Feeds:
Posts
Comments

Posts Tagged ‘evolution’

(Marcela with some furry friends; photo by Oliver Siddon)

(Marcela with some felid friends; photo by Oliver Siddon)

A guest post by Marcela Randau (m.randau@ucl.ac.uk)

Stomach-Churning Rating: 1/10; just bones and data plots!

It is often said that all cats are very similar in terms of their skeletal morphology (“a cat is a cat is a cat”). But is this really the case? It may be if only gross, qualitative anatomy is taken into consideration, i.e., if you just eyeball the skeletons of tigers and lions you might find yourself not knowing which one is which. But with huge advances in technology that allows for extracting detailed shape information off a structure (e.g., a skull) and for analysing this information (‘Geometric Morphometrics’), it has become more and more possible to distinguish between relatively similar forms – which may be from distinct species, separate sexes, or even just different populations of the same taxon.

And it is reasonable to think that cat skeletons might be a lot more different than what meets the eye, as for a lineage of apparently similarly built animals, with not that much variation in diet  (all cats are hypercarnivores) there is substantial variation in body mass (over 300-fold just in living species!) and in ecology across cat species. From the cursorial cheetah to the arboreal clouded leopard, felids present a wide range of locomotory adaptations. Yes, all cats can climb, but some do it better than others: think lion versus margay (yes, they do descend trees head-first). As hypercarnivores, all cats are meat specialists, but they also change with regards to how big their prey is, with a general and sometimes-not-so-black-and-white three-tier classification into small, mixed and large prey specialists. The rule of thumb is ‘if you are lighter than ~20-25 kg, hunt small stuff. If you are heavier than that, hunt BIG BIG things; bigger than yourself. And if you are in the middle ground, hunt some small-ish things, some big-ish things, and things about your size. Well, -ish’ – their prey size preference has a lot to do with energetic constraints (have a look at Carbone et al. 1999; and Carbone et al. 2007, if you’re interested in this). But the fun bit here is that form sometimes correlates quite strongly with function, so we should be able to find differences in some of their bones that carry this ecological signal.

Indeed, for a while now, we have known that the shape of the skull and limbs of felids can tell us a lot about how they move and how big their prey is (Meachen-Samuels and Van Valkenburgh 2009, 2009), but a large proportion of their skeleton has been largely ignored: we don’t know half as much about ecomorphology and evolution of the vertebral column. Well, it was time we changed this a bit! As the PhD student in the Leverhulme-funded ‘Walking the cat back’ (or more informally, “Team Cat”) project, I’ve spend a big chunk of my first two years travelling around the world (well, ok, mainly to several locations in the USA) carrying a heavy pellet case containing my working tool, a Microscribe, to collect 3-D landmarks (Fig. 1) across the presacral vertebral column of several cat species. And some of first results are just out! Check them out by reading our latest paper, “Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories” in the Organisms Diversity and Evolution journal (Randau, Cuff, et al. 2016).

cheetah-verts

Fig. 1: Different vertebral morphologies and their respective three-dimensional landmarks. Vertebral images are from CT scans of Acinonyx jubatus (Cheetah, USNM 520539)

Building from results based on our linear vertebral data from the beginning of the year (Randau, Goswami, et al. 2016), the 3-D vertebral coordinates carry a lot more information and we were able to describe how this complex shape-function relationship takes place throughout the axial skeleton (in cats at least) in much better detail than our prior study did. One of the difficulties in studying serial structures such as the vertebral column is that some clades present variation in vertebral count which makes it less straightforward to compare individual vertebrae or regions across species. However, mammals are relatively strongly constrained in vertebral count, and Felidae (cats; living and known fossils) show no variation at all, having 27 presacral vertebrae. So adaptation of the axial skeleton in mammals has been suggested to happen by modification of shape rather than changes in vertebral number.

Using a variety of geometric morphometric analyses, under a phylogenetically informative methodology, we have shown that there is clear shape and functional regionalisation across the vertebral column, with vertebrae forming clusters that share similar signal. Most interestingly, the big picture of these results is a neck region which is either very conservative in shape, or is under much stronger constraints preventing it from responding to direct evolutionary pressures, contrasting with the ‘posteriormost’ post-diaphragmatic tenth thoracic (T10) to last lumbar (L7) vertebral region, which show the strongest ecological correlations.

We were able to analyse shape change through functional vertebral regions, rather than individual vertebrae alone, by making a novel application of a technique called the ‘Phenotypic Trajectory Analysis’, and demonstrated that the direction of vertebral shape trajectories in the morphospace changes considerably between both prey size and locomotory ecomorphs in cats, but that the amount of change in each group was the same. It was again in this T10-L7 region that ecological groups differed the most in vertebral shape trajectories (Fig. 2).

pta-cats

Figure 2: Phenotypic trajectory analysis (PTA) of vertebrae in the T10 – L7 region grouped by prey size (A) and locomotory (B) categories.

So in the postcranial morphology of cats can be distinguished, changing its anatomy in order to accommodate the different lifestyles we see across species. But the distinct parts of this structure respond to selection differently. The next step is figuring out how that might happen and we are working on it.

