Therizinosaur Pelves are Wierd

Therizinosaurs are, in my opinion, the strangest dinosaurs. I covered the group in some detail back on the original blog, and Brian did a wonderful job of summarizing the group and discussing its newest member. I've been thinking about these hulking beasts for quite some time, specifically, how they got around. You see a lot of illustrations of derived therizinosaurs standing almost-but-not-quite upright, the majority of their substantial weight far in front of their legs. It looks almost comical--it's as if the animal is trying very hard to avoid falling flat on its face. I have also seen the occassional restoration (Luis Rey comes to mind) of a derived therizinosaur standing in usual theropod posture, horizontal back, arms folded to the side. This posture is ridiculous for two reasons. First, advanced therizinosaurs like Erlikosaurus and Therizinosaurus had arms which functioned more like ornithomimosaur arms than dromaeosaur arms. A relatively new study by Lindsay Zanno suggests that therizinosaurs had an increased dorsal reach and wrist flexibility, as well as a reduction in individual finger length. The arms also became robust the muscular. The claws, which weren't so much sickle-shaped as weakly curved, are also analogous to ornithomimosaur claws, although obviously much longer.

The second reason is that, due to their expansive guts, enlarged arms, and short tails (which, in Beipiaosaurus at least, ended in a pygostyle), a therizinosaur's center of gravity would have been closer to the pectoral girdle, rather than the pelvis. In most theropods, the bipedal posture works thanks to the long, heavy tail, and short body which lacks an herbivore's stomach. The center of gravity of, say, Allosaurus, is just in front of the hips. The reason a running allosaur does not fall onto its face is because the large tail counterbalances the body.

Sadly, this is not the case in therizinosaurs. We know that these Cretaceous giants had enormous cuts for several reasons. First, their pubes point strongly backwards, and the pelvis itself is ridiculously wide. While the pubes and ischia meet at their distal ends, there is a significant space between the left and right halves. This condition is seen in other herbivorous dinosaurs. Also, in a feature unique among all dinosaurs, therizinosaurs re-evolved pedal digit I to not only touch the ground, but bear weight. In other theropods, pedal digit I is a vestigal organ, which a splint-like metatarsal that does not even reach the ankle. The vestigal toe itself is something of a dewclaw. In birds, this toe became reversed, moved down on the foot, and became the seminal "reversed hallux." Therizinosaurs enlarged the 1st toe, regrew their metatarsal, and, soon after Nothronychus, became functionally four-toed. This is obviously an adaptation for carrying weight.


While I'd like to see his reference material, Jaime Headden has put together a wonderful visual summary of known therizinosaurs (minus Falcarius and Suzhousaurus). Of the known genera, Alxasaurus, Segnosaurus,a nd Neimongosaurus are the best-represented. The best skull material is from Erlikosaurus (and Falcarius), and Nanshiungosaurus. But what really fascinates me about the therizinosaurs, and this relates directly to their posture, is their extremely strange pelvis. Falcarius, Beipiaosaurus, and Alxasaurus are the most primitive members of the group, so their pelves are a bit closer to the ancestral theropod condition. Segnosaurus and Nanshiungosaurus preserve the best pelves, and here's a better look:
A and B detail the pelvis of Segnosaurus, a reasonably derived therizinosaur. What blows my mind is not the width of the pelvis or the retroversion of the pubis, but the flared iliac blades! Those things jut outward at, according to The Dinosauria, 2nd Ed., a 90-degree angle to the line of the sacrum. How, exactly, did the thigh muscles attach to that ilium? It boggles the mind, and I never know how to restore therizinosaur legs when I attempt to draw the beasts. Even stranger, though, is Nanshiungosaurus, whose pelvis looks reversed and broken, somehow.

Anyway, I hope I've shown that a strictly bipedal posture seems...impractical for advanced therizinosaurs. A quadrapedal posture seems more likely, but again, we have a problem. First, complete arms from derived therizinosaurs are virtually unknown. Segnosaurus and Erliansaurus are perhaps the best examples outside of Therizinosaurus. See, what we're trying to do is see the arm vs. leg proportion, which is why Therizinosaurus' complete arms are unhelpful--its legs are pretty much unknown. Beipaiosaurus actually has incredibly long arms, but it's also fairly primitive, so long arms could have simply been inhereted from its maniraptoran ancestry (although Falcarius' arms aren't ridiculously long).

