Potentially Inappropriate Posts Part 1: Human Sexuality, Addendum

Tengu commented on my first human sexuality post and pointed me in the direction of very interesting study asking much the same question I did. Why do human females have perpetually large breasts? The study is illuminating, but leaves a few questions unanswered, though I encourage you all to read it. First of all, the authors argue that large breasts got women in hunter/gatherer societies through tough times--they basically acted like camel humps (fat stores). Well, here's my question: why the breasts? They offer tenuous evidence that breast fat somehow converts to milk, but I'd like to see more on that. The human body stores fat in all sorts of places: thights, butt, belly, and breasts. But why would natural selection drive fat stores for women only to the chest?*

Second, it large breasts were so important for early societies, why aren't they strongly written into modern human genomes? The fat-store theory is great, but it implies a pretty strong evolutionary bottleneck--you did not survive the dry season without big breasts. So you get to modern society and women like Amanda Beard** (an olympian swimmer) crop up. Again, I voice a question I asked before: If large breasts confer any kind of advantage, be it for sexual selection or natural selection, why aren't large breasts the standard?

Although, I guess I can't know that for sure. Somebody would have to run one helluva study to figure out the "average" breasts size among various populations of women. Would that average change across traditionally "racial" or culture boundaries? I just got a cool book which features Playboy centerfolds for 54 years, from 1953-2007, and intend to figure out the average myself, leaning on the assumption that Playboy is an accurate barometer of the "American Girl." What I'm finding difficult here is that measurements are not always known and are sometimes simply incorrect, so...yeah***. This is a story for another day, though.****

I don't really see a reason why large breasts can't be the result of both sexual selection and natural selection. It would be advantageous for men to find a naturally selected feature attractive, as it would more quickly disperse that trait among the gene pool. Look at the whole mess of display organs in animals. Dimetrodon has a giant dorsal sail that probably functioned as a thermoregulatory device but could have easily functioned for sexual signaling. Modern giraffes have long necks for both reaching high vegetation (and thus neatly avoiding competition) and battling with rivals. Triceratops had horns and frills that have been shown to have intraspecific display/battle functions, but you can damn well be sure that it's gonna defend itself against a marauding tyrannosaur with that same weaponry. A single structure can have multiple uses.

And another reason why small breasts might successfully "infiltrate" any sort of norm could be just the fact that our genes are spread extremely far, and a whole host of new phenotypes have popped up as a result. And thanks to the same mechanism, no matter what the phenotype, somebody will find it attractive (on a man or a woman), so it successfully remains in that population's gene pool. Anyway, go ahead and read the article, and post your thoughts below!

*And if large breasts are such an advantage during the dry season, why wouldn't other non-human primates develop them?

**Amanda Beard might be a poor choice. Atheletes tend to lose every inch of body fat, especially olympians. Ms. Beard might have had larger breasts before diving into the pool. She's just the only example I could come up with on a whim.

***Playboy likes to pretend the breasts don't get much larger than a DD. There are only four, maybe five examples of playmates with cited busts of DD, and I question whether these measurements are actually too conservative. I could list some names, but this is honestly a topic for an entirely separate post.

****Yes, my wife is aware of the book. She thinks I could publish such a study in a social sciences journal.

Old Castro Got it Wrong...

My ongoing attempts to sculpt a reasonable likeness of Great Lord Cthulhu...um...go on. Here now, I present to you the "final version," which is not, in fact, the final version. This is merely one of two things: 1) The latest version I'm reasonably happy with; or 2) The base by which a true final draft will spring from. After the elephantine horror that came before, I borrowed a few Wayne Douglas Barlowe books from Scott, and became...what's the word? Oh yes, inspired. Barlowe's Expedition may be the best, if not the only illustrative tome to build a convincing alien world up from the ground up. These are not Earthen animals wedged into an awkward alien mold. The critters on Darwin IV would not evolve on Earth, and you have no idea have much I appreciate that. The only other alien monsters I've felt that about are the titular xenomorphs from Aliens, and even they were portrayed by guys in suits (most of the time).

Anyway, I took much from Barlowe's work, but Scott's wager demanded that my starspawn conform to the description put forth by Lovecraft through Old Castro in The Call of Cthulhu. Thus, a vaguely anthropoid outline, a head filled with writhing tentacles, and horrible demon wings were the order of the day. What's an artist to do?

