, paleontological, and molecular – points to that conclusion. It is this integration of fields that makes the study of evolution distinct from other sciences, as well as making it an appropriate analogy to the “real world” of politics. When making a large decision, a ruler will hopefully have input from a variety of disparate sources. It is the ruler’s job to integrate those into a coherent picture and make an appropriate decision.

Unlike other scientific paradigms, evolution does not require advanced math to truly understand it (though math certainly helps in the more reductionist descriptions). One cannot follow a pure mathematical argument and come to the conclusion that the present life on earth has arisen from previous (and different) biotas. Similarly, the grand theory  of evolution cannot be “proven” in a deductive Popperian sense – though all of it’s separate components have been deductively proven time and time again. A ruler generally does not have the luxury of making deductive inquiries and must rely on historical and inductive arguments to make decisions.

Obviously, this has all been prompted by this midterm election happening tomorrow, and the fairly large proportion of candidates that profess some sort of “doubt” regarding evolution and/or it’s place in the public school curriculum. This never ceases to impress me – I could understand it coming from candidates for state office, or possibly even the House of Representatives. But candidates for the Senate! Now, I’m not arguing that candidates who accept evolution are automatically better rulers or legislators than those who don’t – I’m simply saying that I think it reflects a way of thinking that I think is more conducive to governance than say, creationism.

ANYWAY, vote (if you must) for whoever the hell you want.

 

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postorbital ponderings part deux

So where was I? Ah, right. Mammals lost the postorbital bar early in their evolution but many taxa have secondarily evolved them again. What’s up with that?

I can't believe I watch SNL enough to think of this.

Any explanations regarding the reappearance of the PO bar will necessarily make an explicit functional hypotheses. Heesy (2005) cites three common ones and dismisses all but the last: that the bar is there to protect against trauma, that it reinforces the PO region against torsional loading due to mastication, and that it stiffens the PO region in mammals whose eyes have a divergent relationship with the temporal fossa (the space in mammals that houses jaw muscles). This is particularly important for mammals that need to be able to chew and see at the same time. Like, uh, primates. Or horses. Heesy’s 2005 study successfully correlated the presence of a PO bar with the degree of angular deviation between the plane of the orbit and the plane of the fossa. It is thought that when the angle is smaller, the more likely it is that the jaw muscles will deform the orbit if there is no bony support structure.

I buy it (but really, what do I know?). Yet I still wonder about some cool fossil animals with PO bars.

Like this guy

This is Janjucetus hunderi, a fossil baleen whale from the Oligocene with huge teeth (thanks to my advisor John Langdon for pointing it out). As you can see, he’s got a pretty big, obvious PO process, though Fitzgerald 2006 seems careful not to say it’s a PO bar. I presume that this is because the process doesn’t quite connect with the zygomatic process of the squamosal. In any case, it seems clear that things were headed in that direction. I’d really like to determine if the angle between the PO process and the temporal fossa is at all like the other mammals a la Heesy. The orbits do seem to be more facing more forwardly than in other whales, but that’s just me looking at the pictures in the publication. Though this guy probably not chewing his food with any great force, so that functional hypothesis might not work here.

If you’re interested Janjucetus you can check out its original description here. Or if you don’t feel like reading a paper you can read Carl Zimmer’s great summary here.

Fitzgerald, E.M.G. (2006) A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proc. R. Soc. B. 273: 2955-2963.

Heesy, C.P. (2005) Function of the Mammalian Postorbital Bar. Jour. Morph. 264: 363-380

Sidor, C.A. (2001) Simplification as a trend in synapsid cranial evolution. Evolution. 55(7): 1419-1442

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