Why I Believe Bill Nye Should Not Debate Creationism

If you are not already aware, Bill Nye (the Science Guy) and Ken Ham (founder of the Creation Museum) are scheduled to have a debate at the Creation Museum on February 4, 2014.

This debate was apparently triggered by a video posted by Bill Nye entitled, “Creationism is Not Appropriate For Children” on YouTube.  Not to be undone, Ken Ham posted his own response with embedded links to two other Ph.D.s who amplify his belief that evolution, not Creationism, is damaging to children.

If the goal is science education, then I believe this debate is a poor way to improve the reception of science education in the general public.  Why do I feel this way?

There is a poor or nebulous definition of evolution and science by both parties.

In his video, Bill Nye states, “Evolution is the fundamental idea in all of biology.”  I really like Bill Nye, but I’m sorry, Bill.  Evolution is not an idea.  It is a scientific theory.  If you’re going to have a debate about science, definitions become hugely important.  A scientific theory is a testable, falsifiable, and predictable explanation of natural phenomena.  If you couch evolution as an idea, you open the door to a debate about ideology, not science.

Of course, Ken Ham has science wrong as well. He says, “Science means knowledge – you can divide science into historical science … and observational science.”  No on both fronts.  First, science as it is practiced is not a definition but a method — specifically methodological naturalism.  It is the tool by which we understand the natural world — a narrow discipline, in fact, that seeks to pose answerable questions about nature.  Second, science is science.  All science is based on observations at some level — the dinosaur bones may not “come with labels on them,” but they are observable data that can measured, studied, and so forth.  So, there is not observable versus historical science — it’s all the same thing.

A scientist works under a theory, an explanation for some type of phenomenon in the natural world, to test hypotheses.  If you work on chemistry, you are working under (among other theories) the atomic theory which states that all matter is made of atoms with specific properties.  Until recently, chemists have done a bang up job of testing and predicting chemical reactions and their consequences without seeing directly into atoms.  That’s because the testable explanation (atomic theory) was effective for inferring what should occur.  So, to say that evolution is “historical science” which is “beliefs about the past” is a gross misconstruction of how science works.

When Ken Ham says, “If evolution were true … it would be so obvious to the kids …” he is ignoring the fact that many applicable theories of science are weird and not obvious.  For example, the theories of general and special relativity predict that time is experienced differently by different objects at different speeds and in different gravitational fields.  If you use satellite technology, those satellites whizzing in orbit around the earth have clocks that quickly go out of synch with those on earth (which is explained by the theories of relativity) and thus we have to take special measures to synchronize them with our devices on the earth (GPS comes to mind).  That is good science but not something particularly obvious to kids.

In a nutshell, science is like the honey badger of internet lore — it doesn’t care about your beliefs or opinions.  Data drives what is accepted and rejected.

We are again fighting a metaphysical clash of civilizations.

Based both on what Bill Nye and Ken Ham say, this debate is not about data.  A scientific debate would be about data.  Instead, we have what amounts to, in my mind, another metaphysical clash of civilizations.  Ken Ham and his organization are very clear on this.  He is not concerned about data, but rather showing that “Creationism teaches children that they’re special, that they’re made in the image of God.”  In that one statement, you have what is actually being debated spelled out: whether or not you believe in a particular deity in a particular way.  This is why Ken Ham, his organizations, and others like him make the leap from teaching evolution to teaching kids they’re “just animals” to gay marriage and so forth.

However, Bill Nye is not doing anyone a favor by saying, “In a couple of centuries that world view [creationism] will not exist … there’s no evidence for it.”  Nye has basically indicated that, yes, evolution is a world view, but it is supported by evidence.  And if that is true, then it follows that in this metaphysical clash of civilizations you have to pick a side.  At least, if you follow Ken Ham and his compatriots, that is likely what you are led to believe from such statements.

There is No Clear Distinction About Faith and Creationism

I have said this before, but it bears repeating – there is no conflict between science and faith.  Yet, that is precisely what this debate is already boiling down to.  Science is not faith – it is a tool for understanding the natural world.  Faith is a deeply personal set of beliefs that often cannot be demonstrated scientifically, but that makes them no less valid to the individuals that hold them.  This is not my idea, not by a long shot, but to rephrase the words of many who have come before me, science and faith are after separate goals.  You don’t scientifically test faith, and you don’t apply faith where science works well (the natural world).  This is why they can and should coexist — they serve different purposes, often to the betterment of us all by people with noble intentions.

But the Creationism of Ken Ham and the Creation Museum is not mainstream Christianity.  Many Christians from many faith traditions accept science and evolutionary theory while maintaining their faith.  Ken Ham wants you to conflate his narrow concept of Christianity (a fundamental, literal interpretation of a particular version of the Bible) with Christianity as it actually exists in the world.  But that conflation works to his advantage, because if we are choosing camps, and you identify as a Christian, you cannot “believe” evolution because a humanist (whatever that may mean to you), Bill Nye, is coming after your faith.

A Plea and Some Thoughts

No one person holds all the keys to our problems, so I would never be so bold as to say I have the answer.  Here, then, is my plea and a few thoughts.

I think what many scientists, myself included, are troubled by is hucksterism and charlatanism — snake oil salesmen dressed in religious or authoritarian garb using ignorance to fund their own ambitions and power.  But it is vitally important that we do not conflate that clear and present danger with faith overall.  Given that a majority of Americans identify as people of faith, broadly lumping them in with extremists serves no one and is very damaging.  My plea to my scientific colleagues is, stop doing that.  This is just as damaging as saying that people with no religious beliefs are evil, wrong-headed, and trying to subvert American culture.

