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Posts Tagged ‘evolution’

Let's play find-the-spandrel!

Let’s play find-the-spandrel!

We just passed the 35th anniversary of the publication of Gould and Lewontin’s classic, highly cited, highly controversial essay (diatribe?), “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme.” The 21st of September 1979 was the fateful date. Every PhD student in biology should read it (you can find pdfs here– this post assumes some familiarity with it!) and wrestle with it and either love it or hate it- THERE CAN BE NO MIDDLE GROUND! With some 5405 citations according to Google Scholar, it has generated some discussion, to put it lightly. Evolutionary physiologists and behaviourists who were working at the time it came out have told me stories of how it sent (and continues to send) shockwaves through the community. Shockwaves of “oh crap I should have known better” and “Hell yeah man” and “F@$£ you Steve,” more or less.

I am among those who love “The Spandrels Paper“. I love it despite its many flaws that people have pointed out to seemingly no end- the inaccurate architectural spandrel analogy, the Gouldian discursive (overly parenthetical [I'm a recovering victim of reading too much Gould as an undergrad]) writing style, the perhaps excessive usage of “Look at some classic non-scientific literature I can quote”, the straw men and so on. I won’t belabour those; again your favourite literature search engine can be your guide through that dense bibliography of critiques. I love it because it is so daringly iconoclastic, and because I think it is still an accurate criticism of what a LOT of scientists who do research overlapping with evolutionary biology (that is, much of biology itself) do.

The aspects of The Spandrels Paper that I still think about the most are:

(1) scientists seldom test hypotheses of adaptation; they are quick to label something that is useful to an animal as an adaptation and then move on after rhapsodizing about how cool of an adaptation it is; and

(2) thus alternatives to adaptation, which might be very exciting topics to study in their own right, get less attention or none.

True for #2, evo-devo has flourished by raising the flag of constraint (genetic/developmental/other factors that prevent evolution from going in a certain direction, or even accelerate it in less random directions). That’s good, and there are other examples (genetic drift, we’ve heard about that sometimes), but option #1 still often tends to be the course researchers take. To some degree, labelling something as an adaptation is used as hype, to make it more exciting, I think, in plenty of instances.

Truth be told, much as Gould and Lewontin admitted in their 1979 paper and later ones, natural selection surely forges lineages that have loads of adaptations (even in the strictest sense of the word), and a lot of useful traits of organisms are thus indeed adaptations by any stripe. But the tendency seems to be to assume that this presumptive commonality of adaptations means that we are justified to quickly label traits as adaptations.

Or maybe some researchers just don’t care about rigorous tests of adaptation as they’re keen to do other things. Standards vary. What I wanted to raise in this post is how I tend to think about adaptation:

I think adaptations are totally cool products of evolution that we should be joyous to imagine, document, test and discover. But that means they should be Special. Precious. A cause for celebration, to carefully document by scientific criteria that something is an adaptation in the strictest sense, and not a plesiomorphy/exaptation (i.e. an adaptation at a different level in the evolutionary hierarchy; or an old one put to new uses), spandrel/byproduct, or other alternatives to adaptation-for-current-biological-role.

But that special-ness means testing a hypothesis of adaptation is hard. As many authors waving the flag of The Modern Comparative Method (TMCM) have contended, sciencing truth-to-adaptationist-power by the rules of TMCM takes a lot of work! George Lauder’s 1996 commentary in the great Adaptation book (pdf of the chapter here) outlined a lengthy procedure of  “The Argument from Design“; i.e., testing adaptation hypotheses. At its strictest implementation it could take a career (biomechanics experiments, field studies, fitness measurements, heritability studies, etc.) to test for one adaptation.

Who has time for all that?

The latter question seems maladaptive, placing cart and horse bass-ackwards. If one agrees that adaptations are Special, then one should be patient in testing them. Within the constraints of the practical, to some degree, and different fields would be forced to have different comfort levels of hypothesis testing (e.g. with fossils you can’t ever measure fitness or other components of adaptation directly; that does not mean that we cannot indirectly test for adaptations– with the vast time spans available, one would expect palaeo could do a very good job of it, actually!).

I find that, in my spheres of research, biomechanists in particular tend to be fast to call things they study adaptations, and plenty of palaeontologists do too. I feel like over-usage of the label “adaptation” cheapens the concept, making the discovery of one of the most revered and crucial concepts in all of evolutionary biology seem cheapened and trite. Things that are so easy to discover don’t seem as precious. When everything is awesome, nothing is…

I’ve always hesitated, thanks in part to The Spandrels Paper’s indoctrination, from calling features of animals adaptations, especially in my main research. I nominally do study major ?adaptations? such as terrestrial locomotion at giant body sizes, or the evolution of dinosaurian bipedalism. I searched through my ~80 serious scientific papers lately and found about 50 mentions of “adapt” in an adaptationist, evolutionary context. That’s not much considering how vital the concept is (or I think it is) to my research, but it’s still some mentions that slipped through, most of them cautiously considered– but plenty more times I very deliberately avoided using the term. So I’m no model of best practice, and perhaps I’m too wedded to semantics and pedantry on this issue, but I still find it interesting to think about, and I’ve gradually been headed in the direction of aspect #2 (above in bold) in my research, looking more and more for alternative hypotheses to adaptation that can be tested.

I like talking about The Spandrels Paper and I like some of the criticism of it- that’s healthy. It’s a fun paper to argue about and maybe we should move on, but I still come back to it and wonder how much of the resistance to its core points is truly scientific. I’m entering into teaching time, and I always teach my undergrads a few nuggets of The Spandrels Paper to get them thinking about what lies beyond adaptation in organismal design.

 What do other scientists think? What does adaptation mean (in terms of standards required to test it) to you? I’m curious how much personal/disciplinary standards vary. How much should they?

For the non-scientists, try this on for size: when our beloved Sir David Attenborough (or any science communicator) speaks in a nature documentary about how the otter is “perfectly adapted” to swim after prey underwater, do you buy into that or question it? Should you? (I get documentaries pushing me *all the time* to make statements like this, with a nudge and a wink when I resist) Aren’t scientists funny creatures anyway?

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[This is the original, unedited text of my shorter, tighter (and I think actually better) News & Views piece for Nature, on the paper described below)

Ambitious experimental and morphological studies of a modern fish show how a flexible phenotype may have helped early “fishapods” to make the long transition from finned aquatic animals into tetrapods able to walk on land.

Stomach-Churning Rating: 1/10. Cute fish. Good science. Happy stomachs!

Photo by Antoine Morin, showing Polypterus on land.

Photo by Antoine Morin, showing Polypterus on land.

Napoleon Bonaparte’s military excursions into Egypt in 1798-1799 led a young French naturalist, Ètienne Geoffroy Saint-Hilaire, to cross paths with a strange fish that had paired lungs and could “walk” across land on its stubby, lobelike fins. In 1802, he dubbed this fish “Polyptère bichir”1, today known as the Nile bichir, Polypterus bichir La Cepède 1803. The bichir’s mélange of primitive and advanced traits helped to catapult Geoffroy into scholarly conflict with the reigning naturalist Georges Cuvier back in France and to establish Ètienne as a leading anatomist, embryologist and early evolutionary researcher of repute even today2. Now, on their own excursion under the very “evo-devo” flag that the discoverer of Polypterus helped raise, Canadian scientists Standen et al.3 suggest how the remarkable plasticity of the skeleton of Polypterus (the smaller west African relative of P. bichir, P. senegalus or “Cuvier’s bichir”) reveals a key part of the mechanism that might have facilitated the gradual transition from water to land and thus from “fishapods” to tetrapods (four-limbed vertebrates).

In a bold experiment, the authors raised 149 young bichirs on land and in water for eight months, then studied how they moved on land vs. in water, and also how the ultimate shape of the skeletal elements of the paired front fin bases differed between the land- and water-raised bichirs. Standen et al.3 discovered that both the form and function of the fins’ foundations transformed to better satisfy the constraints of moving on land. Land-acclimated bichirs took faster steps on land, their fins slipped across the substrate less, they held their fins closer to their body, their noses stayed more aloft and their tails undulated less, with less variable motions overall—behaviours that the authors had predicted should appear to enhance walking abilities on land. In turn, the bones of the neck and shoulder region altered their shape to produce a more mobile fin base with greater independence of fin from neck motion, along with improved bracing of the ventral “collarbone” region. These environmentally-induced traits should have fostered the locomotor changes observed in “terrestrialized” fish and aided the animals in resisting gravity, and they represent a common biological phenomenon termed developmental plasticity4,5. Interestingly, the land-reared fish could still swim about as well as the wholly aquatic cohort, so there was not a clear trade-off between being a good swimmer and a good walker, which is surprising.