After reading the story a few more times, I realized that Old Castro is, in fact, recalling heresay. He did witness the master of R'lyeh himself, but heard the story from the survivors of that terrible meeting. Additionally, these were terrified men telling the story, their psyches flumoxed by what they were seeing. In my humble opinion, the only concrete physical details of Cthulhu offered by the story are contained in the description of the soapstone relief. Those details are fairly good, but there's another problem to consider: Humanizing our gods. People tend to give their dieties human features, probably so we feel close to them. Geisha, for instance, may have an elephant's head, but it's got a human body...albeit one with too many arms. Finally, Cthulhu's followers were commanded to its will through psychic transmissions given off by the great traveler. Cthulhu may have implanted a false image of itself to calm his chosen. A more humanoid vistage would help to prevent insanity. Or perhaps Cthulhu's followers really did see the beast above but rationalized their god's horrible shape to fit more traditional Earthen imagery.

The underlying reason here is that I'm not doing this shit. Cthulhu is alien, not terran, dammit. I am also operating under the condition that Cthulhu is a real animal, and so must adhere to basic principles of life: it has to eat, sense its surroundings, and generally make a living without relying on magical powers. Cthulhu evolved somewhere.

So here's what Cthulhu is going to have:

1) A large central "trunk" tentacle for manipulating objects;
2) A pair of tentacles with olfactory sensors on their tips (the bulbous ones);
3) A pair of tentacles which are constantly moving, ending in a mass of feathery organs. These feathery organs sense vibration, temperature, and electromagnetic signals. Very handy for a blind creature.
4) A pair of modified feelers just behind the "head" which constantly stretch and retract, moving in all directions at all times, feeling the ground in front of, below, and around Cthulhu;
5) Two large, elephantine legs (the ankle spines will probably go away);
6) A massively fat tail that, from above, looks rather like a devil's tail. The tail is flat (and bright red) across its dorsal surface. Cthulhu stores fat in its tail, which is mobile at its base;
7) Two impressive "wings" which slide open and closed as a Poker player would flare his cards. The wingtips are basically gills, constantly fluttering as oxygen (or whatever Cthulhu breathes) is passed over the fine filaments extending from hundreds of slits on each tip's surface. Cthulhu isn't trying to take flight--he's just breathing;
8) A massive, bulbous "octopus head," which houses a large brain. The large brains size is not exclusively for the production of psychic phenomena testified to by his followers, but rather the mass of sensory information gathered by his armada of feelers and tentacles.

Expect a nicely Photoshopped final version later on, complete with...gasp...a background!

Feathers, Fuzz, and all that Fluff

Feathered non-avian dinosaurs are nothing new. Sinosauropteryx was the first non-avian feathered dinosaur found, in 1996. As a compsognathid, Sinosauropteryx pushes the origin of avian feathers back near the base of the Coelurosauria, a fact which predicts that certain other theropod lineages will also have feathers. And for the most part, these predictions have come true. Dilong is usually thought to be a basal tyrannosauroid*, Beipiaosaurus is a basal therizinosaur, Caudipteryx and Protarchaeopteryx are basal oviraptorosaurs, Jinfengopteryx is a troodontid, and there are a wealth of feathered dromaeosaurs, including Microraptor and Sinornithosaurus. I don’t really know how scansoriopterygians shake out, but they had feathers, too. As more fossils were unearthed, it became clear that feathers come in a wide range of shapes and types. Most non-avian theropods had what I call “baby chicken” feathers—simple shafts which mat together and probably had an insulatory function (as they do in baby chickens). Then, there are “tuft” feathers, in which a multitude of filaments arise from a single point. Think of these as feathers without quills. The next step seems to be quilled feathers lacked individual barbules, so the feathers are frayed and fluffy, like the downy feathers of many waterbirds. Finally, you get a true “modern” feather—one with a quill and branches with barbules that slide together to give rigidity the structure. Only oviraptorosaurs and paravians have true feathers, and only paravians have asymmetrical feathers—those used for flight. So feather evolutions seems to have followed a fairly straight path, from insulating structures (basal coelurosaurs) to display structures (oviraptorosaurs, paravians, scansoriopterygians) to aerodynamic assists (paravians).