As I have said before, fear, not data, is the bottom line here.  People are afraid that their faith is being attacked — once you are afraid, data (the currency of scientists) doesn’t really matter.  What scares people about science?  What scares them about evolution?  How, as scientists, do we work with the majority of people who can see the benefits of science as a tool but are afraid to compromise their spirituality?  That, to me, is the challenge of our time.

You will not convince those with extreme convictions to self-reflect and re-evaluate.  You can bring oceans of data and heaps of observations, but it will do you no good, because the debate is not really about science but about fear and emotion.  So, if Ken Ham and his followers are convinced they are right, having a debate only ever further convinces them that they are.  Do you really think Ken Ham would ever take the results of the debate as anything but a win if not just great publicity?

My last thought or plea: don’t debate Ken Ham and other so-called Creationists.  There are people convinced to their core that the world is flat – no amount of data and debate will sway them, and nothing much will be accomplished.  But they, like Ken Ham, do not represent the majority.  The majority is who we desperately need to reach.  Certainly, when such extremist views threaten to undermine science education, we should and must push back as the National Center for Science Education has admirably done.  That is very different, however, from going out of one’s way to have what will amount mostly to spectacle and the reinforcing of deeply held convictions on both sides.

Again, I like and respect Bill Nye a lot, and I think he has done wonders for science education in the United States. To Bill Nye and any other well-meaning scientists out there who want to improve science education, please do not debate Creationists — this is not the way to accomplish what we all want.

What lies beneath the cartilage just might help you become a giant dinosaur

Figure 7 from our PLOS ONE paper -- This figure conveys the essence of our conclusions: as mammals become giants, their joints become ever more congruent with thinning articular cartilage.  For dinosaurs, the cartilage remains thick and the joint region expands.

You can read the paper for free by clicking here.

As I recently learned from a fall in which I broke one of my ribs, gravity is an irresistible force.

My poor broken rib.

My poor broken rib.

Gravity’s relentless pull has shaped the evolution of the skeleton in land vertebrates who have had to stand tall or be crushed.  Trees have it easy in that they only have to stand and sway (Vogel, 2003) – our skeletons have to resist gravity while on the move (McGowan, 1999; Carter and Beaupré, 2001).  If force equals mass times acceleration, then every time you walk, jog, or climb a flight of stairs, you are pummeling your limb skeleton with forces greater than your body weight!  But your bones are alive and they adapt to this daily abuse by changing their shapes to best resist those forces.  Therefore, paleontologists, like my colleagues and I, are obsessed with bone shape because it is a proxy record of how the limb skeleton adapted to support and move a fossil animal like a dinosaur.  Until we recreate living dinosaurs ala Jurassic Park, limb shape is the next best thing to putting a dinosaur or mastodon on a treadmill.

Many dinosaurs were successful in becoming land giants, whereas a comparative handful of land mammals have ever crossed the 1,000 kg mark (Farlow et al., 1995, 2010; Prothero and Schoch, 2002; Prothero, 2013).

The average dinosaur (excluding birds) weighed in at over 1 ton, whereas the average land mammal barely tips the scales at 1 kilogram. (c) 2013 M.F. Bonnan.

The average dinosaur (excluding birds) weighed in at over 1 ton, whereas the average land mammal barely tips the scales at 1 kilogram. (c) 2013 M.F. Bonnan.

Therefore, you might predict to see stark differences in limb skeleton shape between dinosaurs and land mammals … and yet you don’t!  In fact, getting big on land as a dinosaur or mammal usually results in stout columnar limb bones which resist weight combined with a decrease in activities like running or jumping (Christiansen, 1997, 2007; Carrano, 2001; Biewener, 2005; Bonnan, 2007).  In essence, you get an interesting but ultimately boring pattern that shows us there are only so many solutions to fighting gravity.

In a recently published open-access, peer-reviewed article in PLOS ONE, my colleagues and I have shown that there is one area of a limb bone that does change in different ways with increasing size between land mammals and dinosaurs: the joint-bearing region.

By Bonnan after Carter & Beaupre (2001) and Holliday et al. (2010).

Dinosaurs share the primitive tetrapod condition of retaining thick cartilaginous joints.  Diagram by Bonnan after Carter & Beaupre (2001) and Holliday et al. (2010).

Called the sub-articular surface, this zone supports the slippery and pliable articular cartilage that makes movement possible at joints by decreasing friction and absorbing stress.  We focused on this region because: 1) its shape should reflect how the bone beneath the cartilage was reacting to stress; and 2) recent work has shown that articular cartilage thickness in dinosaurs and land mammals differs, being very thick (several centimeters in some cases) in the former and very thin (only a few millimeters) in the latter (Graf et al., 1993; Egger et al., 2008; Bonnan et al., 2010; Holliday et al., 2010; Malda et al., 2013).

What we found surprised us.  As land mammals become giants, their sub-articular regions become narrow with well-defined surface features.  In contrast, becoming a giant sauropod involves an increase in the sub-articular region combined with a subdued, gently convex profile.

Figure 3 from our PLOS ONE paper -- On the X-axis, the sub-articular bone region narrows significantly with increasing size, and the shapes of these regions become more convex and/or distinct.

Figure 3 from our PLOS ONE paper — On the X-axis, the sub-articular bone region narrows significantly with increasing size, and the shapes of these regions become more convex and/or distinct.

Figure 5 of our PLOS ONE paper -- .  In particular, the sub-articular region expands tremendously whereas its overall shape remains gently convex.