Considered alone, the developmental plasticity of bichir form and function shows how impressive these amphibious fish are. But Standen et al.’s study3  ventured further, to apply the lessons learned from bichir ontogeny to a phylogenetic context and macroevolutionary question. The phenotypic plasticity during bichir development, they infer, could have been harnessed during the evolutionary transformation of fins for swimming into limbs for walking, in the “fishapod” ancestors of tetrapods. Indeed, bichirs are close to the base of the family tree of fishes6, and other living relatives of tetrapods have reduced or lost their fins (lungfishes) or adapted to strange deep-sea swimming lifestyles, never walking on land (coelacanths). Thus perhaps bichirs and the “fishapod” lineage share what Geoffroy would have called “unity of type”, today termed homology, of their developmental plasticity in response to a land environment. Surveying the fossil record of early “fishapods” and tetrapods, Standen et al.3 found that the macroevolutionary changes of neck and shoulder anatomy in these gradually more land-adapted animals parallel those they observed in terrestrialized Polypterus, providing ancillary support for their hypothesis.

A further test of the application of Polypterus’s plasticity to fossil tetrapods is naturally difficult. However, the “fishapod” lineage has some exceptional examples of fossil preservation. With sufficient sample sizes (e.g. fossil beds that reveal growth series, such as the Late Devonian Miguasha site in Canada7) and palaeoenvironmental gradients in fish or tetrapods, one could imagine performing a rigorous indirect test. Even small samples could be helpful– for example, the early tetrapod Ichthyostega exhibits some developmental changes in its forelimb suggesting that it became more terrestrial as it grew, whereas the related Acanthostega does not evidence such changes8– this hints at some developmental plasticity in the former animal.

During the Devonian period (~360-420 million years ago), were the “fishapod” ancestors of tetrapods floundering about on land now and then, gradually shifting from anatomy and behaviours that were more developmentally plastic (as in bichirs) to ones that were more canalized into the terrestrialized forms and functions that more land-adapted tetrapods retained? An attractive possibility is that the developmental plasticity could have led to fixation (reduction of plasticity), an evolutionary phenomenon called genetic assimilation, which another intellectual descendant of Geoffroy, Conrad Hal Waddington, promoted from the 1950s onwards9, a concept that now enjoys numerous cases of empirical support10 that this one may eventually join.

The nature of the genetic and developmental mechanism that bichirs use to achieve the observed developmental plasticity is still unclear. If it has a high enough degree of heritability, then it could be selected for in cross-generational experiments with bichirs. With sufficient time and luck raising these unusual fish, the hypothesis that their plastic response to a terrestrial environment can become genetically assimilated could be directly tested. This study could thus become an epic exemplar of how genetic assimilation can contribute not only to microevolutionary change but also to major macroevolutionary events, as was presciently suggested in a seminal review of developmental plasticity4.

This genetic assimilation is the Polypterus study’s reasonable speculation, and one that Geoffroy likely would have applauded, all the more for involving his beloved bichirs. Much as Napoleon’s landfall in Egypt was not a lasting success, bichirs never left wholly terrestrial descendants despite their malleable locomotor system. But the same type of plastic developmental mechanism that bichirs use today to make tentative, floppy incursions of the terrestrial realm might have been harnessed by our own “fishapod” forebears, leaving a far more revolutionary dynasty upon the Earth.

 

References

  1.  Geoffroy, E. (1802). Histoire naturelle et description anatomique d’un nouveau genre de poisson du Nil, nommé polyptère. Annales du Muséum d’Histoire Naturelle 1:57-68.
  2. Le Guyader, H., & Grene, M. (2004) Geoffroy Saint-Hilaire: A Visionary Naturalist. Univ. Chicago Press.
  3. Standen, E. M., Du, T. Y., & Larsson, H. C. E. (2014). Developmental plasticity and the origin of tetrapods. Nature, published online.
  4. West-Eberhard, M. J. (1989). Phenotypic plasticity and the origins of diversity. Annual Review of Ecology and Systematics 20:249-278.
  5. Pigliucci, M., Murren, C. J., & Schlichting, C. D. (2006). Phenotypic plasticity and evolution by genetic assimilation. Journal of Experimental Biology 209(12):2362-2367.
  6. Near, T. J., Dornburg, A., Tokita, M., Suzuki, D., Brandley, M. C., & Friedman, M. (2014). Boom and bust: ancient and recent diversification in bichirs (Polypteridae: Actinopterygii), a relictual lineage of ray‐finned fishes. Evolution 68:1014-1026.
  7. Cloutier, R. (2013). Great Canadian Lagerstätten 4. The Devonian Miguasha Biota (Québec): UNESCO World Heritage Site and a Time Capsule in the Early History of Vertebrates.Geoscience Canada40:149-163.
  8. Callier, V., Clack, J. A., & Ahlberg, P. E. (2009). Contrasting developmental trajectories in the earliest known tetrapod forelimbs.Science324:364-367.
  9. Waddington, C. H. (1953). Genetic assimilation of an acquired character. Evolution 7:118-126.
  10. Crispo, E. (2007). The Baldwin effect and genetic assimilation: revisiting two mechanisms of evolutionary change mediated by phenotypic plasticity. Evolution 61:2469-2479.

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Construction of the Phyletisches Museum in Jena, Germany began on Goethe’s birthday on August 28, 1907. The Art Nouveau-styled museum was devised by the great evolutionary biologist, embryologist and artist/howthefuckdoyousummarizehowcoolhewas Ernst Haeckel, who by that time had earned fame in many areas of research (and art), including coining the terms ontogeny (the pattern of development of an organism during its lifetime) and phylogeny (the pattern of evolution of lineages of organisms through time) which feature prominently in the building’s design and exhibits (notice them intertwined in the tree motif below, on the front of the museum). Ontogeny and phylogeny, and the flamboyant artistic sensibility that Haeckel’s work exuded, persist as themes in the museum exhibits themselves. Haeckel also came up with other popular words such as Darwinism and ecology, stem cell, and so on… yeah the dude kept busy.

Cavorting frogs from Haeckel's masterpiece Kunstformen der Natur (1904).

Cavorting frogs from Haeckel’s masterpiece Kunstformen der Natur (1904).

I first visited the Phyletisches Museum about 10 years ago, then again this August. Here are the sights from my latest visit: a whirlwind ~20 minute tour of the museum before we had to drive off to far-flung Wetzlar. All images are click-tastic for embiggenness.

Stomach-Churning Rating: 3/10 for some preserved specimens. And art nouveau.

Willkommen!

Willkommen!

Frog ontogeny, illustrated with gorgeous handmade ?resin? models.

Frog ontogeny, illustrated with gorgeous handmade ?resin? models.

Fish phylogeny, illustrated with lovely artistry.

Phylogeny of Deuterostomia (various wormy things, echinoderms, fish and us), illustrated with lovely artistry.

Phylogeny of fish and tetrapods.

Phylogeny of fish and tetrapods.

Slice of fossil fish diversity.

Slice of fossil fish diversity.

Plenty of chondryichthyan jaws and bodies.

Plenty of chondrichthyan jaws/chondrocrania, teeth and bodies.

Awesome model of a Gulper eel (Saccopharyngiformes).

Awesome model of a Gulper Eel — or, evocatively, “Sackmaul” auf Deutsch (Saccopharyngiformes).

Lobe-finned fishes (Sarcopterygii)- great assortment.

Lobe-finned fishes (Sarcopterygii)- great assortment including a fossil coelacanth.

Lungfish body/model and skeleton.

Lungfish body and skeleton.

Coelacanth!

Coelacanth!

Coelacanth staredown!

Coelacanth staredown!

Fire salamander! We love em, and the museum had several on display- given that we were studying them with x-rays, seeing the skeleton and body together here in this nice display was a pleasant surprise.

On into tetrapods– a Fire Salamander (Salamandra salamandra)! We love ‘em, and the museum had several on display- given that we were studying them with x-rays, seeing the skeleton and body together here in this nice display was a pleasant surprise.

A tortoise shell and skeleton, with a goofball inspecting it.

A tortoise shell and skeleton, with a goofball inspecting it.

In a subtle nod to recurrent themes in evolution, the streamlined bodies of an ichthyosaur and cetacean shown in the main stairwell of the museum, illustrating convergent evolution to swimming locomotor adaptations.

In a subtle nod to recurrent themes in evolution, the streamlined bodies of an ichthyosaur and cetacean shown in the main stairwell of the museum, illustrating convergent evolution to swimming adaptations.

Phylogeny of reptiles, including archosaurs (crocs+birds).

Phylogeny of reptiles, including archosaurs (crocs+birds).

Gnarly model of an Archaeopteryx looks over a cast of the Berlin specimen, and a fellow archosaur (crocodile).