Two fairly recent finds have cast doubt on this linear progression of feather evolution. First, a few years ago, a Chinese specimen of Psittacosaurus turned up with absolutely wonderful soft-tissue details preserved, including incredible skin impressions, an “outline” detailing the body’s overall shape, and—most importantly—long, bristly quills erupting from along the dorsal surface of the tail. These quills are circular in cross-section and appear to be hollow. They are not as tightly packed-together as theropod integument, but they are definitely numerous. I was instantly reminded of porcupine quills, although those of the parrot lizard curve gently back. The second find was a new specimen of Beipiaosaurus published earlier this year. It's "feathers" are roughly similar to the parrot lizard in being long, unbranched "quills," although while those of Psittacosaurus are hollow, cyndrical shafts, Beipiaosaurus' quills seem to be flatter. At any rate, Beipiaosaurus' quills look, to me, like very elongate versions of those on Sinosauropteryx.






Just a week ago, we could say with a certain confidence that the quills of Psittacosaurus and those of Beipiaosaurus arose convergently. The great phylogenetic distance between the two taxa, with nary a feathered form in between them argued strongly in favor of an independant acquisition of "quills." In fact, they probably had different functions. In Beipiaosaurus, the feathers thickly cover the entire body and were probably used for thermoregulation. Because Psittacosaurus' quills were only present on the dorsal side of the tail, it's likely they had a defensive or display role (or both). But all it takes is one fossil to throw everything paleontologists think they know into question, and one of those fossils was published in this week's issue of the journal Nature.




Behold! Tianyulong confuciusi, a feathered heterodontosaur from China. Now, just to remind you all where heterodontosaurs sit on the dinosaur family tree, a recent reappraisal of basal ornithischians by Butler et al. (2007) suggested that heterodontosaurs represent the basalmost formal group of ornithischians (no more "fabrosaurs" here!). So we've got a ridiculously basal ornithischian with feathers, an incredibly derived ornithischian with "quills," and a whole bunch of coelurosaurs with feathers. But then you've got a whole mess of dinosaurs in between with preserved skin impressions showing scaley, reptilian skin. Does this mean the integument of ornithischians is non-homologous to the integument of saurischians? Well, not necessarily. There may be several factors at play here. "Feathery" integument could be basal to all of the Dinosauria, but may be a juvenile character. The peach fuzz is present on hatchlings but lost upon reaching adulthood. In some dinosaur groups, coelurosaurs and heterodontosaurs, for example, that peach fuzz is retained into adulthood (ontogeny). Or perhaps only small dinosaurs had feathers, or at least those below a certain maximum mass. Large-bodied mammals often have extreme short, fine hair or have gone "bald" entirely. Elephants, hippos and rhinos have all convergently developed hairless bodies, probably in response to the hot temperatures they operate at. Even naked, these animals need to cool off in mud or waterholes. Many dinosaurs became rhino or elephant-sized (or much, much larger), so you wouldn't expect to see feathers on an animal the size of Triceratops or Sauroposeidon. Maybe decorative patches here and there, but certainly not the extent of Sinornithosaurus. Ornithischians could've just used feathers in a different way--Psittacosaurus only retained them on the dorsal surface of the tail, after all, and probably used them for defensive display. The parrot lizard certainly isn't at the theoretical maximum size to still have a full coat of feathers. It's hardly bigger than Beipiaosaurus, which itself is fully fluffed up.


On the other hand, there's a strong preservation bias against feathers. You only get good evidence of feathers on a slab fossil like Archaeopteryx or Tianyulong. You won't find fuzz on a 3D fossil, and that's how larger dinosaurs come out of the ground. Even so, the size assumption does seem to pan out. Skin impressions from a wealth of giant dinosaurs have shown that their skin is pebbled, not feathered. So maybe feathers are basal to all of the Dinosauria, but many groups, including thyreophorans, hadrosaurs, and sauropods secondarily lost their plumage entirely. One thing does seem clear--of all the dinosaur groups where integument of any kind is known, only one small branch of the Theropoda developed true feathers--the kind that gets you up in the air. If the feathers on Psittacosaurus, Tianyulong, and Baipiaosaurus really are homologous, then feather structure remained relatively conservative across the spectrum, and only got the "next stage" in the theropods. Tianyulong's authors note the differences (mostly in cross-sectional shape) between the feathers of the heterodontosaur and the therizinosaur, but these are fairly minor quips. Aside from one being circular and the other being flatter, they look startlingly similar. I would be genuinely surprised if "feathery" integument was not basal to the Dinosauria at this point.