Figure 5 of our PLOS ONE paper — . Along the X-axis, the sub-articular region of the humerus expands tremendously whereas its overall shape remains gently convex.

Why this difference?  Our results suggest two interrelated relationships.  First, sub-articular bone profile and cartilage thickness go hand-in-hand.  In living animals, those with thick articular cartilage (alligators and guinea fowl birds in our sample) have expanded sub-articular regions with gentle convexity, whereas those with thin articular cartilage (the living mammals in our sample) retain narrow and increasingly well-defined sub-articular regions.  Hence, seeing the narrow and well-developed sub-articular regions in fossil elephants and Paraceratherium show convincingly that they had very thin articular cartilage.  In contrast, the expanded and gently convex ends of the limb bones in sauropods appear to be well-correlated with thick articular cartilage.

Second, and more intriguing, these differences suggest different adaptations to becoming a giant constrained by cartilage thickness.  In mammals, it has been well-documented that the best way to disperse stress through thin cartilage is to increase the surface contact area (Simon et al., 1973; Egger et al., 2008).  In other words, mammals spread the load by narrowing their joints and increasing surface complexity, allowing the bones to articulate closely.  As we say in the paper, becoming a giant mammal means developing highly congruent joints.  In contrast, becoming a giant sauropod dinosaur involves retaining thick articular cartilage that presumably deforms under pressure.  This would go a long way to explaining the expanded sub-articular surfaces we see in sauropods: deforming a thick block of cartilage safely likely requires enough space over which to spread the load.

What does this all have to do with the frequency of gigantism?  We speculate that articular cartilage thickness may have a limiting effect on size.  If in mammals the best way to spread stress through a joint is by thinning the cartilage and increasing congruence, you are going to get to a point where the joints are as congruent as possible and the cartilage cannot get any thinner.  In contrast, retaining thick articular cartilage at large size might have been one factor that contributed to the frequent evolution of so many dinosaur giants.  Therefore, our data suggest that the rarity of large land mammals may be due, in part, to their highly congruent limb joints with thin articular cartilage, whereas the success of sauropod dinosaurs as giants may be tied, in part, to their retention of thick articular cartilage.

Figure 7 from our PLOS ONE paper -- This figure conveys the essence of our conclusions: as mammals become giants, their joints become ever more congruent with thinning articular cartilage.  For dinosaurs, the cartilage remains thick and the joint region expands.

Figure 7 from our PLOS ONE paper — This figure conveys the essence of our conclusions: as mammals become giants, their joints become ever more congruent with thinning articular cartilage. For dinosaurs, the cartilage remains thick and the joint region expands.

As we say in the article, we in no way intend this to be the last word on dinosaur gigantism or imply that this was the only explanation for their success as land giants.  In fact, we hope our work, which was limited to 2-D profiles of the sub-articular surfaces, will be expanded upon using newer, 3-D technology by future researchers (see for example recent work by Tsai and Holliday [2012]).  So the next time you take a walk, think about and appreciate how a narrow slice of cartilage helps ensure your bones glide past one another and don’t smack together.  I only wish thick, pliable cartilage was in my poor rib, which deformed and snapped under stresses far, far less than those which pummeled the limbs of giant mammals and dinosaurs.

My poor broken rib revisited.

My poor broken rib revisited.

You can read the paper, for free, here.

My Co-authors

This study would not have been published without the help and perseverance of my co-authors.

RayWRay Wilhite is a kindred sauropod spirit, and an associate professor of veterinary anatomy at Auburn College who knows far more about alligator anatomy than I can ever hope to amass.  His assistance in helping me twice procure, dissect, and prepare alligators from the Louisiana Rockefeller Wildlife Refuge was invaluable.  He also introduced me to Ruth Elsey, the goddess of alligators, whom ended up as an author on one of our previous forays into the relationship between cartilage thickness and shape (Bonnan et al., 2010).

Ray comments on our paper: “For most of the history of vertebrate paleontology scientists and explorers focused on finding new fossils and organizing them into meaningful taxonomic groups.  Recently, however, many paleontologists have shifted their focus to trying to understand the biology and functional morphology of extinct species.  I believe our study has moved the discussion forward regarding the morphological adaptations of sauropods that allowed the to grow to such gigantic proportions.  Our study provides a possible clue about why sauropod humeri and femora have expanded ends and large terrestrial mammals do not.  The revelation in recent years that there is most likely a significant portion of the articular surface missing in preserved sauropod limb bones is supported by this study.  Slowly but surely we are beginning to not just put flesh on the bones, but put the bones on the bones and see what lay between.”

Simon L. Masters was a former graduate student of mine, and his thesis on the ontogeny of the forelimb in Allosaurus was to SimonMform the basis of the theropod dinosaur set in our paper.  Simon, along with Jim Farlow, previously helped with the writing and analysis of using shape-based statistics for determining sex from the alligator femur (Bonnan et al., 2008).  Simon has done well for himself and I’m happy to say he is inspiring a new crop of STEM students as a high school teacher at the all-girls Beaumont School in Cleveland Heights, Ohio.

AdamYAdam M. Yates has been an invaluable friend and colleague, and his contribution to this paper allowed us to compile a great deal of morphometric data on “prosauropods.”  More specifically, when he, Johann Neveling, and I were working up a different paper on what would become our new dinosaur, Arcusaurus (Yates et al., 2011), I began running morphometric analyses of the distal ends of dinosaur and archosaur humeri because we had only the distal end of that animal’s humerus.  That figure never made the final paper but it was my first hint that something interesting was going on in dinosaurs: as I plotted “prosauropod” and sauropod humeri, I could see that there was this trend towards expansion and slight convexity.  I wanted to note that in our Arcusaurus paper, but Adam encouraged me to save the data for a later time … and that time is now.

