Courtesy M. R. Smith / Smithsonian InstituteOne of the strangest and more mysterious critters that scurried across the Middle Cambrian seafloor has baffled paleontologist since it was first identified in the 1970s. Was it a worm? Which side was up? Did it have legs or spikes or both? Was its head actually its tail? Did it have any extant descendents or was it an evolutionary dead-end? The worm-like creature was so baffling and so bizarre, it was given the very apropos name of Hallucigenia.
The tubular, spiked-worm possessed seven or eight pairs of legs and ranged in length from 2/5th of an inch to one and 1/4 inches and looks like something out of a bad dream. Early interpretations of their fossils were all over the map. The stiff spikes on it back were first thought to be its legs, and its legs misidentified as tentacles. What was thought to be its tail ended up being its head.
Using modern imaging technology, researchers from the University of Cambridge have been closely studying fossils from the famous Burgess Shale quarry located high in the Canadian Rockies, and are uncovering Hallucigenia's secrets. By studying the claws at the end of its legs they have been able to link it to modern velvet worms (onychophorans). Scientists have long suspected the two were somehow related but until now have failed to find anything significant to prove it. By studying Hallucigenia's claws they've determined that they're constructed of nested cuticle layers, very similar to how the jaws of velvet worms are organized. The similarity is no surprise since jaws are known to have evolved from a modified set of front legs.
But besides giving Hallucigenia a place in the lineage of life on Earth, the Cambridge team during the course of their study also discovered something else: that arthropods - which include crustaceans, spiders, insects and trilobites - aren't in fact as closely related to velvet worms as previously thought.
“Most gene-based studies suggest that arthropods and velvet worms are closely related to each other," said co-author Dr Javier Ortega-Hernandez. "However, our results indicate that arthropods are actually closer to water bears, or tardigrades, a group of hardy microscopic animals best known for being able to survive the vacuum of space and sub-zero temperatures – leaving velvet worms as distant cousins.”
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Courtesy Fancy Horse (underwater background)The genome of the coelacanth, the world's best known living fossil, has been sequenced by an international team of researchers and is revealing something scientists already suspected: that the primitive-looking fish has evolved more slowly than most other organisms. The coelacanth is related to the lungfish and several extinct Devonian fish species that are considered precursors to land dwelling tetrapods. Kerstin Lindblad-Toh is senior author of the study which appeared recently in the science journal Nature.
"We often talk about how species have changed over time, but there are still a few places on Earth where organisms don't have to change, and this is one of them," Lindblad-Toh said. "Coelacanths are likely very specialized to such a specific, non-changing, extreme environment -- it is ideally suited to the deep sea just the way it is."
Lindblad-Toh is scientific director of the Broad Institute's vertebrate genome biology group in Cambridge, Massachusetts, which did the genome research. The institute is linked to both MIT and Harvard.
The genetic map, which involved sequencing some 3 billion letters of DNA, also showed (via RNA content) that tetrapods - four-legged land dwelling animals - though related to both coelacanths and lungfish, are more closely related to lungfish and followed that line rather than that of the coelacanth. We humans also branched off that same line. The genome of a lungfish is composed of over 100 billion DNA letters, making it a much more difficult task to sequence, so for the time being, the coelacanth's DNA makes for a reasonable alternative for study.
"This is just the beginning of many analyses on what the coelacanth can teach us about the emergence of land vertebrates, including humans, and, combined with modern empirical approaches, can lend insights into the mechanisms that have contributed to major evolutionary innovations," said professor Chris Amemiya at the University of Washington, and the paper's co-author.
Courtesy photo by Haplochromis via Wikipedia Creative CommonsWhen Louis Agassiz named the first fossil coelacanth back in 1836, the Swiss paleontologist probably never imagined that a nearly identical descendent of the primitively constructed Devonian-aged fish would one day be found still inhabiting the world's oceans. The coelacanth was thought to have gone extinct along with the non-avian dinosaurs at the end of the Cretaceous period. None have been found in the fossil record after that time, but two extant species are known today. The first specimen Latimeria chalumnae was netted off the coast of South Africa in 1938, near the Chalumnae river and retrieved by East London Museum curator Marjorie Courtenay-Latimer who discovered what she called "the most beautiful fish I'd ever seen" in the catch of local fisherman, Henrik Goosen. Since then several more coelacanths have been caught, including the Indonesian species, Latimeria menadoensis, from the Indian Ocean.