Gnarly model of an Archaeopteryx looks over a cast of the Berlin specimen, and a fellow archosaur (crocodile). The only extinct dinosaur on exhibit!

Kiwi considers the differences in modern bird palates: palaeognathous like it and fellow ratites/tinamous (left), and neognathous like most living birds.

Kiwi considers the differences in modern bird palates: palaeognathous like it and fellow ratites/tinamous (left), and neognathous like most living birds.

Echidna skeleton. I can't get enough of these!

Echidna skeleton. I can’t get enough of these!

Skulls of dugong (above) and manatee (below).

Skulls of dugong (above) and manatee (below), Sirenia (seacows) closely related to elephants.

Fetal manatee. Awww.

Fetal manatee. Awww.

Adult Caribbean manatee, showing thoracic dissection.

Adult Caribbean manatee, showing thoracic dissection.

Hyraxes, which Prof. Martin Fischer, longtime curator of the Phyletisches Museum, has studied for many years.  Rodent-like elephant relatives.

Hyraxes, which Prof. Martin Fischer, longtime curator of the Phyletisches Museum, has studied for many years. Rodent-like elephant cousins.

Old exhibit at the Phyletisches Museum, now gone: Forelimbs of an elephant posed in the same postures actually measured in African elephants, for the instant of foot touchdown (left pic) and liftoff (right pic). Involving data that we published in 2008!

Old exhibit at the Phyletisches Museum, now gone: Forelimbs of an elephant posed in the same postures actually measured in African elephants, for the instant of foot touchdown (left pic) and liftoff (right pic). Involving data that we published in 2008!

Gorilla see, gorilla do. Notice "bent hip, bent knee" vs. "upright modern human" hindlimb postures in the two non-skeletal hominids.

Eek, primates! Gorilla see, gorilla do. Notice the primitive “bent hip, bent knee” vs. the advanced “upright modern human” hindlimb postures in the two non-skeletal hominids.

Phylogeny of select mammals, including the hippo-whale clade.

Phylogeny of artiodactyl (even-toed) mammals, including the hippo-whale clade.

Hand (manus) of the early stem-whale Ambulocetus.

Hand (manus) of the early stem-whale Ambulocetus.

Carved shoulderblade (scapula) of a bowhead whale (Balaena mysticetus), which apparently Goethe owned. Quite a relic!

Carved shoulderblade (scapula) of a bowhead whale (Balaena mysticetus), which apparently Goethe owned (click to emwhalen and read the fine print). Quite a relic!

One of Haeckel's residences. There is also a well-preserved house of his that one can visit, but I didn't make it there.

One of Haeckel’s residences, across the street from the museum. There is also a well-preserved house of his that one can visit, but I didn’t make it there. I heard it’s pretty cool.

Jena is tucked away in a valley in former East Germany, with no local airport for easy access- but get to Leipzig and take a 1.25 hour train ride and you’re there. Worth a trip! This is where not just ontogeny and phylogeny were “born”, but also morphology as a modern, rigorous discipline. Huge respect is due to Jena, and to Haeckel, whose quotable quotes and influential research still resonate today, in science as well as in art.

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This is the mammoth image I remember, from a 1971 book, with no artist credited. It's actually not as good as I remember, by modern standards at least.

This is the mammoth image I remember, from a 1971 book, with no artist credited. It’s actually not as good as I remember, by modern standards at least.

Mammoths and I go way back, not quite to the Ice Age but at least to the late 1970s with my family’s visits to the University of Wisconsin Geology Museum, and Milwaukee Public Museum, to name two prominent places that inspired me. And one of my favourite science books had a colourful mammoth painting on the cover (above), an image that has stayed with me as awesomely evocative.

Stomach-Churning Rating: 3/10. But there’s a butt below, but that’s too late for you now. And there’s poo and other scatological (attempts at) humour. Otherwise, bones and a baby mammothsicle.

Fast forward to the 2000’s and I’m studying mammoths, along with their other kin amongst the Proboscidea (elephants and relatives). I even bumped into a frozen mammoth in Sapporo, Japan, nine years ago–

Yep. That's what it looks like. Nope, not the front end. That orifice is not the mouth. This is the XXXXX mammoth.

Yep. That’s what it looks like. Nope, not the front end. That dark orifice is not the mouth. This is a mammoth that was found on Bolshoi Lyakhovsky island, in the east Siberian arctic (New Siberian Islands archipelago), in 2003. Just think of finding this and being all excited then realizing, “Jackpot! Wait… Oh man, I just found the ass. I’ve discovered a mammoth bunghole, dammit.” Still, it’s pretty damn amazing, as frozen Ice Age buttocks go. I’d love to find one. I would not be bummed.

found on Bolshoi Lyakhovskiy island in 2003

What I know now that I didn’t realize as a kid, is that a mammoth is an elephant in all but name. Mammoths are more closely related to Asian elephants than either is to African elephants, and all of these elephants are members of the group Elephantidae. If we saw a smallish Columbian mammoth, we’d probably mostly look upon it as similar to a slightly hairy Asian elephant (but a scientist would be able to spot the distinctive traits that each has). Only woolly mammoths adopted the uber-hirsute state that we tend to think of as a “mammoth” trait. Think about it: a big animal would benefit most from a thick hairy insulation in an extremely cold habitat, and Columbian mammoths ranged further south than Woolly ones. No mammoths were radically different from living elephants, unless you count the dwarf ones. But as a kid, like most people do, I saw them as something else: an exotic monster of the past, eerily unlike anything today, and bigger too. And mammoths have the added mystique of the extinct.

Now I see mammoths as neither exotic nor that far in the past. Giant ground sloths, now those are still alien and exotic to me. I don’t get them. I know elephants pretty well, and I can understand mammoths in their light and in light of mammoth fossils. Various mammoth species persisted as late as maybe 10,000 (for the Woolly and Columbian species; the latter seeming to vanish earlier) to <4000 (for isolated Siberian forms) years ago, into quasi-historic times. And only some mammoths got larger than African elephants (Loxodonta) do, such as Columbian mammoths (~10,000 kg or more maximal body mass; Loxodonta is closer to 7-10 tonnes at best).

Lately, coincidence has brought me new knowledge of – and even greater interest in – mammoths.

First, a fortunate last-minute visit to Waco, Texas’s “Mammoth Site” (see my Flickr photo tour here) two weeks ago during a short visit to give a talk in that fine central Texan city.

Second, the subject of today’s post: the Natural History Museum’s new special exhibit “Mammoths: Ice Age Giants“, which is open until 7 September. The exhibit was created by the Field Museum in Chicago, but the NHM has given it a special upgrade under the expert guidance of mammoth guru Prof. Adrian Lister of the NHM, who was very kind to give me a tour of the exhibit.

What follows is primarily a photo-blog post and review of the exhibit, but with some thoughts and facts and anecdotes woven through it. Dark setting, glass cases, caffeination, crowds, and mobile phone camera rather than nice SLR in hand means that the quality isn’t great in my images– but all the more reason to go see the exhibit yourself! All images can be clicked to em-mammoth them.

On entry, one views a mammoth skeleton with a timelapse video backdrop that shows how the landscape (somewhere in USA) has changed since ~10,000 BCE.

On entry, one views a mammoth skeleton with a timelapse video backdrop that shows how the landscape (somewhere in USA) has changed since ~10,000 BCE.

The first part of the exhibit does a nice job of introducing key species of Proboscidea (elephants and their closest extinct relatives), with a phylogeny and timescale to put them into context, starting with the earliest forms:

The first part of the exhibit does a nice job of introducing key species of Proboscidea: from early species like Moeritherium...

from species like the tapir-sized Moeritherium

Skull of Moeritherium, reconstructed. Not that different from an early sirenian (seacow) in some ways, and general shape.

Skull of Moeritherium, reconstructed. Not that different from an early sirenian (seacow) in some ways, and general shape, whereas still quite a long way from a modern elephant in form– but the hints of tusks and trunk are already there.

...To the early elephantiform Phiomia, here shown as a small animal but I'm told it actually got quite large. And continuing with giant terrestrial taxa...

…To the early elephantiform Phiomia, here shown as a smallish animal but I’m told it actually got quite large. And continuing with giant terrestrial taxa…

I was awed by this reconstruction of the giant early elephantiform relative Deinotherium, with the short, swollen trunk and downturned tusks-- so bizarre!

I was awed by this reconstruction of the huge early elephantiform-relative Deinotherium, with the short, swollen trunk and downturned tusks– so bizarre!

Looking down onto the roof of the mouth of a NHM specimen of Deinotherium.

Looking down onto the roof of the mouth of an NHM specimen of Deinotherium. Big, sharper-edged, almost rhino-like teeth; far from the single mega-molars of modern elephants.