But wait--there's more! Check out those pterosaurs. They all had some kind of fuzz, too. It's usually thought to have arose separately, but what if, just what if, the integument of Sordes 'n' Pals is homologous to the integument of Tianyulong and Baipiaosaurus? That would mean that all ornithodirans, basically everyone from pterosaurs to dinosaurs, was fluffy to some degree. Marasuchus, Silesaurus, nobody's safe. They might've all had feathers.






The fact that all of the Ornithodira could be fluffy has enormous consequences for paleontology. First of all, it probably means that ornithodirans were endothermic. Ectothermic animals, today anyway, don't have hairy or feathery integument. No hairy lizards or feathery turtles, I'm afraid. Interestingly, the one mammal that has reverted to ectothermy, the naked mole-rat, has lost its furry coats--without the ability to generate heat internally, it has no need to try and retain that heat, so the hair disappeared. Naked skin seems to equal ectothermy, and fuzzy skin seems to equal endothermy. That doesn't mean dinosaurs that secondarily lose their feathers reverted to ectothermy. Far from it! The larger an animal gets, the more dangerous a coat of hair or feathers becomes. African elephants don't have mammoth coats of hair because if they did, they'd overheat. They have enough problems maintaining their body temperature at a reasonable constant with all that surface area, thank you very much. I imagine the same problem plagued sauropods, hadrosaurs, and ceratopsians. For those guys, a coat of feathers would've been suicide.


But wait--there's more! Suddenly, dinosaurs who live in Alaska, Russia, and Australia have a way to beat the cold! Now granted, temperatures in Cretaceous Alaska never reached the horrible lows we see today, but ice would've formed in the winters, and snow may have fallen. Australia faced much the same situation, and Siberia probably did, too. Alaska and Siberia were farther north, and Australia was farther south. All this time, paleontologists have been suggesting migration or hibernation for high-latitude dinosaurs, but now that fuzz has come along on ornithischians, little Leaellynasaura suddenly has a way to insulate against those chilly twilight nights. Now, up in Alaska, I'm not saying that larger dinosaurs (like Edmontosaurus and Pachyrhinosaurus) did NOT migrate south, but maybe they adapted to the cold in the same way that Pleistocene megafauna did: grow a thick, lusterus coat of fluff in the winter, and shed most of it in the summer. Of course, skin impressions from Alaskan specimens would help, as would publication of the material coming out of the Colville. Our Pachyrhinosaurus might be a distinct species, but nothing substantial has been published on it.

So there you have it, folks. Feathered heterodontosaurs are ridiculously exciting for a number of reasons. Now, this initial find should be treated with some caution. It's not uncommon for Chinese fossils to be faked somehow, and I'd like to see more ornithischian families discovered with evidence of feathers before the idea of feathers being plesiomorphic for Dinosauria is really cemented. Still, it's one helluva step forward.

*There is increasing doubt, however, that Dilong and Guanlong are ancestral tyrannosaurs. Instead, they may simply represent forms which fall between Ornitholestes and compsognathids. This would actually be helpful, as it would mean the origins of feathers are pushed to the very base of the Coelurosauria.

Proactive dicynodonts

Remember this guy? It's Odobenodon bairdi, a thought experiment designed to deduce what some Permian critters would have evolved into had the Permio-Triassic extinction not occurred. It's a project I'm working on with Will Baid of The Dragon's Tales. Anyway, this was my first pass at the "walrodont," as we're calling it, and it looks bad now. I'm continually reworking the animal's gross morphology. Skull doesn't make sense, limbs are too long, etc. But I do like the idea of a walrodont, though the more I think about it the less it makes sense.

Anyway, two new critters have popped up. Transitional forms between a walrodont and your average dog-sized dicynodont. First is the "hippodont," an animal not that different from your garden-variety Placerias, but bulkier. We haven't decided on a formal name yet, but I like him!