The remarkable prehistoric throw-back, sometimes referred to as "old four legs" because of its leg-like fins, hasn't changed much in its 350 million year history. A member of the clade of lobe-finned fishes called Sarcopterygii, coelacanths retain primitive characteristics such a notochord, a hollow fluid-filled tube made of cartilage that underlies the spine over the length of its body. In all other vertebrates, the notochord is an anatomical structure that appears briefly only during the embryonic stage but not in adults. Not so with the coelacanth. It also possesses, primitive shark-like intestines, a linear heart, and tightly-woven armor-like scales (known as cosmoid) that are only found on extinct species of fish. The coelacanth's brain case contains only 1.5 percent gray matter - the other 98.5 percent of space is filled with fat. The other end of the coelacanth body begins to taper before expanding into a strange, three-lobed tail. Its most notable features are its lobed pectoral and pelvic fins that are structured with bones that look like toes, and move in an alternating tetrapod manner. An electroreceptive rostal organ located in its snout is used to detect prey, and the coelacanth is the only living animal that can unhinge a section of the its cranium to increase the gape of its mouth, enabling it to consume larger prey.
The blue or brown, white-speckled coelacanths prefer deep-water environments, and can reach six and a half feet in length and weigh upwards to 175 pounds. For some reason no living coelacanth has managed to survive more than a single day in captivity. With a dwindling population estimated at only 500-1000 individuals, the coelacanth was declared an endangered species in 1989.
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Courtesy C-MOREHow would you like to be aboard a ship, circumnavigating the globe, collecting samples from the world’s ocean?
That’s exactly what Spanish oceanographers are doing on their Malaspina Expedition aboard the Research Vessel, R/V Hespérides. Scientists and crew left southern Spain in December, reached New Zealand in mid-April, and recently arrived in Hawai`i. The expedition's primary goals are to:
Courtesy C-MOREIn connection with the latter two goals, the Malaspina scientists met with their colleagues at the Center for Microbial Oceanography: Research and Education (C-MORE). The two groups of scientists are working together. "We can exchange data on the local effects, what's happening around the Hawaiian Islands, and they can tell us what's happening in the middle of the Pacific," said Dr. Dave Karl, University of Hawai`i oceanography professor and Director of C-MORE.
The Malaspina-C-MORE partnership is the kind of cooperation that can help solve environmental problems which stretch beyond an individual nation’s borders. The R/V Hespérides has now left Honolulu on its way to Panama and Colombia. From there, the scientists expect to complete their ocean sampling through the Atlantic Ocean and return to Spain by July. Buen viaje!
Courtesy Hans-Petter FjeldBuckle up, Buzzketeers, because school is in session.
Did I just mix metaphors? No! You wear seatbelts in my school, because they help prevent you from exploding.
But you will probably explode anyway, because you are going to get taught. By JGordon. About the future.
Here’s your background reading: a GMO is a genetically modified organism—a living thing whose genetic material has been altered through genetic engineering. Humans have been genetically modifying plants and animals for thousands of years (by selectively breeding them for desired characteristics), but it’s only been in the last few decades that we’ve gotten really fancy and fast about it.
While in the past, or what I like to call “the boring old days,” it took generations to breed crops that produced high yields, grew faster, or needed less water, we can now do that sort of thing in an afternoon. (Well, not really an afternoon, but these aren’t the boring old days, so we should feel free to use hyperbolic language.) We can insert genes from one plant into another, bestowing resistance to pests or poisons, or increasing the nutrition of a food crop.
Pretty cool, right? Maybe. GMOs tend to make people uncomfortable. Emotionally. They get freaked out at the thought of eating something that they imagine was created like the Teenage Mutant Ninja Turtles. Most people prefer to eat stuff that was created the old fashion way: through SEX.
