The past few weeks have witnessed a spate of remarkable announcements about feathered dinosaurs. First came the story of University of Kansas scientists reconstructing feathers on the four-winged Microraptor to test the gliding abilities of this little dinosaur (1); the authors concluded that Microraptor was fully arboreal, spending it’s lifetime largely in trees, and that avian flight likely evolved from the trees down rather than from the ground up. Next came stunning back-to-back news from two different teams that reconstructed color in the feathers of dinosaurs, giving us our first glimpses of dinosaur coloration (2, 3). Most recently, a study by David Hone and colleagues (4) clearly demonstrates that the feathers of Microraptor attached directly to the bone, as in birds living today, and that the feathers are preserved in life position, rather than being displaced after death, as some have argued.
Together, these announcements got me thinking about the larger meaning of feathered dinosaurs. Beyond the amazing (and seemingly unending) succession of discoveries, most based on exceptionally preserved fossils coming out of China, what larger lessons might we take away from these so-called “dino-birds”? Below I describe my top three. Other paleontologists would undoubtedly come up with different lists, and the items noted here would apply equally well to many non-dinosaurian phenomena. Yet I think that the burgeoning science of feathered dinosaurs admirably underscores each of these points.
1) Never say never.
Scientists like to talk about the limits of science—that is, the limits what’s knowable through scientific investigation. In doing so, we’re prone to make claims like, “Blah-blah-blah [insert topic here] will never be known with any degree of confidence.” Then along comes some bright, skeptical (typically young) investigator who finds a way to probe the supposedly intractable question from a new angle, making those earlier claims seem foolish. This is exactly what happened with dinosaur colors. Limited largely to fragmentary piles of bones and teeth, many paleontologists have lamented that we will never know the colors of dinosaurs. Then it was discovered that fossilized feathers preserved with some Chinese theropod dinosaurs preserve a color-bearing melanin pigment called melanosomes, and that these color-specific cues can be used to reconstruct feather coloration.
Anchiornis is the smallest known dinosaur, about 13 inches long and 100 grams (~4 oz), somewhere between the size of a robin and crow. It was also the animal for which Quanguo Li and colleagues(3) reconstructed coloration over the entire animal. The authors state that “[T]he body was gray and dark and the face had rufous speckles. The crown was rufous, and the long limb feathers were white with distal black spangles.” This claim is astonishing. Just five years ago, few would have imagined that we would ever have the hard data to make such a statement about any dinosaur. And keep in mind that Anchiornis lived more than 150 million years ago!
When it comes to paleontology, many of these surprising insights are possible only because of the application of new technologies. The discovery of dinosaur color depended on the ability of researchers to explore the shape and density of melanosomses in the microstructure of feathers. Similarly, Dave Hone and his colleagues(4) had to examine Microraptor fossils under ultraviolet light to see the detailed interface between bones and feathers.
The lesson here? Feathered dinosaurs teach us to never say never. Questions that appear impenetrable at the moment may well become answerable in the future with the advent of new technologies and new ways of thinking. At the moment, we have no way to determine the skin colors of non-feathered dinosaurs like T. rex or Triceratops. But don’t bet on this staying unknown. History tells us different.
2) Ignorance exceeds knowledge.
There is a major bias among nonscientists that we’ve pretty much figured out all the big stuff about nature. All we’re doing now, people seem to think, is making minor adjustments to our understanding—adding a few more grains of sand to the mountain of knowledge. This myth is perpetuated by school textbooks, which tend to give the implicit impression that the topic under consideration (e.g., biology, chemistry, physics, etc.) can be summarized as an accumulation of facts.
Feathered dinosaurs teach us differently. When I was a kid, dinosaurs were depicted as sluggish, dim-witted, swamp-dwelling, drab-colored behemoths sharing far more in common with Godzilla than with chickens. Thanks largely to the discovery of bird-like dinosaurs, sometimes called “raptors,” this view has been tossed on its head. Almost overnight it seemed, dinosaurs emerged from the swamps as complex, fast-moving, brightly colored creatures with a range of complex behaviors previously unimagined—for example, nest brooding, herding, and burrowing. Feathered dinosaurs showed us that not all of these ancient reptiles were giant; indeed some were no larger than mid-sized birds. To my knowledge, no one in the 1960s pictured little four-winged dinosaurs living in trees.