Forelimbs sprawl, hindlimbs are held erect. All I know about dicynodonts, I learned from Will Baird. They're very strange critters, totally unlike anything that's come before or since. The next up is the "desmodont," sort of a cross between a dicynodont and a desmostylan. I figured that the first tentative steps into a marine environment would be more like paddles, and desmostylans have been compared to paddling bears before (I don't have the citation right in front of me), so they seemed like a good model.

No formal name here, either. I can definately see this creature evolving into the walrodont at the top of the post, although the walrodont needs some major changes. In fact, I've since come up with a new walrodont, but I had it almost as much. Here it is for comparison's sake:

Oh, geezus, look away! The hindlimbs are all wrong, and the forelimbs are too...bulky! I'm starting to think that dicynodonts would go the way of sirenians--eliminate the hindlimbs entirely, but that makes landlubbing something of a problem. So the walrodont is tough for me. But like I said, dicynodonts are new to me. If anyone has helpful PDF's, especially any detailing their cranial anatomy or general skeletal build, that would be enormously helpful. Anyway, these are the "new" dicynodonts. What'cha'll think?

Allah Forgive Me...

I've crumbled to peer pressure and have joined the online community that is Facebook. Just search for Zachary Miller and add me as your friend. Seems harmless enough, and you'll probably see pictures that aren't here on the blog for whatever reason.

I'm also on Myspace, but I barely ever check it anymore. Thought you all should know.

Club Mixes

What's the goddamn point?

Is the original song not tech-no-ee enough for you?

The Einiosaurus Sequence

For all of you who've been to the new Art Evolved art show, my Einiosaurus growth sequence may already be familiar. Well in this humble post, I will delve into how such a drawing came to be. For the uninformed, here is the final product (it's actually not the final product, as I intend to significantly rework it):

Anyway, check that out. Things I want to do to it in the future: Put quotation marks around Brachyceratops and Monoclonius (don't know why I forgot that one!), give all the heads scales, eliminate the "grown-together" look of the epocciptals, and add rows of scutes going down the center of the parietal and the squamosal-parietal contact. Andrew Farke also suggested toning down the coalescence of the keratin on the face. He says the postorbital and nasal horns would have very separate origins, more like you see in traditional restorations. So that's a future project.

Anyway, the picture was always going to be a growth series, as I'd been reading a lot about centrosaurine ontogeny lately. The original plan was to have a big adult Einiosaurus defending a younger female and a baby animal against a marauding Daspletosaurus. But because I am who I am, I quickly found myself panicking against a looming March 1st deadline, so I scrapped the "scenic" approach and focused exclusively on the animal's noggins, which is where the biggest changes occurred anyway. I initially did inked sketches of all three animals...

Hideous little Brachyceratops there. I was initially forcing myself to get out of my habit of drawing animals in profile only. I could've reworked this little guy and keep the 3/4ths view, but I think the transition is more obvious in profile view. However, for my upcoming Ceratopsia project, I'm gonna have to get used to the 3/4ths view.

The Monoclonius was reworked from M. lowei to reflect differences in the nasal horn. In M. lowei, the horn is much smaller and recurved. It is, however, clearly a different animal than Centrosaurus apertus, which every other "Monoclonius" was reassigned to. Whatever M. lowei is, it must be a subadult of a "straight-back" frilled centrosaurine. Einiosaurus isn't a bad match, all things considered. I'm bothered by the recurved nasal horn, but, of course, centrosaurines go through more severe changes than that, and the postorbital horns of Triceratops went from stubs to recurved to straight to procurved duriung growth, to I guess anything's possible.

Aaaand here's the big bull's skull. This was the first piece of the puzzle, actually. Andrew Farke okayed it, suggesting only that I modify the shape of the pariatal-squamosal suture. He was also kind enough to send me a photo of an Einiosaurus squamosal so I could get a better idea of its shape.

And here is the first draft of the bull with skin on its face. It's much sketchier than the final draft, and the fleshy nostril is too far away from the nose. Andrew suggested I move it down and closer to the rostral bone to make it "more Wittmorian." Since this sketch was done more or less by tracing the skull (above), the parietal-squamosal contact is still incorrect.