Once they’re in your tummy, GMOs are probably pretty much the same as any other food, really. However, there may be other reasons to approach them cautiously. Most organisms make a place for themselves in their environment, and their environment makes a place around them, and things tend to work pretty well together. But GMOs are brand new organisms, and it can be very difficult to tell how they’ll fit into the rest of the natural world. Will they out-compete “natural” organisms, and cause them to go extinct? Will they interbreed with them, and introduce new weaknesses to previously strong species? The repercussions of such events could be… well, very bad.
On the other hand, GMOs could provide food—better, more nutritious, easier to grow food—for people and places that really need it. And with global population expected to increase by a few billion people before it stabilizes, we’re going to need a lot of food.
Just like everything else, this stuff is complicated. Really complicated. But the issue isn’t waiting for us to get comfortable with it before it pushes ahead. Hence, our main event: GMO salmon.
You might not have devoted much mental space as of yet to mutant ninja salmon, but you will. See, transgenic salmon (i.e., salmon with genes from other animals) may be the first GMO animal on your dinner plate. Or whatever plate you use for whenever you eat salmon. If you even use a plate, you animal.
What’s the point of the GMO salmon? In the right conditions, they grow much faster than their normal counterparts, and they require about 10% less food to reach the same weight as normal salmon. The company responsible for them, AquaBounty, has been working on the project for more than 20 years. Inserted into a commonly farmed species, the Atlantic salmon, the final, successful combination of genes comes from Chinook salmon (a closely related, but much larger species) and the ocean pout (a slightly eel-like fish that can tolerate very cold water). While Atlantic salmon typically only grow during the summer, the new variation produces growth hormones year round, so they can grow to marketable size in about 60% of the time it would normally take, assuming they’re kept in water that’s at the right temperature, and given plenty of food year round.
While some people object to GMO foods on the grounds that the long-term effects from eating them are unknown, probably the more salient argument is the effect they might have on the natural world. A larger, faster growing species could put tremendous pressure on already stressed, wild Atlantic salmon. AquaBounty counters that in normal ocean temperatures, the GMO salmon would grow no faster than wild salmon. Also, all of the GMO salmon are female, and 95 to 99% of them are sterile (they can’t reproduce). And none of that should matter, because the salmon will be raised in tanks, away from the ocean.
Even if they are successfully isolated from wild salmon, opponents point out, that doesn’t mean they are isolated from the environment. See, salmon eat other fish, and it takes about 2 pounds of other fish to make one pound of salmon (according to this article on the GMO salmon). Large amounts of the kinds of fish people don’t eat are caught and processed to feed farm-raised salmon. If cheaper, fast-growing salmon cause the demand for salmon to rise, more food stock fish will have to be caught to supply the farms, putting pressure on these other species.
Courtesy Dark jedi requiemThen again, if the GMO salmon can be raised successfully and profitably in inland tanks, it could remove other negative environmental impacts. Aquaculture fish farms are typically in larger bodies of water, with the fish contained inside a ring of nets. The high concentration of fish in one area leads to more diseases and parasites, which can spread to nearby wild fish. Salmon farms also produce lots of waste, and it’s all concentrated in one spot. Supposedly, a farm of 200,000 salmon produces more fecal waste than a city of 60,000 people. (That’s what they say—it sounds like a load of crap to me, though.)
It’s a tricky subject, and anyone who says otherwise is being tricky (ironically). Nonetheless, it seems likely that the Food and Drug Administration will soon declare this particular GMO as officially safe to eat, and GMO salmon fillets could make their way to the supermarket in the next couple years. Even if the FDA didn’t approve the fish, however, that would only mean that it couldn’t be sold in the US—the operation could continue to produce fish for international markets.
GMO salmon are just the tip of the GMO animal iceberg (if you’ll forgive the iceberg analogy—I don’t mean to imply that they are going to sink us.) The next GMO in line for FDA approval, probably, is the so-called “enviropig,” a GMO pig with a greater capability to digest phosphorus. This should reduce feed costs, and significantly lower the phosphorus content of the manure produced by the pigs. That’s important because phosphorus from manure often leaches into bodies of water, fertilizing microorganisms, which, in turn, reproduce in massive numbers and suffocate other aquatic life.