What I'm getting at is that perhaps, like chalicotheres, therizinosaurs walked on their knuckles. I know that sounds crazy at first, but there are some surprising similarities. First, both advanced therizinosaurs (if Therizinosaurus is any guide) and chalicotheres had fairly long metacarpals followed by short, stubby, and robust phalanges. In chalicotheres, only two fingers were weight-bearing, and were the same length. Although it can't be known for sure yet (incomplete material), it looks like the 2nd and 3rd fingers of derived therizinosaurs were approximately the same length. Both animals had adaptations for reaching and wrist-twisting to reach vegetation and manipulate branches. Therizinosaurs also converged on chalicotheres (or, perhaps the other way around) in having large, robust ischia to support the weight of the body in a sitting position.

However, chalicotheres a significant difference over therizinosaurs: the legs are incredible short, while the arms are incredibly long. In therizinosaurs, as far as I can tell, the legs are longer than the arms. In some cases, the arms and legs may have been subequal in length. However, therizinosaurs certainly did not even begin to approach the proportions set by chalicotheres. But there is another knuckle-walking mammal that had limb proportions similar to those of therizinosaurs: ground sloths. In fact, ground sloths may be a more fitting analogue. Ground sloths had flaring iliac blades and enormous ischia for sitting, after all. They also had long, uncurved claws for scratching and pulling on vegetation.



But ground sloths, too, have their differences. For one thing, they are incredibly robust in all aspects of the skeleton. The limb proportions are a bit more toward the therizinosaur side of the equasion, but the forelimbs are still a bit longer than the hindlimbs. Like modern sloths, though (and chalicotheres!), ground sloths would have been knuckle-walkers, with the ouside of the hand facing outward. This is unlike the knuckle-walking of great apes, in which the front of the hand faces forward. Given the maniraptoran nature of the therizinosaur paw, the same motion would have been true of those Cretaceous beasties. The hands were probably unable to swivel into a gorilla-like posture, and placing the palm flat on the ground is completely out of the question, given the structure of the wrist as well as the sheer weight of the animal (I can just hear those bones snapping!).


I've been trying for days to draw a knuckle-walking therizinosaur, but the whole pelvis area is killing me. If somebody can tell me how the muscles of the thigh attach to a flared ilium, I would appreciate it. At any rate, this is an idea that I've been thinking about continuously for a few weeks now. I should mention that Russel & Russell thought up the chalicothere angle in 1993, a fact I learned only after beginning to seriously research my knuckle-walking hypothesis. There's nothing more disheartening than learning that the idea you thought was so new was already proposed almost fifteen years ago. If anyone has that paper, by the way, feel free to send it my way! :-) The full citation is:

Russell & Russell (1993). Mammal-dinosaur convergence. Evolutionary convergence between a mammalian and dinosaurian clawed herbivore. National Geographic Research (9): 70-79.

In the meantime, I'll keep working on my knuckle-walking therizinosaur.

Pictures of Chalicotherium and Megatherium taken from Wikipedia. Jaime Headden's therizinosaur panoply taken from...the internet. Therizinosaur pelvis diagram taken from The Dinosauria, 2nd Ed.

The Book of Skulls

As many of you probably know (if you're a dedicated WPF reader), I've been brainstorming a book for the past 18-odd months. I really want it to be about dinosaurs, and I want it to show off my artistic abilities as well as my writing skulls. This last summer, I began to take that hypothetical book in a direction which I'm still fascinated with today: The Book of Skulls. The book would basically be full of dinosaur skulls (and possibly other archosaur skulls for comparison), both colored and B&W (facing pages). What excited me the most, though, is the color plan: each bone would be the same color in each skull. That is, the maxilla would be orange, no matter what animal is being illustrated. That way, readers could see how the same bone changes over time and because of dietary needs. The maxilla of Eoraptor (above) is a lot different than that of Lesothosaurus or Camarasaurus.
I have already completed over a dozen skulls, some in need of color, and I plan on representing every major dinosaur group. Some skulls are much more difficult than others. Ankylosaurs, for example, have skulls as wide (if not wider) as they are long, making a profile view of Euplocephalus something of a puzzle. Other skulls are known from fragmentary remains. When I drew Silesaurus' skull, I was having trouble deciding how to portray missing bones. My solution was to keep the missing sections white, while coloring in the known portions. In doing so, I realized just how little was known of Silesaurus' skull, although the outline is clearly there.