Science has only scratched the surface of what might be known. To use dinosaurs as an example, more “new” varieties of dinosaurs have been named in the past 25 years than in all prior history, with no signs that the well of discovery is running dry. Similar kinds of statements might be made for virtually all areas of science. Even in disciplines such as physics with a much longer track record than paleontology, ground-breaking, innovative work remains to be done. Science has tended to create artificially walled “silos” around each discipline, walls that today are being torn down. As a result, some of the most exciting work done today occurs at the interfaces of once separate disciplines, often with appropriately hybrid names like “geobiochemistry.” I am excited about 21st Century paleontology, which is becoming increasingly integrated, synthesizing the traditional study of fossils with knowledge and tools from such disparate fields as geochemistry, histology, molecular biology, and paleoclimatology. There’s no question—countless exciting discoveries await talented, hard-working folks with access to as yet unimagined tools. Expect the unexpected.
3) Evolution happens.
Despite the fact that we just celebrated the 150th anniversary of Darwin’s famous treatise on biological evolution, and even though virtually all practicing biologists regard evolution as the abundantly documented centerpiece of their field, only about one half of Americans accept the veracity of this idea. Anti-evolutionists frequently make the claim that we paleontologists have no evidence of intermediate forms in the fossil record. Feathered dinosaurs tell a different story.
When I was a kid, life was a lot simpler. Even kids knew that reptiles (including dinosaurs) had scales and birds had feathers. This naïve categorization has been roundly defeated by not one or two but well over a dozen kinds of dinosaurs with feathers or feather-like structures (but see note below). Indeed the line between dinosaur and bird has blurred to the point that paleontologists frequently describe a new Mesozoic beast as a bird only to have others show that it’s a dinosaur, or vice versa.
Back in the old days (i.e., when I was a kid), biologists often spoke of missing links. In one sense, feathered dinosaurs are exemplary missing links. In another sense, these “dino-birds” underscore the double inaccuracy of the term; missing links are neither missing nor links. Most trivially, intermediate fossil forms are not missing because we’ve found them. More profoundly, they are not links, because evolution rarely follows a simple, ladder progression, with one form evolving into another and so on. Instead, evolution typically branches like a bush, generating not one but numerous lineages that spawn variable numbers of descendents and persist for differing amounts of time. Feathered dinosaurs are an ideal example of this kind of arborescent evolution. Microraptor and Anchiornis are not directly ancestral to modern day birds, but their lineages branched off the dinosaur family tree around the same time as birds did. That’s why they share so many features with living avians, including true feathers.
Dinosaurs aren’t extinct. They fly around above our heads today, charm us with their songs, and adorn our dinner tables. In that sense, all birds are feathered dinosaurs. And they’re not the only well documented example of transitional fossil forms. We have similarly robust evidence for the origin of amphibians, whales, and many other groups—including hominids. Evolutionary biologists need to do an even better job of taking their message public. Evolution happens.
References
1) Alexander, D. E., E. Gong, L. D. Martin, D. A. Burham, and A. R. Falk. 2010. Model tests of gliding with different hindwing configurations in the four-winged dromaeosaurid Microraptor gui. Proceedings of the National Academy of Science. doi: 10.1073/pnas.0911852107.
2) Zhang, F., S. L. Kearns, P. J. Orr, M. J. Benton, Zhou, Z., D. Johnson, Xu. X & Xiaolin W.. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature, doi:10.1038/nature08740.
3) Li, Q., Gao, K.-Q., Vinther, J., Shawkey, M.D., Clarke, J.A., D'Alba, L., Meng, Q., Briggs, D.E.G. and Prum, R.O. "Plumage color patterns of an extinct dinosaur." Science,. doi:10.1126/science.1186290.
4) Hone, D. W. E., H. Tischlinger, Xu X., Zhang, F. 2010. The Extent of the Preserved Feathers on the Four-Winged Dinosaur Microraptor gui under Ultraviolet Light. PLoS ONE, 5(2): e9223. doi:10.1371/journal.pone.0009223.