As the human population grows and needs more food, genetically engineered plants and animals are going to become increasingly common. They might make the process of feeding and clothing ourselves easier and more sustainable. Or they might royally screw things up. Or both. So start thinking about these things, and start thinking about them carefully.
Er… so what do you think about GMOs? Are they a good idea? Are they a good idea for certain applications? Are they a bad idea? Why? Scroll down to the comments section, and let’s have it!
Courtesy Mark RyanThe bone of a single pinky finger found in a cave in southern Siberia may indicate a new branch in the human family tree. The find could show that besides Neanderthals and Homo sapiens, a third lineage of humans may have shared the ancient landscape of prehistoric Russia.
The piece of finger was found in Denisova cave located in Russia’s Altai mountains by scientists from the Russian Academy of Science. The bone was recovered from sediment layers that have also yielded signs of Neanderthals (Homo neanderthalensis) and modern humans (Homo sapiens). Radiocarbon dating set the age of the layers between 48,000 and 30,000 years old.
Scientists from Germany’s Max Planck Institute and others sequenced 16,569 base pairs of the finger bone’s mitochondrial DNA genome, and the results indicate the new hominen shared a common ancestor with both neanderthals and ancient modern humans sometime around a million years ago. The research team included Michael Shunkov and Anatoli Derevianko, the two Russian archaeologists who discovered the bone in 2008. The study appears in the journal Nature.
Further sequencing of DNA from cell nucleuses will be done next, and could help pinpoint the hominen’s exact origins. If confirmed, the discovery would mean four different species of humans (the 4th would be the Indonesian Hobbit Homo floresiensis) co-existed on Earth some 40,000 years ago.
Courtesy Nino BarbieriA recent article in the Journal of Archaeological Science reminded me of the importance of the Scientific Method Often we hear new and exciting scientific theories that seem plausible, especially if these ideas are presented in prestigious journals. However, the beauty of the Scientific Method is its verifiability, whether or not the data can be recreated through repetitive testing (If we truly believed everything the first time, our budding young scientists would have nothing to do!)
Michael Campana from the University of Cambridge and colleagues from across the UK and Ireland recently ran a sequence of DNA tests on 18th and 19th century parchments made from animal skins in order to reveal the complexities of ancient parchment analysis. Parchment is one of the most valuable archaeological and historical artifacts that can be used to understand not only language and history, but DNA testing on it can reveal clues to animal population studies, animal husbandry, different historical animal breeds, and provenance (where the animal or skins originated from). In the case of the Dead Sea Scrolls, DNA testing on the parchment could reveal what type of animal was used and possibly where it came from, providing additional data for questions regarding who wrote the scrolls.
Campana and colleagues analyzed both mitochondrial and autosomal genetic data using stable isotope, genetic, phylogenetic and ion beam analysis. All samples were considered to be well preserved and ideal samples for accurate testing. All but one parchment produced multiple DNA sequences that matched several different species including cow, goat, sheep, and even human. In other words, a parchment assumed to be made from one individual of one species, gave conflicting results as more than one species or more than one individual. Of course it can be assumed the parchment was not made of human skin and therefore human genetic data must have came from handling and processing of the parchment, but parchments can also be contaminated in long-term storage or contact with each other. Testing results can also be skewed by glues and inks or other preparatory treatments used to improve the surface. All of these factors need to be considered when testing truly ancient parchment like the Dead Sea Scrolls.
Previous DNA test results from 2001 and 1996 on the Dead Sea Scrolls produced results pointing to a single species, either ibex (Capra ibex) or domestic goat. While these results may indeed be correct, the likelihood that the results were so exact, when testing such as Campana's and colleagues on better preserved and more recent parchment were so complex, questions the accuracy of the earlier DNA testing. Of course we must not forget, precious artifacts like the Dead Sea Scrolls can not be needlessly dissected to offer unlimited samples for DNA testing labs. But as, Campana states, “Improving our understanding of parchment's DNA content would allow us to develop a predictive model for sampling of historic manuscripts.”