Other animals were a challenge because so many restorations exist for them. Archaeopteryx proved irritating because almost every paper I have, and every book that describes it, features an illustration by a different artist or author. In the end, I used Greg Paul, but simplified the texturing so that the colors would better stand out. Interior skulls bones, where known, were once colored dark blue, but I eventually settled on light gray, as dark blue took the focus away from the exterior bones, which are my focus.

A good majority of my restorations have been based on three main sources: The Dinosauria, 2nd Edition, Dinosaurs of the Air, and Predatory Dinosaurs of the World. I have also used, whenever possible, the actual descriptions (or updated redescriptions) of animals in question. Amurosaurus (above), Monolophosaurus, Nemegtosaurus, and Silesaurus, among others, got the "straight from the description" treatment. I haven't done any dromaeosaurs yet, but I Velociraptor will be based on my own skull cast, and Dromaeosaurus will come from Currie's most recent reappraisal. By the way, check out Amurosaurus up there. How do they know it had a crest like that, if all they found of a crest was that tiny piece of prefrontal? I found a lot of that as I was restoring skulls. That is, conjecture of overall skull shape, which bothered me. I've blogged before (over at the original WPF) about how I greatly dislike restoring animals known from shabby remains. The example I used back then was Masiakosaurus, who is still no better known, yet there it is, on a poster I have. The thing could've had crests, horns, etc. What did its upper jaw do to cope with the strange mandible? We don't know!
I also just learned a lot about cranial bones while I was engorged by this project. I learned, for example, that Guanlong (above) actually has a lot in common with Monolophosaurus (below), and I like the idea that the two may be conspecifics, the former being a juvenile of the latter. I've talked about this before, and Darren told me a little bit about it in the comments, but I'm still fuzzy on the details. The two skulls look surprisingly similar.

Now, I should mention that all of these skulls, as well as the ones I'm not posting here (there are way too many) are all in beta form. The color scheme is far from finalized, and I'm a bit shakey on some of the exact bone colors. Guanlong's formal description is where I got its skull, but the delineations between bones in the accompanying illustration were far from precise.

Anyway, let me know what you think of this idea, folks. I think this book would make for an interesting reference text, or just a fun dinosaur book. Each skull would have a brief explaination of the animal portrayed as well as specific comments relating to specialties of the skull's construction. And if anyone has a better Guanlong illustration, please send it to me!

I-Can't-Pronounce-That-osaurus

Yeah, yeah, I'm the late bloomer today. Even the freaking Anchorage Daily News sniffed out the press release before I got a chance to blog on this find. And then Neil and Will post on the topic before me! Ah, I'm just getting slow in my old age. My quarter-century birthday IS around the corner, after all. I would like to think, though, that my post has more interesting pictures. :-)

Yes, ladies and gentlemen, they've found a new uber-sauropod in Patagonia, where previous record-breakers, Argentinosaurus and Puertasaurus, were discovered. The new beastie, who is unfortunately named Futalognkosaurus dukei, is known from (apparently) 70% of its skeleton, making it the best-known Gondwana uber-sauropod. It is a fairly primitive member of the Titanosauria according to the cladistic analysis run by the authors of its description (link at the end of this post). The 70% includes the entire cervical and dorsal series, sacrals, pelvis, ribs, and one caudal vertebrae. The limbs and skull are, sadly, MIA. The authors are estimating the giant's total length at around 32 and 34 meters, which works out to around 105 feet long. Not the longest dinosaur ever, but given its relationship to Puertasaurus and Argentinosaurus, it is among the most massive.

As awesome as mega-sauropods are, the real excitement is that the team discovered an entire ecosytem in Neuquen, including some really exciting new finds. The picture above was scanned directly from the description, and they are: (a) Articulated vertebral column of Futalognkosaurus; (b) tooth of a dromaeosaur; (c) tooth of a carcharodontosaur; (d) tooth of a mesoeucrocodylian; (e) manus of Megaraptor; (f) pubis of Unenlagia paynemili; (g) femur of an iguanodontid; (h) part of an azhdarchoid pterosaur ulna; (i) fish; (j) angiosperm leaves; (k) plant stem; (l) lower jaw of a new notosuchid crocodylomorph; (m) skull of a new maniraptoran; (n) lower jaw of a new iguanodontid.