ChristineGChristine Gardner was one of my many successful undergraduate honors students.  While working with me, she measured nearly all of the Afrotherian mammals in our paper for her undergraduate thesis on long bone scaling in these mammals.  Her hard work at collecting and analyzing her dataset not only gave her honors in finishing her undergraduate work, but contributed in a substantial way to our paper.  She has also journeyed with me out to the field a number of times, and has successfully landed herself in the graduate program at the South Dakota School of Mines.

Christine had this to say about our study: “It was the summer between my junior and senior years when I officially began my undergraduate thesis project. Obviously a new experience for me, I didn’t entirely know what to expect. Little did I know I’d watch my raw data not only yield my honors thesis, but eventually become part of much bigger research which has ended with my name being published. Not many students get to share this privilege before finishing their Master’s thesis.”

AdamAAdam Aguiar is one of my new colleagues at the Richard Stockton College of New Jersey who specializes is understanding the molecular-level details of bone and cartilage biology.  After the first draft of the paper, he was invaluable at providing insight into thinking about articular cartilage and its responses to shock and stress.  This gave the paper a new lease on life, and I doubt we would have been successful on our next submission had it not been for his encouragement and contribution.

Acknowledgments

We thank the many institutions and individuals that provided us with access to specimens for this study.  I cannot possibly list all of them here: much of the archosaur data was collected for previous studies (Bonnan, 2004, 2007; Bonnan et al., 2008, 2010)  and the heartfelt thanks and appreciation expressed in those references continues more strongly than ever here.  For the present study, we wish to thank the following institutions and staff: AMNH: N. B. Simmons and staff (Mammalogy), J. Meng, J. Galkin, and staff (Fossil Mammals); FMNH: W. Stanley and staff (Mammalogy), K. D. Angielczyk, W. Simpson, and staff (Fossil Mammals); UNMH: R. Irmis, M. Getty, and staff; CLQ: M. Leschin; SAM: A. Chinsamy-Turan and staff; BPI: B. Rubidge and staff.  We thank Kimberley Schuenman at WIU for collecting data on felids used in this study.  Feedback from Gregory S. Paul, Henry Tsai, and Stephen Gatesy at the 2012 Society of Vertebrate Paleontology meeting further improved our manuscript.  Discussions with Jason Shulman at the Richard Stockton College of New Jersey on static physics were helpful.  Donald Henderson and an anonymous reviewer provided useful comments, critiques, and suggestions on a first draft of this manuscript.  We are also indebted to PLOS ONE editor Peter Dodson for shepherding our manuscript through the PLoS system, and his feedback, comments, and suggestions.

Last but not least – a great big thank you to my new employer, the Richard Stockton College of New Jersey, for helping with publication costs!  Thank you Stockton and the Grants Office, particularly Beth Olsen!

 An Important Aside on Methods and Why We Did What We Did

  • We chose to focus on evolutionary lines of mammals and dinosaurs that gave rise to the very largest land species.  For mammals, we focused on the placental (eutherian) lines called Afrotheria and Laurasiatheria because elephants and Paraceratherium, the giant rhino relative, descended from these.  For dinosaurs, we focused on the Saurischians because the giant, long-necked “brontosaurs” called sauropods were members. We also selected smaller-bodied relatives of these giants in their family trees to examine how similar or different the sub-articular zones of these giants were to their smaller relatives.  To analyze shape, we used a computer program called Thin-Plate Splines that tracks and compares landmark coordinates on bones.
  • Because bony landmarks and sub-articular surfaces were not always anatomically homologous between archosaurs and mammals, we avoided issues of mixing non-homologous areas in our data by running the analyses on these two groups separately.
  • Why did we use a two-dimensional analysis instead of a three-dimensional analysis?  Undoubtedly, three-dimensional shape analysis would have further enhanced our interpretation of sub-articular shape patterns.  However, a number of challenges prevented such an approach:
    • First and most significantly, the data collected in this study span a period of over 10 years during which time cost-effective and portable three-dimensional scanning technologies for acquiring large bone geometries have only recently started to become available.  Had we access to these technologies ten years prior, we would have utilized them, as we plan to utilize such approaches in future studies.
    • Second, our main goal in this study was to quantify whether or not there were significant differences in the scaling patterns of surface morphology between eutherian mammal and saurischian dinosaur long bones, and whether such differences were correlated with known differences in articular cartilage properties.  We emphasize that our goal was not to realistically recreate joint surfaces or establish precise measures of joint articulation, nor do we propose how the three-dimensional shape of the subchondral bone is used to reconstruct joint geometry.  Our selection of the humerus and femur furthers our goal: these are long bones in which a significant portion of the subarticular surfaces can be reliably captured and interpreted in two dimensions.
    • Finally, third, two-dimensional data is valuable, comparable to previous studies, and provides a good first-level approximation of scaling patterns.  Just as linear morphometrics informed and directed the study of two-dimensional geometric morphometrics (GM) of long bones, so, too, can two-dimensional GM illuminate where future three-dimensional GM studies can make the best impact.  Our study is certainly not the last word on long-bone scaling and subarticular patterns in non-avian dinosaurs.  Rather, we hope it inspires and provides the basis for research incorporating three-dimensional technologies in years to come.

References

Biewener, A. A. 2005. Biomechanical consequences of scaling. The Journal of Experimental Biology 208:1665–76.