The lower jaw (top) and fairly straight tusk (bottom) of the widespread, early elephantiform Gomphotherium.

The lower jaw (top) and fairly straight tusk (bottom) of the widespread, early elephantiform Gomphotherium.

The big "shovel-tusker" elephantiform Amebelodon. This was one of the earliest stem elephants I learned of as a kid; the odd tusks still give me a sense of wonder.

The big “shovel-tusked” elephantiform Amebelodon. This was one of the earliest stem elephants I learned of as a kid; the odd tusks still stir wonder in me.

Amebelodon lower jaw, sans shovel tusks.

Amebelodon lower jaw, sans shovel tusks. Extended chin looks like some sort of childrens’ fun-slide. To me, anyway.

Next, there are some fun interactive displays of elephant biomechanics!

How would a mammoth hold up its head? This lever demonstration shows how a nuchal ligament helps.

How would a mammoth hold up its head? This lever demonstration shows how a nuchal ligament helps. Tension on the nuchal ligament is a force that acts with a large lever (represented by the big neural spines on the vertebrae around the shoulders, forming the mammoths’ “hump” there), creating a large moment (i.e. torque; rotational force) that holds the head aloft.

I love this robotic elephant trunk demonstration. It captures some of the weirdness of having a muscular hydrostat attached to your lip.

I love this robotic elephant trunk demonstration. It captures some of the weirdness of having a muscular hydrostat attached to your lip and nostrils. Not so easy for a human to control!

But forget the myths about elephants having 40,000 to 150,000 muscles in their trunk. They have three muscle layers: a circumferential one, an oblique one and a longitudinal one. Like any muscles, especially ones this large, the layers each consist of many muscle fibres. That’s where the 40-150k myth comes from, but muscle fibres (cells) are at a more microscopic level than whole muscles (organs). Elephants do have excellent control of their trunks, but it’s not magical. It’s just different.

Then we come to the centrepiece of the exhibit, the ~42,000 year old Woolly mammoth (Mammuthus primigenius) baby “Lyuba“, which the NHM added to the original exhibit in this new version, as a star attraction — and a big win. Adrian Lister related to me how he’d never seen Lyuba in person before (access to it was tightly guarded for years). So when the NHM received the crate and held a press event to open it and reveal Lyuba, a journalist asked Adrian to act excited, to which he responded something like, “I don’t need to act! I’m very excited!” I would be, too! Full story on Lyuba’s arrival, by NHM site here. A key paper on Lyuba by Fisher et al. is here.

Studies of tooth growth in Lyuba reveal her gestation period (like living elephants, around 22 months), season of birth (early spring), and age at death (1 month), among other information.

Studies of tooth growth in Lyuba reveal her gestation period (like living elephants, ~22 months), season of birth (early spring), and age at death (~1 month), among other information.

Here we can see the right ear, which was gnawed off along with the tail by dogs of the reindeer herders that found and retrieved Lyuba. Regardless, there's loads of anatomy preserved! A hump of juvenile "brown fat" atop the head, very strange flanges on the trunk (also visible in 1 other frozen mammoth specimen, but here preserved very clearly!), and more visible postcranially...

Here we can see the right ear, which was gnawed off along with the tail by dogs of the reindeer herders that found and retrieved Lyuba in 2006. Regardless, there’s loads of anatomy preserved!

A hump of juvenile “brown fat” sits atop the head and neck of Lyuba. This probably was  metabolized during growth to warm the baby; brown fat is packed with mitochondria and thereby conducts what is called “non-shivering thermogenesis”. Furthermore, Lyuba has very strange flanges on the trunk (also visible in 1 other frozen mammoth specimen, but here preserved very clearly! What were they used for?). More details are visible postcranially…

The body was naturally “freeze-dried”, with the addition of later rounds of soaking in formalin and ethanol, leaving the body dessicated and stiff, permanently stuck in a lifelike pose as seen below:

Whole view from an exhibit panel (you cannot photograph the specimen but these are fair game!). Here we see hair on the right forearm and remnant of the ear, and the labia and nipples showing it is a female mammoth are also preserved. The head-hump is lost during growth, and the shoulder changes to change the Asian elephant-like convex curvature of the back into the characteristic humped-shoulder form of a mammoth. But ontogeny still reveals the evolutionary connection of Elephas and Mammuthus.

Whole view from an exhibit panel (you cannot photograph the specimen but these are fair game!). Here we see hair on the right forearm and remnant of the ear, and the labia and nipples showing it is a female mammoth are also preserved. The head-hump is lost during growth, and the shoulder changes to change the Asian elephant-like convex curvature of the back into the characteristic humped-shoulder form of a mammoth. But ontogeny still reveals the evolutionary connection of Elephas and Mammuthus.

Lyuba and scientists studying her, which also shows how rigid the carcass is.

Lyuba and scientists studying her, which also shows how rigid the carcass is; one can almost stand it up. Inside the digestive tract, researchers found chewed up plant material that was probably dung eaten by the baby to gain vital bacterial digestive flora, and Lyuba had plenty of body fat and ingested milk, indicating that she did not starve to death. Rather, vivianite in the respiratory tract indicates drowning as the cause of her demise. Perfusion of the body by these vivianites may have helped to preserve the body.

Answering an question the public may be wondering about: is the hype about cloning a mammoth very soon true? Nope. Well addressed, including what to me is the urgent question: would cloning a mammoth be ethical?

Answering a question the public may be wondering about: is the hype about cloning a mammoth very soon true? Nope. Well addressed, including what to me is the urgent question: would cloning a mammoth be ethical?

The fourth part of the exhibit takes on a largely North American focus to first illustrate what mammoths were like biologically, and second to wow the visitor with some huge beasts in full body, full scale glory, as we shall see!

Mammoth hair! These samples and recent molecular studies show that mammoths were not ginger-coloured as we long thought, but rather the ginger color comes as the dark grey-brown-black colour fades postmortem, as a preservational artefact. I didn't know that; cool.

Mammoth hair! These samples and recent molecular studies show that mammoths were not ginger-coloured as we long thought, but rather the ginger color comes as the dark grey-brown-black colour fades postmortem, as a preservational artefact (story here). I didn’t know that; cool.

Mammoth chow!

Mammoth chow! I liked this addition to the exhibit. This brought mammoth ecology closer to home for me.

Mammoth poop!

Mammoth poop!

After the biology explanations, let there be megafauna!

Mammoth skull! A nice one, too.

Mammoth skull! A nice one, too.

Top predators of Ice Age North America: Arctodus (short-faced bear) and Homotherium (sabre-toothed cat).

Top predators of Ice Age North America: Arctodus (short-faced bear– does the short face mean they were happy, unlike a long face? Sorry but they never are shown as very happy, unless it is the joy of whupass) and Homotherium (the other sabre-toothed cat; not the longer-toothed Smilodon).

Skulls of North American megafauna: left to right, top to bottom: horse, short-faced bear, giant sloth, then camel, sabretooth,  rabbit, direwolf (viva Ned Stark!), and pronghorn antelope.

Skulls of North American (mega)fauna: left to right, top to bottom: horse, short-faced bear, giant ground sloth, then camel, sabretooth cat, rabbit, direwolf (viva Ned Stark!), and pronghorn antelope.

Mastodon skeleton!

Mastodon (Mammut americanum) skeleton!

Mammoths seem to have been wiped out by a combination of climate change and habitat fragmentation, combined with what this item symbolizes: human hunting. This beautiful piece is the main part of an atlatl, or javelin-hurling lever. It would give Ice Age hunters the extra power they'd need to penetrate mammoth hide and cause mortal injuries.

Mammoths (and perhaps mastodons, etc.) seem to have been wiped out by a combination of climate change and habitat fragmentation, combined with what this item symbolizes: human hunting. This beautiful piece is the main part of an atlatl, or javelin-hurling lever. It would have given Ice Age hunters the extra power they’d need to penetrate mammoth hide and cause mortal injuries. It is also a great tie-in to my recent post on the British Museum’s odd-animals-in-art.

Finally, the exhibit surveys the kinds of mammoths that existed- there is a huge reconstruction of a Columbian mammoth near the mastodon (above), then smaller kinds and discussions of dwarfism, which is another strength of NHM mammoth research:

Woolly mammoth lower jaw (right) and its likely descendant, the pygmy mammoth of the Californian coastline, Mammuthus exilis.

Woolly mammoth lower jaw (right) and its likely descendant, the pygmy mammoth of the Californian coastline, Mammuthus exilis.

The world's smallest mammoth (left), molar tooth compared with that of its much larger ancestor Palaeoloxodon. The status of Mammuthus creticus as a dwarf mammoth from Crete was cemented by Victoria Herridge and colleagues, including Adrian Lister at the NHM.