That's a lot of new stuff! Of note is the manus of Megaraptor, whose true phylogenetic affiliations have been unsteady for years. Based on the new material, Megaraptor is shown to be a basal tetanurine theropod that developed a hypertrophied thumb claw independantly of Laurasian spinosaurs. What it looked like, though, is anyone's guess. The Unenlagia pubis is hypothesized to be a new species, apparently more gracile than the old one. It's unusual to see so much iguanodontid material in Gondwana, and kills the idea that sauropods persisted down there because there was no competition from ornithopods. Crocodylians both marine and terrestrial were in Neuquen, which is really no surprise. That "maniraptoran" skull looks a lot like a dromaeosaur, and if that maxilla looks a lot like a dromaeosaur's. Could it be (gasp) Unenlagia? Same locality, same deposit. I would not be surprised, considering that Unenlagia is largely considered to be an unenlagiine dromaeosaur.

I await more publications on some of these fossils, especially the iguanodont material, new maniraptoran skull, and Megaraptor paw. Oh, and Futalognkosaurus ain't bad, either.

Calvo, J. O., Porfiri, J. D., Gonzalez-Riga, B. J. & Kellner, A. W.A. (2007). A new Cretaceous terrestrial ecosystem from Gondwana with the description of a new sauropod dinosaur. Anais da Academia Brasileira de Ciencias 79(3): 529-541.

P.S. Remember when I went on that big rant about how I hate it when people name animals after place names? Like Albertaceratops? Well, Futalognkosaurus is actually named after the corporation who sponsored the dig, Duke Energy. Hence, F. dukei. I'm not sure how I feel about this quite yet. I'm a bit leery, though, and we'll have to see how far this is taken. As Neil points out, F. dukei is not the first dinosaur to be named after a backer with deep pockets, and the practice does not seem to be widespread. But it does seem lazy, doesn't it?

Teaser

I know I promised a McLarge-Huge post about feathered dinosaurs for the Boneyard, but in brainstorming that post, I stumbled upon a more innovative topic. It's actually something that's been on my mind for a long time, but until very recently, I hadn't really thought it all the way through. But sometimes lightning just goes off in your head and you think: "Hey, I've got it!" And so I have. So after I complete a series of illustrations to see if my idea is even possible, I shall post on my mysterious topic.

But I can't just you all hanging, can I? I'll post a little teaser picture to get your blood flowing. Scott, you might know what I'm thinking here, but don't ruin the surprise just yet...

Tyrannosaurus rex has three fingers?!

Kudos to Scott Elyard to pointing this one out to me. As he notes on his website, the implications for paleo-artists like him and I are fairly obvious.

http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_132345.htm

Now, a few questions immediately come to mind.
1) Why does the third finger never fossilize?
2) Does this mean that other tyrannosaurs, like Albertosaurus and Daspletosaurus have three fingers, too?
3) What was the construction of this third finger like? Would it have been useful?
4) Would the third finger have been visible outsid the skin? Did it have a claw?

Oh, my head is swimming with conjectures now.

Also, congratulations to Brian Switek of Laelaps fame, on his move to that most esteemed of science blogging sites, ScienceBlogs. I have updated the blogroll, so upon clicking "Laelaps" on the right, you will be taken to his new site. On his recommendation, I shall continue posting well-written pieces on paleo and continue submitting my blog to ScienceBlogs in hopes of someday joining him!

Apologies, and a random thought

I'm sorry for the spacing issues in that big ol' evolution post. I tried five different times to make it all work, but it always ends up being morphed by eBlogger when I hit "Publish Post." I wish those ScienceBlogs people would get back to me. It's been two weeks, already! Even if they said "Sorry, no," at least I'd stop wondering about it!