Bonnan, M. F. 2004. Morphometric analysis of humerus and femur shape in Morrison sauropods: implications for functional morphology and paleobiology. Paleobiology 30:444–470.

Bonnan, M. F. 2007. Linear and geometric morphometric analysis of long bone scaling patterns in Jurassic neosauropod dinosaurs: their functional and paleobiological implications. Anatomical Record (Hoboken, N.J. : 2007) 290:1089–111.

Bonnan, M. F., J. O. Farlow, and S. L. Masters. 2008. Using linear and geometric morphometrics to detect intraspecific variability and sexual dimorphism in femoral shape in Alligator mississippiensis and its implications for sexing fossil archosaurs. Journal of Vertebrate Paleontology 28:422–431.

Bonnan, M. F., J. L. Sandrik, T. Nishiwaki, D. R. Wilhite, R. M. Elsey, and C. Vittore. 2010. Calcified cartilage shape in archosaur long bones reflects overlying joint shape in stress-bearing elements: Implications for nonavian dinosaur locomotion. Anatomical Record (Hoboken, N.J. : 2007) 293:2044–55.

Carrano, M. T. 2001. Implications of limb bone scaling, curvature and eccentricity in mammals and non-avian dinosaurs. Journal of Zoology 254:41–55.

Carter, D. R., and G. S. Beaupré. 2001. Skeletal Function and Form : Mechanobiology of Skeletal Development, Aging, and Regeneration. Cambridge University Press, Cambridge; New York, pp.

Christiansen, P. 1997. Sauropod locomotion. Gaia 14:45–75.

Christiansen, P. 2007. Long bone geometry in columnar-limbed animals: allometry of the proboscidean appendicular skeleton. Zoological Journal of the Linnean Society 149:423–436.

Egger, G. F., K. Witter, G. Weissengruber, and G. Forstenpointner. 2008. Articular cartilage in the knee joint of the African elephant, Loxodonta africana, Blumenbach 1797. Journal of Morphology 269:118–127.

Farlow, J., P. Dodson, and A. Chinsamy. 1995. Dinosaur biology. Annual Review of Ecology and \ldots 193:44.

Farlow, J., I. D. Coroian, and J. Foster. 2010. Giants on the landscape: modelling the abundance of megaherbivorous dinosaurs of the Morrison Formation (Late Jurassic, western USA). Historical Biology 22:403–429.

Graf, J., E. Stofft, U. Freese, and F. U. Niethard. 1993. The ultrastructure of articular cartilage of the chicken’s knee joint. Internationl Orthopaedics (SICOT) 17:113–119.

Holliday, C. M., R. C. Ridgely, J. C. Sedlmayr, and L. M. Witmer. 2010. Cartilaginous Epiphyses in Extant Archosaurs and Their Implications for Reconstructing Limb Function in Dinosaurs. PLoS ONE 5:e13120.

Malda, J., J. C. de Grauw, K. E. M. Benders, M. J. L. Kik, C. H. A. van de Lest, L. B. Creemers, W. J. A. Dhert, and P. R. van Weeren. 2013. Of Mice, Men and Elephants: The Relation between Articular Cartilage Thickness and Body Mass. PLoS ONE 8:e57683.

McGowan, C. 1999. A Practical Guide to Vertebrate Mechanics. Cambridge University Press, New York, 316 pp.

Prothero, D. R. 2013. Rhinoceros Giants: The Paleobiology of Indricotheres. Indiana University Press, Bloomington, IN, 160 pp.

Prothero, D., and R. Schoch. 2002. Horns, Tusks, and Flippers: The Evolution of Hoofed Mammals. Johns Hopkins University Press, Baltimore, 315 pp.

Simon, W. H., S. Friedenberg, and S. Richardson. 1973. Joint congruence: a correlation of joint congruence and thickness of articular cartilage in dogs. The Journal of Bone and Joint Surgery (American) 55:1614–1620.

Tsai, H., and C. M. Holliday. 2012. Anatomy of archosaur pelvic soft tissues and its significance for interpreting hindlimb function. Journal of Vertebrate Paleontology Program and Abstracts:184.

Vogel, S. 2003. Comparative Biomechanics: Life’s Physical World. Princeton University Press, 580 pp.

Yates, A. M., M. F. Bonnan, and J. Neveling. 2011. A new basal sauropodomorph dinosaur from the Early Jurassic of South Africa. Journal of Vertebrate Paleontology 31:610–625.

The NAMS Research Symposium — a Stockton Success!

On behalf of Tara Luke and myself, a huge thank you to everyone at Stockton for helping to make this year’s NAMS Symposium such a success!

Please thank all of your students for doing such an excellent job.

Also, thank you to Dean Weiss, to Tana Tracey who helped set up the food services and location before she retired, thanks to David Dimmerman and all in A&S who helped with printing the volumes of posters, and of course the judges: Jason Shulman, Eva Baranowski, Mark Sullivan, Russ Mason, Dick Colby, and Adam Aguiar.  And, last but not least, thanks to Provost Harvey Kesselman for attending the event and offering such great words of encouragement to our students.

Pictures of the winners and the event can been seen by clicking here.

Complete with feathers

Despite the opening scene in the movie Jurassic Park where a team of paleontologists and their field hands sweep dirt (which looked like kitty litter) off a completely articulated “Velociraptor,” it is actually quite rare to get anything even remotely complete and articulated from the fossil record.  We paleontologists are often ecstatic if we get over 50% of a skeleton, and the higher that number creeps, the bigger our grins get.  As someone who has had the good fortune to find and name two dinosaurs, believe me — even a 40% complete skeleton is enough to throw a party about.  And that’s just if the skeleton is in pieces, let alone articulated in any semblance.