The world’s smallest mammoth (left), molar tooth compared with that of its much larger ancestor Palaeoloxodon. The status of Mammuthus creticus as a dwarf mammoth from Crete was cemented by Victoria Herridge and colleagues, including Adrian Lister at the NHM.

Pygmy mammoth reconstruction. Shorter than me. I want one!

Pygmy mammoth reconstruction. Shorter than me. I want one!

In the end, from all that proboscidean diversity we were left with just 2 or 3 species (depending on your species concepts; it's probably worth calling the African forest elephant its own species, Loxodonta cyclotis). The exhibit closes with a consideration of their conservation and fate. Ironically, this elephant skull could not be mounted with its tusks on display, because that would be commercializing ivory usage-- even though the whole point of the exhibit's denouement is to explain why elephants need protection!

In the end, from all that glorious proboscidean diversity we were left with just 2 or 3 species of elephantids today (depending on your species concepts; it’s probably worth calling the African forest elephant its own species, Loxodonta cyclotis). The exhibit closes with a consideration of their conservation and fate. Ironically, this elephant skull could not be mounted with its tusks on display, because that would be commercializing ivory usage– even though the whole point of the exhibit’s denouement is to explain why elephants need protection!

Reactions to the exhibit: the photos tell the tale. It’s undeniably great, in terms of showing off the coolness of mammoths, other proboscideans and Ice Age beasties, to the general public. I felt like the factual content and learning potential was good. It didn’t feel at all like pandering to the lowest common denominator like some other exhibits I’ve seen (cough, Dino Jaws, cough). I loved the reconstructions, which were top quality in my opinion. I could have done with some more real skeletons, yet more realistically the exhibit hall was already large and full of cool stuff. But give me a break: Lyuba. This trumps everything. Going to see a real friggin’ frozen mammoth baby buries the needle of the awesomeness meter on the far right. That’s pretty much all I need to say. The spectacle was a spectacle.

This exhibit shows a lot of work, a lot of thought, and a personalized NHM touch that reflects the actual research (even very recent work!) that NHM staff like Prof. Lister are doing with collaborators around the globe. What more could we want, a herd of cloned mammoth babies frolicking around and tickling guests with their flanged trunks? Don’t hold your breath.

You’ve got just over 2 months to see the exhibit. Don’t come complaining on September 8 “BBBBBbbbut I didn’t know, I didn’t think it would be that cool! I just thought there’d be a guy in a Snuffleupagus suit signing autographs!” You have a duty as a Freezerino to go bask in the frozen glory of these Ice Age critters. There may be an exam at the end. :)

Is the exhibit kid-friendly? More or less. The text is more targeted at teenager-level or so, but the visual impact is powerful without it. I’d warn a sensitive child about the withered baby mammoth body before showing it to them, so they aren’t caught off guard and scarred by the experience. I saw plenty of kids in the exhibit and they all seemed happy. Parents may want to linger longer and absorb all the interesting information, whereas kids may blitz through or goof around, so plan accordingly if you’re inbound with sprogs.

You know what I was eyeing up in the gift shop...

You know what I was eyeing up in the gift shop…

Aside: The frozen mammoths get me wondering- what else does the Siberian (or extreme northern Canadian/Scandinavian) permafrost conceal? There are a lot of awesome Ice Age megafauna I’d cut my left XXXXX off to study quasi-intact… think about how amazing it would be to find a giant ground sloth (not bloody likely), sabretooth cat, or other species. There’s a lot of north up north. A lot of space and ice. A lot could happen. And climate change will make discoveries like this more likely, while the melting (and humanity) lasts…

Wool we ever find the Lyuba of woolly rhinos? It could happen.

Wool we ever find the Lyuba of woolly rhinos (Coelodonta)? Cast of a mummified woolly rhino from the NHM’s entry hall. More of these finds are likely, I’d say.

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A very short post here to plug BBC Radio 4’s excellent second series of “Just So Science”. These are 15 minute stories involving a reading of parts of Rudyard Kipling’s great British/natural history stories, and then examining how the science of today informs us about the real lives of animals, without resorting to just-so stories a la Kipling (co-opted as a term in evolutionary biology, too!). I was featured last year on rhinos.

I’m featured this year on kangaroos (now available online) and elephants (also available online now). I just listened to the kangaroo episode and it was good fun. I’ve studied the biomechanics of kangaroos a bit, in as-yet unpublished work featured here in a BBC News story (video from that work is below), and we’ve done other work on their bone morphology and how it relates to body size that is sure to come out in not too long.

Don’t blink! Or, for your enjoyment, a looping GIF:

kangaroo hop

My freezers feature heavily in one bit, in which you can hear me vent my frustrations about an unlabelled bag and stacks of specimens– where is the wallaby? And what’s that crinkling noise?

Best beloved, it is the sound of science. Just so. Enjoy!

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Less words, more pictures in this post, and I’ll get the one lame cake joke out of the way early. I’ve nearly finished my research blitz through the postcranial material of the NHM-Tring’s osteological collection and have made some pit-stops for cake skulls now and then when I see one that pleases me. Now I shall present a survey of some of the species I’ve examined. I’ll proceed up from the base of the crown clade of living birds (Neornithes/Aves; the most recent common ancestor of living birds and all its descendants) and first take a tour of Palaeognathae; the ratites and kin; then move another step up into the Neognathae, first featuring the lineage featuring the ground fowl (Galliformes) and then the waterfowl (Anseriformes). If all this taxonomy and phylogeny is a bit much, check out this page for a brush-up on the bushy branches of bird biodiversity.

First, lots of bones of our cast of currasows, chachalacas, cassowaries and other kooky characters. And then, perhaps, a stop to the excessive alliteration. Finally, I will finish with some examples of species oddity (hat tip to Chris Hadfield).

Stomach-Churning Rating: 2/10- some bony pathologies but still just dry bones. Minimal cake jokes, and no filthy swearing this time.


BRING ON THE BONES:

My photographs are shown with kind permission from the Natural History Museum, London.

Exploded skull of an ostrich/ This takes skill.

Exploded skull of an ostrich, Struthio camelus. This kind of careful preparation takes crazy skill, and creates a thing of rare beauty.

Neat skull of a cassowary, Casuarius casuarius.

Imposing skull of a cassowary, Casuarius casuarius, with a rather worn head casque.

Mummified Owen's Little Spotted kiwi, Apteryx owenii.

Mummified Owen’s Little Spotted Kiwi, Apteryx owenii. The feathers were still soft and fluffy, but I would not call this specimen cuddly.

Dorsal view of the back/hips of the Great Spotted kiwi, Apteryx haasti.

Dorsal view of the back/hips of the Great Spotted Kiwi, Apteryx haasti. I like this photo and am not sure why. The symmetry and shading pleases me, I guess.

Front view of the back/hips of the Great Spotted kiwi, Apteryx haasti.

Front view of the back/hips of the Great Spotted Kiwi, Apteryx haasti, watching over my laptop and watching me while I write this blog on my laptop… so meta(ornithine)!

Wing of a kiwi, showing the fragile bones and feather attachments.

Wing of a kiwi, showing the fragile bones and feather attachments. “Apteryx” = “no wings”… well not quite. Click to emkiwi(?) so you can identify the individual bones, from the humerus right down to the fingers! I love this specimen.

The left leg (in front view) of the elephant-bird, Aepyornis maximus, from Madagascar, with a small moa nearby in left side view.

The titanic left leg (in front view) of the Elephant Bird, Aepyornis maximus, from Madagascar, with a small moa nearby in left side view. There’s so much awesomeness about elephant birds I don’t know where to start, but this is one good place to do so.

Mummified Unulated tinamou, Crypturellus undulatus.

The smaller end of the palaeognath scale: a mummified Undulated Tinamou, Crypturellus undulatus. Somehow the head got stuck into the abdominal cavity underneath the sternum, so this tinamou almost had its head up its arse. A tinamou with head in its proper position looks and sounds like this (video).

And now we take a left turn into the Galloanseres, most basal branch of the neognath birds, to see some of the neglected, strange early branches off from the “main line” that led to the modern diversity of ducks, geeses and swans (Anatinae, Anserinae).

Screamers (Anhimidae) are to Anseriformes as megapodes (see below; brush turkeys) are to Galliformes. By that I mean that both screamers and megapodes are very early branches off the main line of their respective lineages’ evolution, and both are quite strange when seen in that context… an unfair one, frankly; over-focused on the most familiar, “modern” or most speciose group. More about this issue further below.

This was my first hands-on experience with screamer anatomy; I was familiar from reading Tetrapod Zoology and other material about them. Check out the sound that gives them their name here! I’m now a big fan- they have so many strange features: oddly chunky but often very light bones, big feet with long toes, and then these switchblade-wrists, which would make Batman jealous:

Crested screamer, Chauna torquata, showing the wicked spur on the carpometacarpus.