Also, the cubicle I sit in is right next to a woman who speaks fluent Russian, and spends a good portion of the day speaking--in Russian--to other people, who I'm assuming are Russian. And I've determined, after three weeks at this job, that Russian is a harsh, ugly language that makes my ears bleed. No offense to any Russian readers I might have, of course. Now, the history and origins of Russia's mother tongue are fascinating, but the language itself is a slow burn. Perhaps that's only because I'm forced to listen to it for so many hours at a time.

Evolution for Dummies

This post shall serve as a crash course in evolutionary theory. Since so many people don't seem to (or don't want to) understand evolution, I figured it was time for a refresher. Many of these sections will eventually become part of a lecture I hope to start giving at the Alaska Museum of Natural History, where the turnout is usually terrible, but people actually come to learn, not criticize (what a novel concept!). The picture above is from Bininda-Emonds, et al. (2006) paper about the delayed rise of present-day mammals, and it's a darn good visual aid. While I've never really liked circular phylogeny trees, this one works pretty well thanks to its strategic use of color. If I'm not clarifying anything, let me know, and I'll work to improve it. My goal is to have people walk away with a full (if simplified) understanding of the evolutionary process, some easy examples showing why it works, and a greater appreciation for the science behind it. Now then, without further ado:

Change is Good

Evolution is not a difficult concept. In its simplest terms, evolution is the survival of those best suited for their environments. You may have heard it referred to as "survival of the fittest," but the word "fittest" is a bit misleading. "Fit," in this context refers to an organism's ability to survive in its environment, find food, and breed. In the end, Mother Nature is the ultimate judge and jury for any given species, demanding that we change or die along with the environment that spawned us. Put a polar bear in the savannah and it will quickly die. Put a lion in the Arctic and it will quickly freeze. Each animal on the planet is superbly adapted to deal with the challenges faced by its surroundings. In short, the environment shapes the flora and fauna that live in it.
The first thing I should make clear is that evolutionary theory is not concerned with how life arose. Whether the first sparks of life appeared in deep sea vents, on Mars, in lava beds, or on the surface of cave pools, that is not what's important. Ultimately, evolutionary theory seeks only to explain the processes by which life took off from that point. If you want an answer to how life arose, you should seek out a biochemist, astronomer, or, perhaps, religion. What I can tell you, with some certainty, is that life did not come from rocks. How organic life can be connected to sedimentary processes, I have yet to discover, and it is not a theory that anybody in the scientific community is suggesting. Yet from the time life first appeared on our little blue planet, almost 4 billion years ago, that life has been changing. If life had not changed and adapted to the changing environmental conditions facing it at every turn, we would not be here today.

Imagine that you are a tree shrew. A tiny, seemingly insignificant rodent that makes its living mindlessly running from tree to tree trying to find food and avoid being eaten by a bird. Your brothers and sisters are in the exact same predicament, of course, but you are special somehow. Your first finger is in a kind of reversed position. This means absolutely nothing to you, of course. Rather than study the construction of your palm, you'd rather run from that big shadow that just passed overhead. There are bugs that need to be eaten. And yet, you find yourself able to climb the tree faster and more adeptly than your cousins. You can cling to branches that your siblings would fall from. You agility in the canopy has ensured you an almost limitless foraging ground that is virtually unreachable by your family below. When it is time to breed, you find a willing little female, and in time, she produces a large litter. Some of these babies have their father's bizarre, yet somehow improved, thumb.

The babies grow up, doing basically what their parents did, and they have babies. The wierd thumb gene is passed on again, and the number of wierd-thumbed individuals increases with each passing generation. The shrews with wierd thumbs increasingly find themselves in each other's company. After all, only they can reach the upper levels of the trees, and this is an advantage that they take advantage of. At some point, a male and a female wierd-thumbed tree shrew mate, and the vast majority of their pups also have wierd thumbs. Eventually, two distinct populations of tree shrews become visible: The "original" crop stays on the tree trunks and lower branches, while a new batch can be seen leaping and cavorting around the canopy.
Ladies and gentlemen, that is how the process works. It could not be simpler. In fact, that example was perhaps too simple. Let me give you another one, that may strike a bit closer to home.

Upright? Alright!