Hence the eternal question, “how do you really know what you have?  Aren’t you just speculating?”  The answer to that question involves cars and trip to the junkyard.  If you were an expert on automobiles, and you went to a junkyard and found bits and pieces of cars, you could still have some very good approximations of what was in the scrap heap.  You might, from pieces of engine block and chassis undergirding, be able to get down to the make or model, and even have a fair idea of how large the car was.  So it is with dinosaur skeletons.  Many of us know our anatomy well, and so even if the whole animal isn’t there, we can often say a lot, factually, about what was probably or almost certainly there.

Therefore, when we do find a complete or nearly complete dinosaur, it is truly rare and mind-blowing.  Such is the case with the newly discovered predatory dinosaur, Sciurumimus albersdoerferi, reported in the journal PNAS by Oliver Rauhut and colleagues.  The genus name, by the way, essentially translates to “squirrel mimic.”  This little, post-hatchling dinosaur was discovered in the same Late Jurassic sediments from Germany as its more famous feathered relative, Archaeopteryx.  This animal is complete, and I do mean complete.  To put this in the proper perspective, bear in mind that the delicate bones of the hands and feet and nearly every single tail (caudal) vertebra, elements that are normally lost to time, are preserved.  In fact, even the hyoid bone, the splint-like tongue-anchoring bone in all jawed vertebrates, is present, tucked just behind and beneath the chin.

This little predator is not on the line of dinosaurs that led to the birds (birds are dinosaurs?).  Instead it belongs to a family of predatory dinosaurs called megalosauroids that share more deeper, distant common ancestors with the coelurosaur line that led to birds.  And here’s where things get truly weird: this little predator had filamentous proto-feathers preserved at the base of its tail and along parts of its body.  Given the position of this predatory dinosaur in the family tree, it strongly suggests that all or nearly all predatory dinosaurs had some kind of feathers, proto-feathers, or filamentous structures adorning their bodies.  And here again, we have an animal with no hope of flying (the arms are much too small to have been effective wings) still sporting plumage or its equivalent.

With hindsight, we might now say that not only was Jurassic Park a bit off the mark with how it portrayed dinosaur discoveries, but it was also, perhaps, too conservative with its predatory dinosaurs, who might have sported filaments and feathers.  Perhaps this is something Steven Spielberg and friends could fix with the magic of CG when Jurassic Park is re-released on some future date in ultra hi-def surround holographic discs that do not yet exist.  Until then, you could always watch the parts with Velociraptor through a feather duster.

Stop-and-go mammals and “warm-blooded” dinosaurs

Ever since Thomas Huxley opined that dinosaurs and birds might be related, a debate has waxed and waned over whether dinosaurs were simply inflated, “cold-blooded” reptiles or active, “warm-blooded” creatures.  Tied into these metabolic “states” have been judgement calls as well: we mammals tend to have warmer feelings for endotherms than for ectotherms (pun very much intended).

Our best data for inferring dinosaur physiology comes to from studies of the microscopic structure of long bones in thin cross-sections, a science called histology.  Bone is a dynamic, living tissue that provides a record of the relative speed at which its tissues were laid down during growth and development.  Bone growth and development rely on a good blood supply, and in a typical long bone cross-section, one can see the conduits that once carried life-sustaining blood vessels.  These circular rings of bone are called Haversian canals.

The rate or speed at which bone tissues are laid down effects how they look in cross-section, an observation first made by the famous Italian researcher Amprino and known as Amprino’s Law.  When bone grows slowly, fewer blood vessels are necessary to sustain the growth, and consequently there are few Haversian canals.  In contrast, when bones grows quickly, many blood vessels are needed to supply fuel for the growth, and therefore Haversian canals abound.  Additionally, slow-growing bone has time to lay itself down in nice, concentric layers like the rings of a tree.  This type of bone is called lamellar because of its distinctive layering.  In contrast, fibrolamellar bone occurs when bone is being laid down quickly — somewhat like a mason throwing together a wall of bricks as fast as possible and in no particular order.  In other words, fibrolamellar bone can look a mess compared with lamellar bone.

Ectothermic vertebrates like an alligator tend to have lamellar bone with few Haversian canals, whereas endotherms such as a bird will show fibrolamellar bone pocked with many Haversian canals.  But there’s a wrinkle: in addition to these features, we will also see dark, concentric rings called Lines of Arrested Growth (LAGs) representing times when long bone growth temporarily ceased.  Traditionally, it was thought that slow growth and seasonal cessations of that growth produce LAGs, such as the seasonal warming and cooling of “reptiles” from Spring and Summer to Fall and Winter.  However, there have been sporadic reports of LAGs in otherwise fast-growing mammals and birds, and it has been suggested that changes in diet might play a role here.

And this is where a lot of controversy has come in: dinosaur long bones often show LAGs in section, yet are often fibrolamellar with many Haversian canals.  What gives?  If there is any consensus currently, it is apparent that all dinosaurs had some fibrolamellar bone, and most researchers recognize that this indicates a qualitatively rapid growth rate elevated at least somewhat above “reptiles.”  But what about those pesky LAGs?

Enter a new study by Kohler and colleagues published in Nature which shows that lines of arrested growth occur in numerous wild ruminants over a large range of climates.  That’s right — these are endothermic mammals, your cows and antelopes and other hoofed herbivores that have large, multichambered stomachs for processing grasses.  By examining the histological cross-sections of 115 femora from ruminants across Africa and Europe, Kohler and colleagues have shown many examples of LAGs in otherwise “good” endotherms.