And then you have the finished version (at the top), which was done by scanning all these pictures into Photoshop Elements and coloring them separately (copy base layer + multiply!) and then stitching them together in sequence. You'll notice I changed the Brachyceratops. I did that to make the sequence look smoother, so that all parts of the skull could be compared. I'm not actually done with the piece, either. Scott did a cool "scale" effect on his Pachyrhinosaurus that I'd like to implement here, and I'd like to put little scutes going down the center of the parietal and the parietal/squamosal contact. Finally, I need to tone down the intergration between the epoccipitals and between the nasal and postorbital horns. Aaaand maybe add some background color. And some explanatory text, including throwing some quotation marks around "Brachyceratops" and "Monoclonius."

Potentially Inappropriate Posts Part 1: Human Sexuality, Part 2

Yesterday we discussed how women are the peacocks and men are the peahens in terms of who is wooing who in the species Homo sapiens sapiens. I attempted to demonstrate that one of the "big guys" that women have for attracting the opposite sex are her mammary glands (exemplified by Salma Hayek, to the left). Well, let's talk about that...er, those.

Most mammals have more than two "breasts." In fact, it's difficult to call what most mammals have "breasts." Most mammalian females have multiple nipples connected to mammary glands that swell with milk when babies are around. Mammary glands are a defining character of mammals, of course. They began their evolutionary history as modified sweat glands--a form retained in monotremes. In other mammals, mammary glands expanded to include several distinct nipples. Have you ever seen a big momma pig on her side with a dozen piglets suckling happily? In every non-human primate, mammary glands are specifically for feeding the young. Male pigs don't get all excited when they see a big mammary gland hanging from the belly of a sow. And male non-human primates could care less about female breasts, even when those glands are swollen. Monkeys and apes are more...well, ass-men. The female posterior swells during estrus and the males start hootin' and hollerin'.

But human females are the only mammals with perpetually swollen breasts, leading most to conclude--quite rightly--that breasts serve an important secondary function. As I said before, they're the equivalent of ceratopsian neck frills. It's hard not to swivel your head when a girl like Salma walks by. But here's a question for you. Has the advertising power of breasts overpowered the baby-feeding role? That is, among human females, is nursing now the secondary purpose of breasts? Is showin' them off the primary purpose?

Breast implants show up pretty early in American girls. Sue Williams was the first Playmate to have implants--in 1965. However, breast enhancement wasn't the safe science it is today. Silicone was injected directly into the breast tissue, often multiple times. This led, invariably, to cancer in many women. Later implants were considerably safer: saline implants preceded silicone gel implants. Both have their own set of problems, including the risk of rupture and the sometimes-hideous visual results. Breast implants are invariably tougher and thicker than breast tissue itself, and although they may be visually attractive, people tell me they're not all that fun in...the...sack. And there's another gigantic downside to breast implants:

In some cases (this depends primarily on the implant's size), breast implants impede the ability to nurse. Did you hear that? In addition to the health risks caused by the surgery, the foreign material in the body, and the recovery afterward, you might not be able to nurse your babies!

But why do women get breast implants in the first place? Two primary reasons, I think:

1) Attract the opposite sex, and;

2) Reconstructive surgery after damage to the breast because of cancer or injury (or masectomy).

The first reason is undoubtably the most common. And think about it--that's a helluva gamble. Your risk your own life on the surgery table in hopes of attracting the opposite sex, which reproductive drive tells you to mate with and procreate, but then, hold on--you might not be able to feed the baby! That's...incredible! Breasts have switched from being primarily for feeding babies to attracting mates. No other animal does this! But again, I ask about technology and medicine. Certainly breast implants would not be as popular were it not for advances in medicine that make them safer. What's more, women don't always feed their babies with their own breastmilk. There are wet nurses and bottles for that. Of course, both are potentially inferior, as the mother's milk passes on important immune agents to the baby. It's that crazy? It boggles my mind, honestly. We're so happy with our technology and medicine that the very organ that makes us mammals is losing its defining purpose. That's epic stuff.

Potentially Inappropriate Posts Part 1: Human Sexuality, Part 1

I like dinosaurs, gaming, paleontology in general, movies, very few comics (mostly webcomics at this point), H. P. Lovecraft, and...wait for it...women. I know, I'm a bad person. But don't worry too much, it's not a "ooh, boobies!" kind of thing (although there's some of that, too). Modern man has some backwards sexual tendancies compared to most of the rest of the vertebrate community, especially other mammals or, heck, non-human primates.