Crested Screamer, Chauna torquata, showing the wicked spur (and smaller one) on the carpometacarpus.

Horned screamer, Anhima cornuta; similar carpometacarpal spur as in Chauna.

Horned Screamer, Anhima cornuta; similar carpometacarpal spurs as in Chauna.

Torso of a screamer seen in top view. Nice narrow body.

Torso of a screamer seen in top view. Nice narrow body, and no uncinate processes (spur-like bony struts that cross the ribs and act as levers for the muscles that move the ribcage during breathing)

The long, gracile, clawed toes of a screamer.

The long, gracile, clawed toes of a screamer. Those toes, especially as they belong to an animal called a screamer, are spooky for me. Note also: very little toe-webbing for a “waterfowl.”

Not to be outdone, on the Galliformes side of Galloanserae, we have some funky headgear in the Maleo (a megapode bird/Megapodiidae; a very basal branch of “brush turkeys” and kin) and curassows (part of the Cracidae; odd South American birds whose males make booming sounds, presumably using their head-casques as resonating chambers?):

Skull of a male maleo, Macrocephalon maleo.

Skull of a male Maleo, Macrocephalon maleo. AR Wallace famously pursued it, and here is its funky call.

Australian brush-turkeys, Alectura lathami i, at the Alma Park Zoo near Brisbane, Australia; they run wild there. Here they are doing what they are best known for: making a mound-like nest.

Australian brush-turkeys, Alectura lathami, at the Alma Park Zoo near Brisbane, Australia; they run wild there. Here they are doing what they are best known for: making a mound-like nest. We were doing kangaroo biomechanics experiments and they were everywhere. I was in awe to see such exotic (to me) birds; locals seemed not so enthused (the birds are loud and make a lot of mess).

Skull of Helmeted curassow, Crax/Pauxi pauxi.

Skull of Helmeted Curassow, Crax/Pauxi pauxi,  showing that resonating chamber. Along with this boom-boom-room, the male uses a piece of food that he holds to draw in the female; if she takes it, then it’s sexy time.

Foot of a Russian Black Grouse, Tetrao tetrix (nothing to do with a certain videogame), with and without flesh.

Foot of a Siberian Black Grouse, Tetrao tetrix (nothing to do with a certain videogame), with and without flesh. Regard the broad, feathered feet, well insulated and with plenty of surface area for prancing around in the snow or moorlands. Tetrao engage in a cool display pattern called lekking, in which the males group together and show off to watching females.

A theme in the section above that is not to be missed is that there is some amazing disparity of anatomical forms in these basal lineages of poultry-relatives. Don’t dismiss the Galloanserae as just boring food-birds! Heaps of not-so-well-studied species exist here, surely with a treasure trove of cool neontological and evolutionary questions waiting for the right person to ask! Darwin’s chickens may get their share of neglect, but that pales in comparison to how little we understand about many basal Galloanserae.

What a lot of people think of as a “ground fowl” or galliform way of life is more of a way of life somewhat typical of the Phasanidae- chickens, pheasants and their familiar kin. Megapodes, curassows, guans, grouse and other Galliformes do not necessarily do things in the “typical” ground fowl way, much as the earlier branches of the Anseriformes don’t always look/act like “proper water fowl” (i.e. Anatidae). The phenomenon at play here is one of the great bugaboos in biology: essentialism– the often implicit misconception that variation away from some abstract ideal is negligible, uninteresting or just not conceivable due to mental blinders. When we say something like “the chicken is a fascinating species” we are sliding down the essentialistic slope. There is no “the chicken.” Not really. Oh dear, speaking of slippery slopes, I’d best stop here before I start talking about species concepts. And no one wants that to happen! Anyway, essentialism still pervades a lot of modern scientific thinking, and has its place as a conceptual crutch sometimes. But in biology, essentialism can be very insidious and misleading. It burrows in deep into the scientific mind and can be hard to root out. Unfortunately, it is entrenched in a lot of science education, as it makes things easier to teach if you sweep aside the exceptions to the essentialist “rules” in biology. I catch myself thinking in static, essentialist ways sometimes. The punishment is no cake for a week; so awful. :)

And speaking of “normal” or “typical,” morphology is of course often not that way even within a species, age class or gender. Pathology is a great example; by definition it is abnormal. It is a shattering of the “essence” of animals, brought on by some malady.

Next I’ve highlighted some of the amazing pathologies I’ve seen in the Tring skeletons. There have been so many I’ve been unable to keep track of them– some of these birds had the stuffing beaten out of them, and I’m not talking about Thanksgiving turkeys. Some were captive animals, in which the pathology might be blamed on living an inappropriate environment, but some were wild-caught — given the extreme pathologies, it’s a wonder those even survived to be found, but perhaps less a surprise that they were caught.


BONES GONE BONKERS:

View of left knee of a specimen of the Highland guan, Penelopina nigra, showing some nasty osteoarthritis around the whole joint.

View of left knee of a specimen of the Highland Guan, Penelopina nigra, showing some nasty osteoarthritis around the whole joint. Eew.  A happier Guan sounds like this.

Femora and tibiae of the Blue-throated Piping Guan, Aburria cumanensis. Amazing pathology involving the left femur (broken, rehealed) and tibiotarsus (secondary infection?).

Femora and tibiotarsi of the Blue-throated Piping Guan, Aburria cumanensis. Amazing pathology involving the left femur (broken, rehealed) and tibiotarsus (secondary infection?). Interestingly, the non-fractured limb also showed some pathology, perhaps indicating general infection and/or arthritis in reaction to the severe damage to the other leg, or just increased load-bearing on that leg.

Little Chachalaca, Ortalis motmot, showing a broken and rehealed right femur and the tibiotarsus.

Little Chachalaca, Ortalis motmot, showing a broken and rehealed right femur and the tibiotarsus. As in the guan above, this animal was not walking for many weeks; its femur had snapped in two, but somehow melted back together. The tibiotarsus didn’t look too great, either; lumpy and bendy. In better times, the Chachalaca does the cha-cha like this.

These two specimens blew my mind. On the right is a normal Tetrao tetrix (Black grouse); on the left is one hybridized with another (unknown) species.

These two specimens blew my mind. On the left is a normal Tetrao tetrix (Black Grouse); on the right is one hybridized with another (unknown) species.

In the picture above, what amazed me first was the very unusual flattened pelvis/synsacrum of Tetrao, which characteristically is light and wide. But in the hybrid this morphology was completely gone; the pelvis had a more standard “galliform” (read: Phasianid)-like shape, deeper and narrower and more solid in build. I am guessing that the hybrid was a cross with a pheasant like Phasianus itself, whose anatomy would be more like this. Somewhere in here there is a fantastic evo-devo/morphometrics project waiting to happen.

That’s my quick specimen-based tour of “basal birds”. Beyond these two clades of Palaeognathae and Galloanseres, there lies the forebidding territory of Neoaves: much of living avian diversity, and extremely contentious in its phylogenetic relationships. I’m tackling them next for my research on the evolution of the patella/kneecap. But first, I’ll be at the NHM-Tring today for a whirlwind tour through the respectably speciose “normal” Galloanseres clades of Phasianidae and Anserinae+Anatidae, so off I go! (It’s my wife’s birthday celebration, so cake may have to wait for later this time)

So what do you think? What’s your favourite neglected “primitive” bird group (more apropos: early branching avian lineage that may still be very specialized, rare and poorly understood), or cool factoid about palaeognaths and basal neognaths?

No quaggas were harmed during the writing of this post.

No quaggas were harmed during the writing of this post. Polly wanna quagga?

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Models of a basal dinosaur and bird, showing methods and key differences in body shape.

Our 3D computer models of a basal dinosaur and bird, showing methods and key differences in body shape. The numbers at the bottom are museum specimen numbers.

At about the moment I’m posting this, our Nature paper (our more formal page here, and the actual article here) embargo is ending, drawing a 14+ year gestation to a close. The paper is about how dinosaur 3D body shape changed during their evolution, and how that relates to changes in hindlimb posture from early dinosaurs/archosaurs to birds; “morpho-functional evolution” sums up the topic. We used the 3D whole-body computational modelling that I, Allen and Bates (among others) have developed to estimate evolutionary changes in body dimensions, rather than focusing on single specimens or (as in our last study) tyrannosaur ontogeny. We’ve strongly supported the notion (dating back to Gatesy’s seminal 1990 Paleobiology paper) that the centre of mass of dinosaurs shifted forwards during their evolution, and that this shift gradually led to the more crouched (flexed) hind leg posture that characterizes living birds. Here is a movie from our paper showing how we did the modelling:

And here is a summary of our 17 computer models of archosaur bodies, shown as one walks along the tips of the phylogeny shown in the video (the models are not considered to be ancestral to one another; we used a common computer algorithm called squared-change parsimony to estimate ancestral state changes of body dimensions between the 16 numbered nodes of the tree):

But we’ve done much more than just put numbers on conventional wisdom.