What is going on here?  Seasons.  Kohler and colleagues matched the LAGs in their ruminant sample to average rainfall across the various biomes from which the ruminants lived.  What they discovered was that LAGs and slowed growth occurred during times when precipitation was low.  As you might expect, low rates of precipitation will effect plant biomass: fewer plants = fewer calories = less energy available for growth during the lean season.

LAGs in dinosaurs have often been pointed to as either definitive evidence of ectothermy or at least have raised flags concerning how well bone histology conserves information about growth and development.  This study by Kohler and colleagues pretty much ends that argument: LAGs are not associated with the underlying metabolic rate of the animal.  Instead, they reflect changes in bone growth due to the seasonal availability of food and water.

The authors actually say it best at the end of their paper:

The consistently seasonal formation of rest lines in homeothermic endotherms debunks the key argument from bone histology in support of dinosaur ectothermy. Our study instead suggests that the extensive vascularization of the fibrolamellar bone in most dinosaurs and other extinct vertebrates is tightly correlated with seasonal maxima of endogenous heat production, an association that should be explored in future studies. — Kohler et al. (2012), doi:10.1038/nature11264, p. 4

Is this “proof” that dinosaurs were endothermic?  Not exactly, but what is exciting about this new study is that it does indicate that what we are seeing in dinosaur long bone thin-sections is a realistic approximation of their growth rates and an indirect measure of their environments.

Let’s face it: birds are dinosaurs -Part 3-

In the last two posts, I outlined many of the reasons why birds and dinosaurs have been “estranged” and are now being reunited as members of the same clade: Dinosauria.  If you haven’t read these first two posts, check them out:

So, at this point if you’re still not convinced that birds are indeed the living dinosaurs among us, here is one more thing to consider.  Let me take you by the hand …

Embryologists who have studied the development of bird embryos for decades have always come away from studies of their hands with the following conclusion: five initial digits form in cartilage (technically called anlagen), but after awhile, only the three middle digits remain.  Technically, we number digits from the thumb out to the little finger.  So, your thumb would be digit I and your little finger would be digit V.  In birds, the three remaining digits that fuse into the hand are II, III, and IV.  Okay, great, so what?

So this: the earliest predatory dinosaurs had five digits, but the main three digits were I, II, and III, not II, III, and IV.  In fact, during predatory dinosaur evolution, digits IV and V decrease in size until all that is left are I, II, and III.  This contradiction between the digit identities of bird hands and predatory dinosaur hands has been held up as the ultimate “proof” that all the amazing similarities between birds and dinosaurs are just that: amazing convergence.

Enter the past two decades of embryonic science, studies of evo-devo (evolutionary development), and a proliferation of studies combining old-school developmental anatomy with new-school gene studies.  It turns out that the digit identities in the hand are not set like permanent blueprints, but develop from the expression of various developmental genes to concentrations of various proteins.  Without going into great detail, we now know that the identity that digits assume (that is, whether they become I or V or something else) depends on how much of a concentration of particular proteins these regions of the hand were exposed to during development.  Simply put, higher concentrations of certain proteins trigger genes that, when transcribed and translated (i.e., expressed), ultimately create proteins that form digit I, II, III, IV, or V.

Intriguingly, this means that the relative position of a digit in the embryo’s hand and what that digit actually becomes are different.  In other words, a digit in position II could become a digit I if the concentration of various proteins and the expression of certain genes are changed.  This has been called the Frame-shift Hypothesis.  In this case, the “frame” is the region of gene expression that gives digits their identities, whereas the how this gradient moves in the developing hand is the “shift.”  What this all means is that just because you develop a digit in your hand where digit II should be doesn’t at all guarantee that it will become digit II.  It might become digit I, for example, depending on the frameshift.

What this all means is that, hypothetically, at some point during predatory dinosaur evolution, the anlagens that were in positions II, III, and IV frame-shfited to I, II, and III.  This frameshift would, of course, “solve” the digital confusion between birds and dinosaurs, but of course this hypothesis has been questioned and there was no fossil evidence of it occurring in dinosaurs … until recently.

A new Jurassic ceratosaur (a primitive type of predatory dinosaur) from China called Limusaurus preserved a complete hand that looks like an embryonic bird hand!  See for yourself: Figure 2 in their paper.  Now, compare that figure of the ceratosaur hand back to the ostrich hand.  I find this absolutely fascinating and was floored to see a dinosaur hand that looked like something undergoing the hypothesized frameshift.  Here, captured in stone for millions of years, is what you would predict to see in a transitional form going from the primitive predatory dinosaur digit arrangement to the birdy one.  Note in the Limusaurus hand figure that where the first digit is is a splint, like in a bird embryo, and next to that, the digit in the typical place of digit II, is something that looks an awful lot like digit I.

So, to conclude my thread, let me say that it is not at all parsimonious at this point in time to separate birds from dinosaurs.  That is equivalent to separating you from mammals.  It is no longer enough to argue that all the similarities between dinosaurs and birds are due strictly to an amazing amount of convergent evolution.  We have unique skeletal features only birds and dinosaurs share, we have dinosaurs that could not possibly fly possessing feathers, and we even have fossil support to explain why bird and dinosaur hands match up after all.

And finally back to the recent paper that inspired this thread in the first place: Birds have paedomorphic dinosaur skulls.  Paedomorphosis is the retention of juvenilized features into adulthood.  In other words, the proportions of the larva, infant, or juvenile remain relatively unaltered as adults.  This occurs a lot more often in nature than you may realize.  Essentially, the scientists Bhullar and colleagues used a shape analysis technique I have used myself: geometric morphometrics.  This technique analyzes changes in bony landmarks across numerous specimens and provides a mathematical test to see whether the changes predicted are actually significant.  What Bhullar and colleagues discovered was that bird skulls grow as if they were juvenilized dinosaur skulls!  Yet another nail in the coffin (scientifically) for the vague claim that birds cannot be dinosaurs.