And it's something that interests me. Time to be totally up-front here: I'm a breast man. Thus, the picture at left (Denise Milani). I also prefer an hourglass figure. I don't think these are bizarre human male tendances. They must mean something, right?

But why do I like breasts and an hourglass figure while my friend Luke likes legs and a tone midriff? Why does my friend Erik like butts and...a tone midriff? Why do both of them (and some of my other friends) prefer smaller breasts?

In a total reversal from most other vertebrate animals, it is the females of Homo sapiens sapiens that are the sexual "billboards" (in general). Big breasts, long legs, tone midriff (don't understand that one), bubble butt, these are all desirable traits. But in most non-human vertebrates, males compete for females by being billboards. Ceratopsians had giant frills and big horns. Male elephant seals are enormous, blubbery, and have trunks. Male baboons have bright faces and giant canines. Male birds of paradise are ridiculously colorful and have bizarre plumage that's useful only for attracting the opposite sex. But women have breasts, butts, and legs, which they show off with swimsuits, low-cut tops, and short skirts. Men can do the same thing, but the opposite effect is usually achieved: no woman I've ever met likes a guy with super-huge muscles, for example.

Another interesting reversal is the breasts themselves. In non-human primates, breasts are used primarily to nurse the young. Males are attracted to the females posterior when it becomes swollen during breeding season (that's estrus). Humans don't really go through a visible estrus cycle (although that's debatable), so the butt was replaced by larger breasts. But there's a tradeoff here--breasts don't just swell and shrink depending on the season. They stay large! So human females are essentially advertising their sexuality all the time, and clothing is used to openly advertise it or not. Men, however, do not have such obvious sexual organs. Facial hair may be the male "billboard," but it doesn't have the same draw as...well, Denise up there. In Homo sapiens sapiens, the females are primarily competing for male attention instead of the other way around.

You can see this yourself by going to a bar or pool hall on the weekend. Men dress casual, in T-shirts and jeans, but women use perfume and revealing clothing to attract attention to themselves. If men and women were peacocks, the sexes would be reversed! The females would have big showy feathers, and males would be duller-colored.

But here's where another question comes to mind: Are there universally attractive female features? Clearly not, as a quick survey by my friends reveals. But why is that? You don't see that kind of selectiveness in non-human animals. Female moose are going to mate with the toughest male with the largest antlers. Although my field experience in close to nill, I would think that females aren't saying to each other, "You know, I really like a male with big kneecaps." Females like antlers. Protoceratops females liked vaulted nasals on their males and big frills. Yowza! So what about humans? Why don't males across the species harbor similar desires for certain female features? Let's say that hourglass figures are an indication of fertility (which has been theorized!). Why would any man prefer a woman with anything but an hourglass figure? We could say the same thing about breasts: let's assume that large breasts are an indication of increased milk production (as has although been theorized). Why would natural selection favor anything below a C-cup?

Could this be an indication that natural selection isn't working in humans like it used to? Because medicine and technology keeps us all alive and breeding, those phenotypes which would otherwise be "bred out" of the gene pool stick around, and when you get to 6 billion+ people, sexual preference among males is also going to expand, too. Maybe when humans were hunting bison with spears and living in caves, sexual selection was more strongly universal, but as populations increased and lifespans lengthened, those factors were toned down. And today, you have every body type imaginable wandering the planet, and everybody will find somebody thanks to the miracle of overpopulation.

But there is still a very strong tendancy for women to be the "advertisers," which is interesting. I also wonder if, besides having a biological component, cultural factors differ between distinct human populations (more on that in future posts) in terms of who is competing for who?

More on this point in a future post. Feel free to call me a jackass in the comments, but this is interesting stuff. I like placing humans in the same scientific context that we would any other animal!

Important warning: If you're a woman, and you're wearing a low-cut top or a bra that emphasizes your cleavage, and you meet me, you'll have to excuse my descending gaze. I know your eyes up "up here," but goddamnit, it's not personal! Also: Don't avoid said types of clothing on behalf. :-D

Theropod Handprints & Their Implications

Put your hands out in front of you, palms facing together. That's how theropod dinosaurs held their hands. Now lower your hands so that they're resting on your desk, and let your fingers assume their natural curl. That's how theropod dinosaurs rested their hands on substrates! Usually, you see restorations of theropods with their hands held palm-down, like Mr. Burns on the Simpsons holds them, or the "Velociraptors" in Jurassic Park. Well, paleontologists have known for years that most theropods--at least, all the ones with preserved wrists--were simply unable to assume such a posture.