We’ve shown, to our own surprise, that the shift of the centre of mass was largely driven by evolutionary enlargements of the forelimbs (and the head and neck, and hindlimbs, to a less strong degree), not the tail as everyone including ourselves has assumed for almost 25 years. And the timing of this shift occurred inside the theropod dinosaur group that is called Maniraptora (or Maniraptoriformes, a slightly larger group), so the change began in animals that were not flying, but not long before flight evolved (depending on whom you ask, what taxonomy they favour and what evidence one accepts, either the smaller clade Eumaniraptora/Paraves or the bird clade Aves/Avialae).

Now, if you don’t like the cliche “rewriting the textbooks”, do have a look through texts on dinosaur/early avian palaeobiology and you probably will find a discussion of how the tail shortened, the centre of mass moved forwards as a consequence, the caudofemoral musculature diminished, and theropod dinosaurs (including birds) became more crouched as a result. We did that to confirm for ourselves that it’s a pretty well-accepted idea. Our study supports a large proportion of that idea’s reasoning, but modifies the emphasis to be on the forelimbs more than the tail for centre of mass effects, so the story gets more complex. The inference about caudofemoral muscles still seems quite sound, however, as is the general trend of increased limb crouching, but our paper approximates the timing of those changes.

Figure 3 from our paper, showing how the centre of mass moved forwards (up the y-axis) as one moves toward living birds (node 16); the funny dip at the end is an anomaly we discuss in the paper.

Figure 3 from our paper, showing how the centre of mass moved forwards (up the y-axis) as one moves toward living birds (node 16); the funny dip at the end is an anomaly we discuss in the paper.

A final implication of our study is that, because the forelimbs’ size influenced the centre of mass position, and thus influenced the ways the hindlimbs functioned, the forelimbs and hindlimbs are more coupled (via their effects on the centre of mass) than anyone has typically considered. Thus bipedalism and flight in theropods still have some functional coupling– although this is a matter of degree and not black/white, so by no means should we do away with helpful concepts like locomotor modules.

And in addition to doing science that we feel is good, we’ve gone the extra mile and presented all our data (yes, 17 dinosaurs’ worth of 3D whole body graphics!) and the critical software tools needed to replicate our analysis, in the Dryad database (link now working!), which should have now gone live with the paper! It was my first time using that database and it was incredibly easy (about 1 hour of work once we had all the final analysis’s files properly organized)– I strongly recommend others to try it out.

That’s my usual general summary of the paper, but that’s not what this blog article is about. I’ll provide my usual set of links to media coverage of the paper below, too. But the focus here is on the story behind the paper, to put a more personal spin on what it means to me (and my coauthors too). I’ll take a historical approach to explain how the paper evolved.


This paper’s story, with bits from the story of my life:

Embarassing picture of me before I became a scientist. Hardee's fast food restaurant cashier, my first "real job."

Embarassing picture of me before I became a scientist. Hardee’s fast food restaurant cashier, my first “real job”, from ~1999- no, wait, more like 1986. The 1980s-style feathered (and non-receding) hair gives it away!

Rewind to 1995. I started my PhD at Berkeley. I planned to use biomechanical methods and evidence to reconstruct how Tyrannosaurus rex moved, and started by synthesizing evidence on the anatomy and evolution of the hindlimb musculature in the whole archosaur group, with a focus on the lineage leading to Tyrannosaurus and to living birds. As my PhD project evolved, I became more interested and experienced in using 3D computational tools in biomechanics, which was my ultimate aim for T. rex.

In 1999, Don Henderson published his mathematical slicing approach to compute 3D body dimensions in extinct animals, which was a huge leap for the field forward beyond statistical estimates or physical toy models, because it represented dinosaurs-as-dinosaurs (not extrapolated reptiles/mammals/whatever) and gave you much more information than just body mass, with a lot of potential to do sensitivity analysis.

I struggled to upgrade my computer skills over the intervening years. I was developing the idea to reconstruct not only the biomechanics of T. rex, but also the evolutionary changes of biomechanics along the whole archosaur lineage to birds– because with a series of models of different species and a working phylogeny, you could do that. To me this was far more interesting than the morphology or function of any one taxon, BUT required you to be able to assess the latter. So Tyrannosaurus became a “case study” for me in how to reconstruct form and function in extinct animals, because it was interesting in its own right (mainly because of its giant size and bipedalism). (Much later, in 2007, I finally finished a collaboration to develop our own software package to do this 3D modelling, with Victor Ng-Thow-Hing and F. Clay Anderson at Honda and Stanford)

Me and a Mystery Scientist (then an undergrad; now a successful palaeontologist), measuring up a successful Cretaceous hypercarnivore at the UCMP; from my PhD days at Berkeley, ~2000 or so.

Me and a Mystery Scientist (then an undergrad; now a very successful palaeontologist!), measuring up a successful Cretaceous hypercarnivore at the UCMP; from my PhD days at Berkeley, ~2000 or so.

In all this research, I was inspired by not only my thesis committee and others at Berkeley, but also to a HUGE degree by Steve Gatesy, a very influential mentor and role model at Brown University. I owe a lot to him, and in a sense this paper is an homage to his trailblazing research; particularly his 1990 Paleobiology paper.

In 2001, I got the NSF bioinformatics postdoc I badly wanted, to go to the Neuromuscular Biomechanics lab at Stanford and learn the very latest 3D computational methods in biomechanics from Prof. Scott Delp’s team. This was a pivotal moment in my career; I became partly-an-engineer from that experience, and published some papers that I still look back fondly upon. Those papers, and many since (focused on validating and testing the accuracy/reliability of computer models of dinosaurs), set the stage for the present paper, which is one of the ones I’ve dreamed to do since the 1990s. So you may understand my excitement here…

Stanford's Neuromuscular Biomechanics Lab, just before I left in 2003.

Stanford’s Neuromuscular Biomechanics Lab, just before I left in 2003.

But the new paper is a team effort, and was driven by a very talented and fun then-PhD-student, now postdoc, Dr Vivian Allen. Viv’s PhD (2005-2009ish) was essentially intended to do all the things in biomechanics/evolution that I had run out of time/expertise to do in my PhD and postdoc, in regards to the evolution of dinosaur (especially theropod) locomotor biomechanics. And as I’d hoped, Viv put his own unique spin on the project, proving himself far better than me at writing software code and working with 3D graphics and biomechanical models. He’s now everything that I had hoped I’d become by the end of my postdoc, but didn’t really achieve, and more than that, too. So huge credit goes to Viv for this paper; it would never have happened without him.

We also got Karl Bates, another proven biomechanics/modelling expert, to contribute diverse ideas and data. Furthermore, Zhiheng Li (now at UT-Austin doing a PhD with Dr Julia Clarke) brought some awesome fossil birds (Pengornis and Yixianornis) from the IVPP in Beijing in order to microCT scan them in London. Zhiheng thus earned coauthorship on the paper — and I give big thanks to the Royal Society for funding this as an International Joint Project, with Dr Zhonghe Zhou at the IVPP.

That’s the team and the background, and I’ve already given you the punchlines for the paper; these are the primitive and the derived states of the paper. The rest of this post is about what happened behind the scenes. No huge drama or anything, but hard, cautious work and perseverance.

Me shortly after I moved to the RVC; video still frame from a dinosaur exhibit I was featured in. Embarassingly goofy pic, but I like the blurb at the bottom. It's all about the evolutionary polarity, baby!

Me shortly after I moved to the RVC; video still frame from a dinosaur exhibit (c. 2004) I was featured in. Embarassingly goofy pic, but I like the blurb at the bottom. It’s all about the evolutionary polarity, baby!

The paper of course got started during Viv’s PhD thesis; it was one of his chapters. However, back then it was just a focus on how the centre of mass changed, and the results for those simple patterns weren’t very different from those we present in the paper. We did spot, as our Nature supplementary information notes,  a strange trend in early theropods (like Dilophosaurus; to a lesser degree Coelophysis too) related to some unusual traits (e.g. a long torso) and suggested that there was a forward shift of centre of mass in these animals, but that wasn’t strongly upheld as we began to write the Nature paper.