So the messages for today, bravo for the Scientific Method and go see the Dead Sea Scrolls at the Science Museum! Learn the science, archaeology, history and more that surround these amazing artifacts. Ask questions like: did the scroll writers choose ibex for some scrolls over goat because they thought these documents were so special or was ibex as readily available as any other animal species? Did the handling of the scrolls by shepherds who supposedly found them contaminate the actual scroll DNA with sheep, human or goat DNA? What can DNA testing tell us about other ancient artifacts? As long as there are unanswered questions, no matter how small, there will be a need for scientific investigation; which is good news for our future scientists!
Courtesy Wiki Media CommonsScience Buzz bloggers have been buzzing about this topic for some time, but as the time draws near, I thought I would jump in for those new to Science Buzz. The rapidly expanding field of DNA analysis is now being used to verify the genealogy of the great kings of Egypt. Zahi Hawass, chief of the Supreme Council of Antiquities in Egypt, has announced that on February 17th, 2010 he will be revealing the results of DNA testing on the famous mummy of the boy king, Tutankhamun. DNA testing has already been done on King Amenhotep III (who reigned from approximately 1388 to 1351 BCE) for comparison as he is believed to be either Tut’s father or grandfather. The mummy of Amenhotep’s son, Akhenaten (who could be Tut’s father), has yet to be found. Researchers also plan to test the DNA of two mummified fetuses found in the tomb to determine if they are related to Tut and shed light on whether King Tut’s bride, daughter of Akhenaten, was his full sister or half sister.
Despite the popularity of King Tut and the splendid artifacts found in his tomb, he is actually only a minor figure in the history of Egyptian pharaohs, reigning for a mere 10 years in a time of great unrest. The story of Akhenaten is more interesting. Akhenaten, who ruled from 1352 to 1336 BCE, is famous for changing both religion and artistic style in Egypt, what is now known as the Amarna Period. Akhenaton introduced a new monotheistic cult of worship surrounding the sun disc Aten and excluded all other Egyptian gods from being worshipped in an effort to suppress the powerful priesthood of Amun.
Courtesy Hajor and Wiki Media CommonsArtwork during the Amarna Period took on a more naturalistic style and often emphasized affectionate family scenes of the Pharaoh with his wife Nefertiti and their children. Of interest to many art historians is the depiction of Akhenaten himself. He is represented with an accentuated feminine appearance, rounded protruding belly, wide hips, long slender limbs, and a long thin face. Some believe it is a purposeful political depiction stressing his belief in equality of the sexes, some suggest he was a hermaphrodite, and others suggest he had Marfan’s syndrome. People with Marfan’s syndrome are usually very tall with long thin arms and legs, have thin faces, and funnel shaped chests. Unfortunately, until his mummy is located this will remain a mystery.
When Akhenaten died, the priests of Amun regained power, striking Akhenaten’s name from Egyptian records, reversed all of his religious and governmental changes, and returned the capitol to Thebes. His son, Tutankhaten changed his name to Tutankhamun to honor Amun and became the now famous boy king ruling from 1336 to 1327 BCE.
Mr. Hawass has announced plans to test all the royal mummies using their new $5 million DNA lab in the Egyptian museum. However, there is some concern in the scientific field that he will not submit results to labs outside Egypt for independent verification as is common practice in DNA testing. For example, DNA results of Hatshepsut, Egypt’s famous, powerful and only female pharaoh have never been released. Our fascination with the pharaohs is sure to continue for many more centuries.
Courtesy coteIt’s a weird suggestion, I know, because you probably give a lot of thought to whom the various cavemen had sex with anyway, regardless of the weather. But give it a little extra thought today. Because it’s nice out, and the dark corners of your brain could use the sunlight.
So, you guys all know that we aren’t the only human species ever to exist, right? The human family tree had other branches before it got to us (take a look at our Human Spark feature for more on that), and there were times when more than one species lived in the same area, and—in all probability—had interactions with each other. Neanderthals, for instance, lived alongside modern humans for many thousands of years in ice age Europe. Keep in mind, “Neanderthal” isn’t just a synonym for “cave-man.” Neanderthals were a distinct species—they had heavier, longer skulls, and thick, strong bodies. The modern humans of ice age Europe would have looked, more or less, like us. And because the two species were living in the same area for so long, it seems pretty likely that they interacted. But did those interactions include, you know, dinner, dancing, and romantic music?