Now imagine that you are a chimpanzee who lives in the jungle. You and your family have lived in the jungle for generations, of course, and you have never known a better life. Your family is a member of a large troops of chimps, and you notice that one of the younger males has a strange posture. He habitually walks upright, moreso than his siblings or parents. He has an awkward bow-legged gait about him, but otherwise seems quite comfortable wandering on two legs. Around the same time, you begin to notice that the boarders of your jungle turf are starting to close in on you. The weather has been terribly hot the past few years, and drier, too. Looking out beyond the boarders of the jungle reveals a frightening new landscape, alien to you and your family: grass. Nothing but tall, tan grass. The scorching sun beckons overhead, but you do not dare go out into that scary place. From your perch among the trees, you notice a host of huge creatures out there. Big elephant-like monsters and something that looks like a leopard, except larger, and with bigger teeth. Much bigger.

When on the ground, you cannot see over the top of the grass, and yet your boarders are becoming smaller by the day, it seems. From the treetops, you can see the encroaching grasslands impede upon other sections of the jungle, as if the tan blades are intent on overtaking the entire region. That strange chimp, however, wanders in and out of the grass with some regularity, often returning with strange vegetables and strange animals he killed. You realize that he can see over the grass, at least when walking on two legs, and has found a bounty of unrealized foodstuff. Other members of your troop often sometimes leave the jungle to try and replicate his results, but they do not often return.
After many years, the male becomes the leader of the troops, winning favor from all of the females with his bounty of food. His children also walk upright, and they watch their father take trips into the mysterious grasslands. They eventually follow behind him, where they meet other chimps from other parts of the sparce jungle regions who have the same adaptations as they do, both male and female. The cruel Earth punishes the members of his family who are unable or unwilling to keep up or watch the horizen, as saber-tooth cats and giant elephants brutally slay the lazy or foolish. By their loss, the overall upright chimp gene pool is strengthened, and eventually a new population of savannah chimps emerges. Like the tree shrews, two chimp populations are now apparent: the old jungle-dwellers and the new grassland chimps.

So it bothers me when people ask, "If humans evolved from chimps, why are there still chimps?" This attitude demonstrates a basic lack of knowledge regarding taxonomy and population dymanics. Just the other day, somebody (I forget who) asked me, "How did dinosaurs evolve into birds? Triceratops doesn't look anything like a bird."

Non-Avian Ceratopsians

The new always branches off from the old. The new never completely replaces the old. In the tree shrew example, as well as the chimp one, notice that the "new" species comes from the original stock, and only a small portion of the original stock. Not every chimp in the world suddenly turned into Australopithicus. Rather, in a single place in Africa, among a single troop of chimpanzees, a few individuals began exploring the grasslands. The other 99% of the chimps stayed in the jungles, content to keep doing what they'd been doing. In the Triceratops question, realize that saying "dinosaur" is like saying "placental mammals." There are a lot of dinosaurs, and only one twig (Paraves) of one branch (Maniraptora) of one stem (Theropoda) of the entire Dinosauria figured out how to fly.

Not all dinosaurs evolved into birds. Only paravians did. Not all chimpanzees evolved into hominids. It was probably an isolated event among a single population. But in all cases, the old group does not simply disappear--they keep doing what they always did.

So in this sense, every animal (and plant) on Earth is both a transitional form and a terminal taxon. Every kind of living creature comes from a pre-existing kind of living creature, yet the old will always remain, and is specially adapted to its environment. Every animal has the potential to produce a new species, yet every animal is tied to its environment in its own way.
Notice that, in the chimpanzee example, the upright chimps who begin exploring the grasslands meet others like them. I say this to illustrate another often-overlooked facet of evolutionary theory: mutation rates. The old Darwinian model suggested that mutation just happens over time, and until those mutations occur, the genetic pool is stable. That is simply not the case. When Eldridge and Gould were coming up with punctutated equilibrium, and then genetics came to the forefront of evolutionary research, scientists quickly realized that genetic mutations are constant among populations. I'll give you an example:

I have Cystic Fibrosis (no, really). I am one of thousands of people with CF, yet CF is most prevalent among those of European decent. Why? Because CF protects against cholera, and cholera outbreaks were fairly common in medieval Europe. Now, you don't actually have to have CF to be immune to the drying effects of cholera. Rather, you need only have a specific point mutation of the CFTR gene, which causes your cells to retain fluid (malfunctioning chloride channels). CF is the result of two people with CFTR gene mutations getting together and having a kid, at which point there is a 25% chance (the CFTR gene is a recessive mutation) that kid will get BOTH faulty copies of the CFTR gene, one copy from dad, and one from mom.
Now, when cholera was blowing through medieval Europe, people were dropping like flies in the streets (or, you know, in their homes). The CFTR mutation was not widespread by familial ties alone, rather it sprang up independantly in multiple places and families around the continent. Mutation occurs at a constant rate in a population, and certain mutations are, supposedly, always apparent in some percentage. The CFTR mutation remained hidden, however, because it gave its owner no real benefit...until cholera started sweeping the land. Only then, when the environment significantly changed, did the CFTR carriers suddenly have an advantage.

So when the grass started overtaking the jungle, the chimps who walked a bit upright would have suddenly had an advantage over their peers that was not apparent before. Supposedly, there are always a very small percentage of chimps in the world with a slightly upright posture. Why don't they become australopithicines? Because the environment does not demand it. Until the environmental conditions of the Miocene era repeat themselves, the slightly upright chimps have no visible advantage over their peers. Just like on Heroes, there are mutations even among our own species, but those traits are not advantageous until the environment justifies their presence.

Another assumption that always bothers me is that old Lamarcian notion that the giraffe woke up one morning and decided it was going to evolve a longer neck. That's not how it works. No animal pines to be another animal. But when the mutations we've discussed above allow an animal to take advantage of resources its peers are unable to, then its unique mutation will be passed around, and the mutation will spread. The ancestor of giraffes did not want to eat those succulent greens, but one day there was a giraffoid born with longer legs than its brothers and sister. Its feeding range was higher, and it was able to snack on a bunch of food that its siblings and family were not. The giraffoid wasn't aware of this change--it was just doing what came natural, as the phrase may be.

Lance Armstrong was born with an abnormally large heart, which I'm sure conferred upon him some measure of cycling success (not that hard work, intense training, and sheer manliness didn't help). If Lance Armstrong lived in a more primitive time, where aerobic endurance actually meant something, he would probably outrun other members of his tribe, who would have been eaten by wolves. Thus, he would've gotten first choice when it came time for baby-makin'. And that big heart would have been passed on to some of his kids.

So a Smilodon and a Thylacoleo Walk Into a Bar...

What about convergent evolution? Convergent evolution is where two unrelated animals develop the same trait to deal with similar environmental conditions. A great example of this is Effigia, a small crocodilian that developed a toothless beak, bipedal posture, and a handful of other advanced dinosaurian features independantly of dinosaurs. Creationists would say "It's just a dinosaur, see?" But it's not. It's an example of convergence, and convergence is one of the more difficul things to understand about evolutionary theory.

One could even argue, based on where it was found and when it lived (and who its neighbors were), that Effigia is a dinosaur-mimic. We see mimics all the time in nature: Caterpillars that mimic snake heads, snapping turtle tongues that mimics earthworms, butterfly wings that mimics eyes, insects that mimics plants. When it's breezy outside, my pet chameleon sucks his gut in, stands on his back legs, and wobbles back and forth, trying desperately to look like a leaf (I'm not sure who he's trying to fool)! Perhaps Effigia's ancestors were being gobbled up by Coelophysis, but the freaks who were wandering around on two legs were fooling their attackers into thinking the little Effigias were baby theropods. You never know. Maybe Effigia's ancestors were finding food or escaping predation easier on two legs.

Here's an easy example of convergence: sharks, dolphins, and ichthyosaurs. They all have the same general body plan: dorsal fin, large pectoral fins, fluked tail, big eyes, torpedo-shaped body. It's tough to say that sharks and dolphins are both "just sharks" or "just dolphins." The two are clearly different. Likewise, ichthyosaurs seem to be related to lizards, so despite their preference for live birth, ichthyosaurs are clearly reptiles. The trick is that an oceanic lifestyle, especially if you're a hunter, requires a certain bauplan. The slick, torpedo shape is streamlined and is resistant to drag. This adaptation is easy to envision--ancient sharks, dolphins, and ichthyosaurs with more streamlined shapes were able to move better in the murky depths, thus ensuring a plentiful bounty of food. In all three animals, a tail fluke developed as the bony part of the tail bent sharply downward at its end, and a cartiligenous spur emerged at the bend, supporting a fleshy fin.