(Note: One of the hallmarks of science is that every claim always remains open to questioning. Although the vast majority of vertebrate paleontologists now agree that birds are descended from small-bodied feathered dinosaurs, it is worth noting that a small contingent of naysayers remains. Among them is John Ruben of Oregon State University, who has a brand new paper out making this claim. I have not yet read this publication, but think that it is appropriate to mention it here: Ruben, J. 2010. Paleobiology and the Origins of Avian Flight. Proceedings of the National Academy of Sciences, doi:10.1073/pnas.0915099107.)
Together, these announcements got me thinking about the larger meaning of feathered dinosaurs. Beyond the amazing (and seemingly unending) succession of discoveries, most based on exceptionally preserved fossils coming out of China, what larger lessons might we take away from these so-called “dino-birds”? Below I describe my top three. Other paleontologists would undoubtedly come up with different lists, and the items noted here would apply equally well to many non-dinosaurian phenomena. Yet I think that the burgeoning science of feathered dinosaurs admirably underscores each of these points.
1) Never say never.
Scientists like to talk about the limits of science—that is, the limits what’s knowable through scientific investigation. In doing so, we’re prone to make claims like, “Blah-blah-blah [insert topic here] will never be known with any degree of confidence.” Then along comes some bright, skeptical (typically young) investigator who finds a way to probe the supposedly intractable question from a new angle, making those earlier claims seem foolish. This is exactly what happened with dinosaur colors. Limited largely to fragmentary piles of bones and teeth, many paleontologists have lamented that we will never know the colors of dinosaurs. Then it was discovered that fossilized feathers preserved with some Chinese theropod dinosaurs preserve a color-bearing melanin pigment called melanosomes, and that these color-specific cues can be used to reconstruct feather coloration.
Anchiornis is the smallest known dinosaur, about 13 inches long and 100 grams (~4 oz), somewhere between the size of a robin and crow. It was also the animal for which Quanguo Li and colleagues(3) reconstructed coloration over the entire animal. The authors state that “[T]he body was gray and dark and the face had rufous speckles. The crown was rufous, and the long limb feathers were white with distal black spangles.” This claim is astonishing. Just five years ago, few would have imagined that we would ever have the hard data to make such a statement about any dinosaur. And keep in mind that Anchiornis lived more than 150 million years ago!
When it comes to paleontology, many of these surprising insights are possible only because of the application of new technologies. The discovery of dinosaur color depended on the ability of researchers to explore the shape and density of melanosomses in the microstructure of feathers. Similarly, Dave Hone and his colleagues(4) had to examine Microraptor fossils under ultraviolet light to see the detailed interface between bones and feathers.
The lesson here? Feathered dinosaurs teach us to never say never. Questions that appear impenetrable at the moment may well become answerable in the future with the advent of new technologies and new ways of thinking. At the moment, we have no way to determine the skin colors of non-feathered dinosaurs like T. rex or Triceratops. But don’t bet on this staying unknown. History tells us different.
2) Ignorance exceeds knowledge.
There is a major bias among nonscientists that we’ve pretty much figured out all the big stuff about nature. All we’re doing now, people seem to think, is making minor adjustments to our understanding—adding a few more grains of sand to the mountain of knowledge. This myth is perpetuated by school textbooks, which tend to give the implicit impression that the topic under consideration (e.g., biology, chemistry, physics, etc.) can be summarized as an accumulation of facts.
Feathered dinosaurs teach us differently. When I was a kid, dinosaurs were depicted as sluggish, dim-witted, swamp-dwelling, drab-colored behemoths sharing far more in common with Godzilla than with chickens. Thanks largely to the discovery of bird-like dinosaurs, sometimes called “raptors,” this view has been tossed on its head. Almost overnight it seemed, dinosaurs emerged from the swamps as complex, fast-moving, brightly colored creatures with a range of complex behaviors previously unimagined—for example, nest brooding, herding, and burrowing. Feathered dinosaurs showed us that not all of these ancient reptiles were giant; indeed some were no larger than mid-sized birds. To my knowledge, no one in the 1960s pictured little four-winged dinosaurs living in trees.