On one hand, these are sort of fightin’ words. People have suggested that Neanderthals faded into extinction as they interbred with modern humans, but when human DNA was compared with a sequence of Neanderthal DNA, it didn’t look like there was any overlap. That is, if there was any interbreeding, the Neanderthal contributions to our genes have been so diluted with human genes that it doesn’t appear that we have any Neanderthals in our family at all.
On the other hand… Well… I mean… People do all sorts of stuff… We all just want someone to love, right? Or, you know, just think of what a puppy will do to a piece of furniture. And humans and Neanderthals are a lot more similar to each other than puppies and ottomans. Too much? I don’t think so. Look at ligers. Or tigons. Or mules. Similar animals interbreed all the time, but very often they have infertile offspring. And that would explain why we don’t see any Neanderthal genes around today—everybody could have been doing it like it was 2012, but if the offspring couldn’t reproduce it wouldn’t matter to future generations.
Another factor that could explain the lack of genetic overlap (despite Paabo’s certainty of caveman/Neanderthal sexiness) is that our Neanderthal DNA sample just isn’t good enough. Mitochondrial DNA from Neanderthals doesn’t show up in modern humans, and while that’s an incredibly valuable genetic marker, it only makes up a tiny fraction of an organism’s total DNA. The Neanderthal genome hasn’t been completely sequenced yet, and that’s what Paabo means to do. Once we can fully compare the genomes, we can see if the two species became at all mixed.
Because they were definitely doing it.
Courtesy Public domain via WikipediaI recently (and literally) stumbled upon a web page about this remarkable man from the 17th century. His name was Matthias Buchinger, and despite being born without hands, legs or thighs, this guy managed to live a full and amazing life with no less than 4 wives (!?), and fathering something like 11-14 children depending on the source. But even more incredible was how - despite his severe physical deformations - Buchinger was able to rise above Nature’s challenges and become an accomplished musician, inventor, artist, model-in-a-bottle builder, and magician.
Born in Anspach, Germany in 1674, he was the youngest of nine children, and became widely known as “The Little Man from Nuremburg” performing his feats of wonder across much of Great Britain and Europe. Buchinger was only 29 inches tall, and for hands had "two excrescences which grew from his shoulder-blades, like fingers without nails" but his skills in magic, marksmanship, and music were legendary. He played several musical instruments, some of which he invented himself, was accomplished at skittles (bowling), and could dance a hornpipe as well as anyone. He was also a talented calligrapher. His engraving skills are evident by the self-portrait to the right. Hidden within his curls are seven psalms and the Lord’s Prayer written in tiny letters. Buchinger lived much of his adult life in England and Ireland, and performed before King George and many of Europe’s royalty. He died in Cork, Ireland in 1732.
I don’t know about you but I find Buchinger quite inspiring. You can read more about this human marvel in the links below.
Courtesy Joe ShlabotnikFor years now, members of the robust camp of biologists—paleontologists in particular—arguing that birds evolved directly from dinosaurs have kneeled on the thighs and arms of paleontologists who believe that birds did not evolve from dinosaurs, slapped their scrawny bellies pink, and rubbed dirt and grass in their bifocaled faces. And it was only right—the birds from dino people are bigger, and their veiny biceps ripple with the science of a substantial fossil record, while the clammy palms and toast-rack ribcages of the alternate theory paleontologists positively reek of onions and contrary opinions for the sake of argument. It’s only natural.
I mean, we have fossil impressions of feathers on dinosaurs, analogous bones and body-structures in birds and theropod dinosaurs (theropods, again, are two-legged meat-eaters, like T-Rex, velociraptor, etc.), similar bird-dinosaur proteins (take a look at that last link—Liza listed a bunch of other stories in that post)… the list goes on. Some paleontologists pretty much consider birds to be dinosaurs themselves (little dinos that never went extinct). The book is closed. It’s not even fun beating up on those other paleontologists anymore, because… what’s the point? You wouldn’t beat up on a worm, would you?