On the urging of the PhD exam committee (and later the paper reviewers, too), Viv looked at the contributions of segment (i.e. head, neck, trunk, limbs, tail) mass and centre of mass to the overall whole body centre of mass. And I’m glad he did, since that uncovered the trend we did not expect to find: that the forelimb masses were far more important for moving the centre of mass forwards than the mass (or centre of mass) of the tail was– in other words, the statistical correlation of forelimb mass and centre of mass was strong, whereas changes of tail size didn’t correlate with the centre of mass nearly as much. We scrutinized those results quite carefully, even finding a very annoying bug in the 3D graphics files that required a major re-analysis during peer review (delaying the paper by ~6 months).

The paper was submitted to Nature first, passing a presubmission inquiry to check if the editor felt it fit the journal well enough. We had 3 anonymous peer reviewers; 1 gave extensive, detailed comments in the 3 rounds of review and was very fair and constructive, 1 gave helpful comments on writing style and other aspects of presentation as well as elements of the science, and 1 wasn’t that impressed by the paper’s novelty but wanted lots more species added, to investigate changes within different lineages of maniraptorans (e.g. therizinosaurs, oviraptorosaurs). That third reviewer only reviewed the paper for the first round (AFAIK), so I guess we won them over or else the editor overruled their concerns. We argued that 17 taxa were probably good enough to get the general evolutionary trends that we were after, and that number was ~16 more species than any prior studies had really done.

Above: CT scan reconstruction of the early extinct bird Yixianornis in slab conformation, and then Below: 3D skeletal reconstruction by Julia Molnar, missing just the final head (I find this very funny; Daffy Duck-esque) which we scaled to the fossil’s dimensions from the better data in our Archaeopteryx images. Yixianornis reconstruction There is also the concern, which the reviewers didn’t focus on but I could see other colleagues worrying about, that some of the specimens we used were either composites, sculpted, or otherwise not based on 100% complete, perfectly intact specimens. The latter are hard to come by for a diversity of extinct animals, especially in the maniraptoran/early bird group. We discussed some of these problems in our 3D Tyrannosaurus paper. The early dinosauromorph Marasuchus that we used was a cast/sculpted NHMUK specimen based on original material, as was our Coelophysis, Microraptor and Archaeopteryx; and our Carnegie ??Caenagnathus??Anzu (now published) specimen was based more on measurements from 1 specimen than from direct scans, and there were a few other issues with our other specimens, all detailed in our paper’s Supplementary Information.

But our intuition, based on a lot of time spent with these models and the analysis of their data, is that these anatomical imperfections matter far, far less than the statistical methods that we employed– because we add a lot of flesh (like real animals have!) outside of the skeleton in our method, the precise morphology of the skeleton doesn’t matter much. It’s not like you need the kind of quality of anatomical detail that you need to do systematic analyses or osteological descriptive papers. The broad dimensions can matter, but those tend to be covered by the (overly, we suspect) broad error bars that our study had (see graph above). Hence while anyone could quibble ad infinitum about the accuracy of our skeletal data, I doubt it’s that bad– and it’s still a huge leap beyond previous studies, which did not present quantitative data, did not do comparative studies of multiple species, or did not construct models based on actual 3D skeletons as opposed to artists’ 2D shrinkwrapped reconstructions (the “Greg Paul method”). We also did directly measure the bodies of two extant archosaurs in our paper: a freshwater crocodile and a junglefowl (CT scan of the latter is reconstructed below in 3D).

One thing we still need to do, in future studies, is to look more carefully inside of the bird clade (Aves/Avialae) to see what’s going on there, especially as one moves closer to the crown group (modern birds). We represented modern birds with simply 1 bird: the “wild-type chicken” Red junglefowl, which isn’t drastically different in body shape from other basal modern birds such as a tinamou. Our paper was not about how diversity of body shape and centre of mass evolved within modern birds. But inspecting trends within Palaeognathae would be super interesting, because a lot of locomotor, size and body shape changes evolved therein; ostriches are probably a very, very poor proxy for the size and shape of the most recent common ancestor of all extant birds, for example, even though they seem to be fairly basal within that whole lineage. And, naturally, our study opens up opportunities for anyone to add feathers to our models and investigate aerodynamics, or to apply our methods to other dinosaur/vertebrate/metazoan groups. If the funding gods are kind to us, later this year we will be looking more closely, in particular, at the base of Archosauria and what was happening to locomotor mechanics in Triassic archosaurs…

Clickum to embiggum:

Australian freshwater crocodile, Crocodylus johnstoni; we CT scanned it in 3 pieces.

Australian freshwater crocodile, Crocodylus johnstoni; we CT scanned it in 3 pieces while visiting the Witmer lab in Ohio.

A Red junglefowl cockerel, spotted in Lampang, Thailand during one of my elephant gait research excursions there. Svelte, muscular and fast as hell.

A Red junglefowl cockerel, spotted in Lampang, Thailand during one of my elephant gait research excursions there. Svelte, muscular and fast as hell. This photo is here to remind me to TAKE BLOODY PICTURES OF MY ACTUAL RESEARCH SPECIMENS SO I CAN SHOW THEM!

I’d bore you with the statistical intricacies of the paper, but that’s not very fun and it’s not the style of this blog, which is not called “What’s in John’s Software Code?”. Viv really worked his butt off to get the stats right, and we did many rounds of revisions and checking together, in addition to consultations with statistics experts. So I feel we did a good job. See the paper if that kind of thing floats your boat. Someone could find a flaw or alternative method, and if that changed our major conclusions that would be a bummer– but that’s science. We took the plunge and put all of our data online, as noted above, so anyone can do that, and that optimizes the reproducibility of science.

What I hope people do, in particular, is to use the 3D graphics of our paper’s 17 specimen-based archosaur bodies for other things– new and original research, video games, animations, whatever. It has been very satisfying to finally, from fairly early in the paper-writing process onwards, present all of the complex data in an analysis like this so someone else can use it. My past modelling papers have not done this, but I aim to backtrack and bring them up to snuff like this. We couldn’t publish open access in Nature, but we achieved reasonably open data at least, and to me that’s as important. I am really excited at a personal level, and intrigued from a professional standpoint, to see how our data and tools get used. We’ll be posting refinements of our (Matlab software-based) tools, which we’re still finding ways to enhance, as we proceed with future research.

Velociraptor-model-min Dilophosaurus-model-min00

Above: Two of the 17 archosaur 3D models (the skinny “mininal” models; shrinkwrapped for your protection) that you can download and examine and do stuff with! Dilophosaurus on the left; Velociraptor on the right. Maybe you can use these to make a Jurassic Park 4 film that is better, or at least more scientifically accurate, than Hollywood’s version! ;-) Just download free software like Meshlab, drop the OBJ files in and go!

Now, to bring the story full circle, the paper is out at last! A 4 year journey from Viv’s PhD thesis to the journal, and for me a ~14 year journey from my mind’s eye to realization. Phew! The real fun begins now, as we see how the paper is received! I hope you like it, and if you work in this area I hope you like the big dataset that comes with it, too. Perhaps more than any other paper I’ve written, because of the long voyage this paper has taken, it has a special place in my heart. I’m proud of it and the work our team did together to produce it. Now it is also yours. And all 3200ish words of this lengthy blog post are, as well!

Last but not least, enjoy the wonderful digital painting that Luis Rey did for this paper (another of my team’s many failed attempts to get on the cover of a journal!); he has now blogged about it, too!

Dinosaur posture and body shape evolving up the evolutionary tree, with example taxa depicted.

Dinosaur posture and body shape evolving up the evolutionary tree, with example taxa depicted. By Luis Rey.

 


News stories about this paper will be added below as they come out, featuring our favourites:

1) NERC’s Planet Earth, by Harriet Jarlett: “Dinosaur body shape changed the way birds stand

2) Ed Yong on Phenomena: “Crouching  bird, hidden dinosaur

3) Charles Choi on Live Science: “Crouching bird, hidden evolutionary purpose?

4) Brian Handwerk on Nat Geo Daily News: “Birds’ “Crouching” Gait Born in Dinosaur Ancestors

5) Jennifer Viegas on Discovery News: “Heavier dino arms led evolution to birds

6) Puneet Kollipara on Science News: “Birds may have had to crouch before they could fly

And some superb videos- we’re really happy with these:

1) Nature’s “Crouching Turkey, Hidden Dragon

2) Reuters TV’s “3D study shows forelimb enlargement key to evolution of dinosaurs into birds

Synopsis: Decent coverage, but negligible coverage in the general press; just science-specialist media, more or less. I think the story was judged to be too complex/esoteric for the general public. You’d think dinosaurs, evolution, computers plus physics would be an “easy sell” but it was not, and I don’t think we made any big errors “selling” it. Interesting– I continue to learn more about how unpredictable the media can be.

Regardless, the paper has had a great response from scientist colleagues/science afficionados, which was the target audience anyway. I’m very pleased with it, too– it’s one of my team’s best papers in my ~18 year career.

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