Humans (and non-human primates) are able to "twist" our wrists because our radius basically moves over the ulna. Let's do an experiment.

Put your arms straight out at your sides, palms facing forwards. Now, move your palms so that they face down. That's called pronation. Now, move your palms back to face fowards. That's supination. Put your arms back down to your side--that's adduction. Move them back out, and that is abduction. Now, raise your arms over your head. The movement at your shoulders is called protraction. Move them back down, and it's retraction.
Okay, relax. Put your arms down to your sides. We'll do wrist exercises. Move your wrist so that the back of your hand forms a right angle to the back (hairy side) of your arm. That is hyperextension. Move it the opposite way, and it's flexion. Go back to neutral and that movement is called extension. Let's do two more: bend the wrist down so that you try to form an angle between the pinky side of your hand and your ulna. That's a tough one, right? It's called, predictably, ulnar adduction. Try bending your wrist the opposite way--that's almost impossible for humans, and it's called radial abduction.

So it turns out that theropod dinosaurs couled not pronate or supinate their arms, so "twisting" the wrist was impossible. However, they were very good at flexion and hyperextension. As theropods evolved, they became better and better at ulnar adduction. Furthermore, theropods were able to hyperextend their fingers--even early theropods like Coelophysis. The osteology of theropod hands is quite well known thanks to Carpenter's excellent work in 2002. In all, theropods in general were good at clutching things close to the chest. Let's do one more pantomime experiment to illustrate theropod arm movement.

Stand up and bend over slightly, drop your arms towards the ground, and rotate your wrists so that they're facing each other. Bend at the elbow slightly, but keep your wrists straight--in line with your lower arm. Curl your fingers and hands toward your chest as if you're trying to hold something. Now, relax your fingers while moving your arms up toward your sides (movement should be restricted to your shoulders). Stop when your arms naturally assume horizontal position. That's about how a theropod moved its arms up and down. If you want, you can protract your shoulders, but only to the point where a right angle forms between your upper arm and your side--most theropods were unable to protract beyond that point.

So the osteology is well-known. Theropods developed fairly avian arm joints early in their evolution. But wouldn't it be nice to see evidence of that in some other way than playing around with arm bones? Well guess what, kiddies--it's here!

If theropods were able to somehow able to hold their hands palm-down, you'd think that, eventually somebody would find an ichnofossil of a theropod hand, palm-down, in line with the feet. Milner, et al. reported yesterday on a resting trace of a probable coelophysoid dinosaur with manual handprints, and they show conclusively that theropods rested their hands pinky-side down, as I described in the first paragraph! The animal is sitting on the beach of an ancient lake. It is resting on its ischial collosity, with the whole foot on the ground. There are even some tail drag marks. But most importantly, there are well-defined manual impressions, and they show claws marks pointing inward and the pinky edge of the hand against the ground. So it would seem that, even among primitive theropods, the hand was habitually carried this way. The excellent picture at the top of the post is by Heather Luterman, and I recommend checking out her site! I especially like her Ambulocetus!

Milner, A. R. C., Harris, J. D., Lockley, M. G., Kirkland, J. I. & Matthews, N. A. (2009). Bird-like anatomy, posture, and behavior revealed by an Early Jurassic theropod dinosaur resting trace. PLoS ONE 4(3): published online.

Carpenter, K. (2002). Forelimb biomechanics of nonavian theropod dinosaurs in predation. Senckenbergiana lethaea 82(1): 59-76.

Art Evolved!

The wait is over. A few months ago, Traumador emailed me and offered a spot on the staff of a new paleo-blog called Art Evolved. His goal (I think) was to build a site where paleoartists from around the web could gather and show off their art and enthusiasm for their subject matter. I leapt at the opportunity. Well, after about four months, the site is now LIVE, and the first art show has been posted! More entries may leak in during the coming days, so check back now and again. I'm very excited about this project--the first show concerns ceratopsians (thus, my recent obsession with them), and it's really fantastic, spared no expense.

So head on over to Art Evolved: Life's Time Capsule and take in the horned dinosaurs!