Ah, but these worms may have gotten their hands on something soft in this fight, and they’re about to give it a twist…
Check it out—like a hammer from nowhere, or sudden and blatant disregard for the no-scratching rule, the birds-didn’t-evolve-from-dinosaurs people have a new weapon, and they’re back on their feet.
Before we go on, I’m just going to emphasize something real quick here: nobody is saying that birds didn’t evolve, or that they didn’t evolve from something very different from birds as we know them. The question is, from what did birds first evolve, and when?
See, the winning theory is that some theropod dinosaurs began getting smaller and more birdlike in the Jurassic period (with a couple interesting exceptions eventually getting bigger and more birdlike later on, but that’s a different story.) These dinosaurs got little, and feathery, and probably started living in trees, and adapted to leaping, gliding, and eventually flying. By the late Jurassic, we have the archaeopteryx, a feathered, toothed, clawed, and bony-tailed flying machine. By the Cretaceous, there are plenty of pretty normal-looking birds around. Easy-peasy, and there are all those fossils I mentioned before.
“Oh yeah?” say the other paleontologists, “Well what about… this?!” And with that, they flick the back of their hand into the crotch of the unsuspecting bird-dino scientists.
“What are you… aaaaaaahh….” They ask.
Birds, say the alternate theory dudes, don’t have the right legs to be descended from dinosaurs. It’s so obvious, even jerks like you should have seen it.
See, birds need to breath lots of air to be able to fly (it’s hard, I’ve tried). To breath more efficiently, birds have air-sacs in addition lungs. Running all over their bodies (even in their bones) the air-sacs help pump lots of air through the birds' respiratory systems. Fossilized bones appear to show the presence of air sacs in some dinosaur species, too, and this has been seen as further evidence for the bird dinosaur link.
The new argument doesn’t dispute that everybody loves air-sacs. It points out that birds can only move their legs in a very limited way, to keep from collapsing some of their air-sacs when they breath. Birds’ femurs (their thigh bones) are largely fixed—when they walk or run, most of the movement comes from their lower legs. All other walking and running animals—including dinosaurs—have moveable thighs.
This difference, some scientists believe, is great enough that fixed-legged birds couldn’t have evolved from moving-legged dinosaurs. They might have evolved alongside dinosaurs, sharing a common ancestor, possibly one of the thecodonts. Thecodonts were dinosaur-like (but definitely not dinosaurs) and they lived during the Triassic period. Some thecodonts evolved into dinosaurs, and the group died off by the end of the Triassic.
“That’s… all?” says mainstream paleontology, straightening up and cracking its knuckles. “Someone is about to get slapped.”
“…Hiss!” say the other guys, squaring their Gollum-like shoulders.
Until I know a little more about the research, I think I have to side with the traditional birds evolved from dinosaurs argument. The alternative theory folks point out that birds are found much earlier in the fossil record than the dinosaurs they are supposed to have evolved from, but it seems to me that that’s more of a problem of overlap than of a gap—couldn’t later bird-like dinosaurs just be the descendants of the dinosaur-to-bird transitional species? It’s not as if anyone thinks that we look at individuals in the fossil record and say, “ok, you evolved from this one, which evolved from this one” etc. If birds didn’t evolved from dinosaurs like the ones we find from the Cretaceous, then we’re left with a huge gap between thecodonts and archaeopteryx and his pals. And it would have to be some pre-dinosaur thecodont, because I feel like the independent evolution of air-sacs, feathers, and everything else in both lines would be a little too much convergent evolution otherwise.
Plus… I’m not clear on why dinosaurs couldn’t have just evolved to have a fixed leg later on, when they needed more efficient respiratory systems for flying. Their mode of locomotion would have necessarily been changing anyway…
Interesting, though, right?
What do y’all think? Is this ridiculous? Or are we too attached to the mainstream model of bird evolution that we’re unable to keep an open mind to new ideas?