Science has only scratched the surface of what might be known. To use dinosaurs as an example, more “new” varieties of dinosaurs have been named in the past 25 years than in all prior history, with no signs that the well of discovery is running dry. Similar kinds of statements might be made for virtually all areas of science. Even in disciplines such as physics with a much longer track record than paleontology, ground-breaking, innovative work remains to be done. Science has tended to create artificially walled “silos” around each discipline, walls that today are being torn down. As a result, some of the most exciting work done today occurs at the interfaces of once separate disciplines, often with appropriately hybrid names like “geobiochemistry.” I am excited about 21st Century paleontology, which is becoming increasingly integrated, synthesizing the traditional study of fossils with knowledge and tools from such disparate fields as geochemistry, histology, molecular biology, and paleoclimatology. There’s no question—countless exciting discoveries await talented, hard-working folks with access to as yet unimagined tools. Expect the unexpected.
3) Evolution happens.
Despite the fact that we just celebrated the 150th anniversary of Darwin’s famous treatise on biological evolution, and even though virtually all practicing biologists regard evolution as the abundantly documented centerpiece of their field, only about one half of Americans accept the veracity of this idea. Anti-evolutionists frequently make the claim that we paleontologists have no evidence of intermediate forms in the fossil record. Feathered dinosaurs tell a different story.
When I was a kid, life was a lot simpler. Even kids knew that reptiles (including dinosaurs) had scales and birds had feathers. This naïve categorization has been roundly defeated by not one or two but well over a dozen kinds of dinosaurs with feathers or feather-like structures (but see note below). Indeed the line between dinosaur and bird has blurred to the point that paleontologists frequently describe a new Mesozoic beast as a bird only to have others show that it’s a dinosaur, or vice versa.
Back in the old days (i.e., when I was a kid), biologists often spoke of missing links. In one sense, feathered dinosaurs are exemplary missing links. In another sense, these “dino-birds” underscore the double inaccuracy of the term; missing links are neither missing nor links. Most trivially, intermediate fossil forms are not missing because we’ve found them. More profoundly, they are not links, because evolution rarely follows a simple, ladder progression, with one form evolving into another and so on. Instead, evolution typically branches like a bush, generating not one but numerous lineages that spawn variable numbers of descendents and persist for differing amounts of time. Feathered dinosaurs are an ideal example of this kind of arborescent evolution. Microraptor and Anchiornis are not directly ancestral to modern day birds, but their lineages branched off the dinosaur family tree around the same time as birds did. That’s why they share so many features with living avians, including true feathers.
Dinosaurs aren’t extinct. They fly around above our heads today, charm us with their songs, and adorn our dinner tables. In that sense, all birds are feathered dinosaurs. And they’re not the only well documented example of transitional fossil forms. We have similarly robust evidence for the origin of amphibians, whales, and many other groups—including hominids. Evolutionary biologists need to do an even better job of taking their message public. Evolution happens.
References
1) Alexander, D. E., E. Gong, L. D. Martin, D. A. Burham, and A. R. Falk. 2010. Model tests of gliding with different hindwing configurations in the four-winged dromaeosaurid Microraptor gui. Proceedings of the National Academy of Science. doi: 10.1073/pnas.0911852107.
2) Zhang, F., S. L. Kearns, P. J. Orr, M. J. Benton, Zhou, Z., D. Johnson, Xu. X & Xiaolin W.. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature, doi:10.1038/nature08740.
3) Li, Q., Gao, K.-Q., Vinther, J., Shawkey, M.D., Clarke, J.A., D'Alba, L., Meng, Q., Briggs, D.E.G. and Prum, R.O. "Plumage color patterns of an extinct dinosaur." Science,. doi:10.1126/science.1186290.
4) Hone, D. W. E., H. Tischlinger, Xu X., Zhang, F. 2010. The Extent of the Preserved Feathers on the Four-Winged Dinosaur Microraptor gui under Ultraviolet Light. PLoS ONE, 5(2): e9223. doi:10.1371/journal.pone.0009223.
(Note: One of the hallmarks of science is that every claim always remains open to questioning. Although the vast majority of vertebrate paleontologists now agree that birds are descended from small-bodied feathered dinosaurs, it is worth noting that a small contingent of naysayers remains. Among them is John Ruben of Oregon State University, who has a brand new paper out making this claim. I have not yet read this publication, but think that it is appropriate to mention it here: Ruben, J. 2010. Paleobiology and the Origins of Avian Flight. Proceedings of the National Academy of Sciences, doi:10.1073/pnas.0915099107.)