Let’s face it: birds are dinosaurs.  I emphasize that I say this in the scientific sense of “certainty.”  Although we can’t be 100% certain in science, these data show overwhelmingly that birds are part of the dinosaur family tree.  When you realize that there are over 10,000 species of living birds but only 4600 or so species of living mammals, you realize it is still the Age of Dinosaurs after all.

Let’s face it: birds are dinosaurs – Part 2 –

To continue from the last post, where were the feathered dinosaurs?  And how did paleontologists begin to reconcile that birds and dinosaurs should start to come together again in their family tree?

Throughout the 1970s and 1980s, the hypothesis of a dinosaur-bird relationship was revived in part because of re-study of the Archaeopteryx specimens, the discovery of the “raptor” known as Deinonychus, and a new approach to understanding evolutionary relationships called cladistics.

Archaeopteryx and Deinonychus are known and discussed in great detail in many sources.  Suffice it to say John Ostrom, among others, began to notice striking skeletal similarities between Archaeopteryx,Deinonychus, and dinosaurs generally.  It was eventually recognized that there are a number of special, shared traits that only seem to occur together in birds and dinosaurs, and especially among predatory dinosaurs and birds.  I could provide a substantial list, but here are a few, selected key features:

  • A fully erect stance where the shaft of the femur (thigh bone) is perpendicular to the femoral head. (Incidentally, the femoral head points inwards towards the pelvis, and this allows the femur to be held vertically.)
  • The ankle is a modified mesotarsal ankle joint.  What this means is that the proximal and distal ankle bones form a cylinder-like roller joint between themselves.  You can see the upper part of this roller joint at the end of a chicken or turkey drumstick, and you also see it in dinosaurs.
  • Predatory dinosaurs and birds have specialized, hollow bones.
  • Predatory dinosaurs and birds have a three-fingered hand, and Archaeopteryx has a clawed, three-fingered hand with deep ligament pits, just like other predatory dinosaurs.
  • A large majority of predatory dinosaurs are classified as tetanurans, and it has been discovered that the tetanuran predators and birds have a furcula.  Despite earlier suggestions to the contrary, many dinosaurs have clavicles and furcula.
  • Coelurosaurs are predatory dinosaurs with specialized wrist bones that allow the hand to swivel sideways.  In other words, the hand doesn’t flex and extend, it rotates sideways towards the ulna.  Guess what other group of vertebrates has this specialized wrist? Birds!
  • Within coelurosaurs are the maniraptorans, the predatory dinosaurs that include Deinonychus and the now universally-knownVelociraptor.  These dinosaurs have highly flexible necks, elongate forelimbs, and the ulna is bowed outwards — the only other vertebrates with these features? Birds.

These observations, while powerful on their own, really started to hit home when placed within a scientifically-testable framework called cladistics.  In a nutshell, cladistics relies on special, shared traits rather than overall similarities to determine common ancestry.  In extremely simplified form, cladistics attempts to do what your family tree does: group everyone together who is related by common ancestry.  Yes, we all have an uncle or group of relatives we wish were not part of our family, but our shared genetic traits still show our close relationships.

Cladistic analyses of dinosaurs among the vertebrates revealed what Huxley had hypothesized all those years ago: birds were not just relatives of dinosaurs, they were a branch of the predatory dinosaur family tree!  Birds were dinosaurs just like humans are mammals.

But where were the feathered dinosaurs?  Until the 1990s, all paleontologists could do is point to the special, shared traits of Archaeopteryx, predatory dinosaurs, and birds and infer that maybe some dinosaurs had feathers.  This ambiguity was seized on by opponents of the birds-as-dinosaurs hypothesis to again suggest all the features (and more) that we have listed here were simply due to an amazing amount of convergent evolution.

Enter the Cretaceous Chinese predatory dinosaur discoveries of the 1990s in the Liaoning Province.  Unprecedented soft-tissue preservation in these fossils showed what was predicted by cladistics, Archaeopteryx, the suite of features shared between dinosaurs and birds only, and even back to Huxley’s observations: unmistakable dinosaurs with unmistakable feathers*.  And not flight feathers, either.  Barb-like and downy-like feathers that ran along the lengths of dinosaurs that could not have flown.  These animals would have used the feathers for insulation and perhaps display, but many could not have flown.  To tick off a few on the list of feathered dinosaurs discovered since the 1990s:

And in the past few years, non-predatory dinosaurs and large predatory dinosaurs with feathers have appeared.  Among them:

This many dinosaurs with feathers, some nowhere near the bird-line let alone among the predatory dinosaurs at all, leads to what we call in science robust evidence.

*Now, the reason for the asterisk — to be absolutely clear and fair, “feather” can be a rather broad term.  Some of these dinosaur feathers are long, hollow barbs, and some don’t branch like modern feathers.  However, Richard Prum and Jan Dyck have demonstrated through detailed studies of feather development in modern birds how feathers begin and diversify.  They have “staged” feathers, meaning that he has hypothesized what the earliest types of feathers should be and so on.  Interestingly enough, the variety of filamentous structures found in the many so-called feathered dinosaur fossils fit these predictions very, very well.

But perhaps you’re still not satisfied that birds are indeed dinosaurs?  Okay, stay tuned …