This allowed each animal to propel itself through the water--certainly an important adaptation. It should be noted that a tail fluke is not the only way to go. Mosasaurs, which propelled themselves primarily with their tails, adopted a flat, crocodilian tail surrounded by a fleshy "fin," enlarging the tail's surface area. Take a look at a sea snake's tail for a modern example of a mosasaur tail. Anyway, sharks, dolphins, and ichthyosaurs also developed a dorsal fin, which further streamlines the body and, in dolphins at least, serves as a display structure.

It is in the forefins that each animal found a different means around the same problem. In sharks, the forefin is made up of straight cartilage spikes encased in a heavy mitten of meat and scale. Sharks do not have wrists or elbows, but only shoulders. The dolphin shortened its arms considerably, retaining an immobile shoulder and wrist, but grew each finger out, like those of a bat, and encased the whole structure in a fleshy mitten. Ichthyosaurs shortened their arms, but increased the number of fingers and individual finger bones. Ichthyosaur hands are made up of a huge mosaic of tiny, rectangular bones that have barely any resemblance to the ancestral tetrapod condition. Look at the picture above! It's hand is basically a solid paddle! But you can see that all three creatures developed certain traits because the environment shapes the animals and plants that live in it.

Humans and the New Environment

Some animals adapt by not adapting their physiology, but only their behavior. "Pest" species are great at this. They take advantage of, namely, humans. Not long ago, pigeons, ravens, and crows all realized that humans leave a lot of waste around, and waste is yummy. New York City has an infamous rat problem, because rats breed quickly and can eat just about anything. In the nutrient-packed human cities, rats and their relatives are becoming the kings. Here in Alaska, bears and moose have quickly adapted to city life, munching on refuse or gardens left behind by people. Sadly, this often results in confrontations between the big mammals and people, and those confrontations usually result in the death of a bear or a moose. Even wolves, those perpetually xenophobic predators of the Alaskan North, have been coming closer and closer toward the city limits in recent years. There have been several sighting by our airport. Wolves are just now learning what bears have known for decades: Trash is free, and people throw out a lot of food! Unfortunately, while some animals are able to generalize their behavior quite well and fit into our modern city life, others are not so lucky. Amphibians and reptiles, especially, are suseptable to pollution and environmental degredation. You can't drive half a mile along a midwestern highway without seeing at least one good-sized mammal or turtle squashed in the road. Sadly, animals that are adapted for a specific environment or behavior are in the most danger from our quickly expanding cityscapes and populations. How does the concept of "change or die" fit into a world that changes quicker than animals can reproduce or survive to find a mate in the first place? Humans have irrevocably changed the face of evolutionary dynamics, and many, many animal and plant species are paying the price.

Above the Natural Law

Tragic though that may be, one of the most interesting aspects of human impact on evolutionary dynamics is that humans now control their own evolution. Whereas mother nature once determined who lived or died, we have gained the incredible ability to shape our own world. Are people being eaten by lions in a village in Africa? Guns, disease, and deforestation should take care of those pesky carnivores. In so many cases, it is the strong that are not surviving, as literacy and education rates have a direct impact on child-rearing. The more educated you are, and the wealthier you are, the less likely you are to have children. But the opposite is also true--the dumbest and poorest among us are the ones passing their genes on. It's actually the complete reverse of natural evolutionary theory--it is the survival of the least fit among humans, and thanks to modern medicine and a host of social and political influences, those children will surely reach sexual maturity and have kids of their own, and the weak shall inheret the Earth.

Humans have forever changed how the game is played, and we must be aware of that. How can we understand how we are changing the world if we do not have the capacity or desire to understand how natural processes work? You can't change what you don't understand, and sadly, that is a prevalent way of thinking in our short-sighted and greedy human society.

Any Questions?

Thus endeth what has become one of the longest posts in When Pigs Fly history. Please, if you have any questions, concerns, or would like to see parts of this lecture fleshed out more, let me know. Also, tell me what you think! I'm considering adding a section on symbiotic relationships, especially between flowers and various animals. And expect another enormous post soon, regarding the History of Feathered Dinosaurs! I may also add to this post in the near future, as I re-read it and find things that need changing or places that need adding-to.