While Team Cat continues to investigate other biomechanical and evolutionary aspects of postcranial morphology in this interesting family, we’ve been able to discuss some of these and other results in a recent outreach event organised by the University College of London Grant Museum of Zoology and The Royal Veterinary College. We called it “Wild Cats Uncovered: movement evolves”. Check how it went here: (https://blogs.ucl.ac.uk/museums/2016/11/17/cheetah-post-mortem/) and here (http://www.rvc.ac.uk/research/research-centres-and-facilities/structure-and-motion/news/wild-cats-uncovered), with even more pics here (https://www.flickr.com/photos/144824896@N07/sets/72157676695634065/).

References used here:

Carbone, C., Mace, G. M., Roberts, S. C., and Macdonald, D. W. 1999. Energetic constaints on the diet of terrestrial carnivores. Nature 402:286-288.

Carbone, C., Teacher, A., and Rowcliffe, J. M. 2007. The costs of carnivory. PLoS biology 5 (2):e22.

Meachen-Samuels, J. and Van Valkenburgh, B. 2009. Craniodental indicators of prey size preference in the Felidae. Biol J Linn Soc 96 (4):784-799.

———. 2009. Forelimb indicators of prey-size preference in the Felidae. Journal of morphology 270 (6):729-744.

Randau, M., Cuff, A. R., Hutchinson, J. R., Pierce, S. E., and Goswami, A. 2016. Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories. Organisms Diversity and Evolution Online First.

Randau, M., Goswami, A., Hutchinson, J. R., Cuff, A. R., and Pierce, S. E. 2016. Cryptic complexity in felid vertebral evolution: shape differentiation and allometry of the axial skeleton. Zoological Journal of the Linnean Society 178 (1):183-202.

Read Full Post »

Short post here– I have 4 jobs now opened on my team, 1 short-term one (~4 months or less) and 3 long-term ones (5 years; negotiable down to 2-3 minimum) as follows:

Stomach-Churning Rating: -10/10 Let’s do some SCIENCE!

  1. Research Technician in Vertebrate Anatomical Imaging; until ~1 December 2016 (some flexibility), on our Leverhulme Trust sesamoid bone grant. Lots of flexibility here and on a super fun, established project! Deadline to apply: 11 August (interviews will be 22 August)
  2. Part-time (50%) Research Administrator, on our ERC dinosaur evolution/locomotion grant until 2021. I’m hunting for someone that’s super organized and enthusiastic and not afraid of paperwork (it is EU funding, after all), but there is sure to be some involvement in science communication, too. Deadline to apply: 11 August  (interviews will be 31 August)
  3. Research Technician in Biomechanics; until 2021 as above. This post will not “just” be technical support but hands-on doing science. Some vital experience in biomechanics will be needed as the research will begin very quickly after starting. If the right person applies, we could agree for them to do a part-time PhD or MRes related to the grant research (but that’s not guaranteed in advance). Deadline to apply: 26 August (interviews will be 7/8 September)
  4. Postdoctoral Researcher in Biomechanics; until 2021 as above. This second postdoc on the project will join Dr. Vivian Allen and the rest of my team to push this project forward! I am keenest on finding someone who is good at biomechanical computer simulation, i.e., has already published on work in that general area. But the right person with XROMM (digital biplanar fluoroscopy), other digital imaging and biomechanics experience might fit. Deadline to apply: 23 August (interviews will be 7/8 September)

Update: all jobs have closed for applications.

Update 2: BUT not all the jobs are 5-year contracts. Some may open up again for new people in the future (but not very soon). Stay tuned…

Note that on the bottom of each page linked above, there are Person Specification and Job Description documents that explain more what the jobs are about and what skills we’re looking for in applicants. I strongly encourage any applicants to read these before applying. If those documents don’t describe you reasonably well, it is probably best not to apply, but you can always contact me if you’re not sure.

The project for jobs 2-4 is about testing the “locomotor superiority hypothesis”, an old idea that dinosaurs gained dominance in the Triassic-Jurassic transition because something about their locomotion was better in some way than other archosaurs’. That idea has been dismissed, embraced, ignored and otherwise considered by various studies over the past 40+ years but never really well tested. So in we go, with a lot of biomechanical and anatomical tools and ideas to try to (indirectly) test it! As usual for projects that I do, there is a healthy mix of empirical (e.g. experiments) and theoretical (e.g. models/simulations) research to be done.

Please spread the word if you know of someone right for any of these roles. I am casting a broad net. The next year (and beyond) is going to be a very exciting time on my team, with this big ~£1.9M ERC Horizon 2020 grant starting and lots of modelling, simulation, experiments, imaging and more. Non-EU/EEA/UK people are very welcome to apply– “Brexit” is not expected to affect this project. If you’re not familiar with my team, check out my “mission statement” for what we stand for professionally and as a team. Join us!

Read Full Post »

Happy Darwin Day from the frozen tundra sunny but muddy, frosty lands of England! I bring you limb muscles as peace offerings on this auspicious day. Lots of limb muscles. And a new theme for future blog posts to follow up on: starting off my “Better Know A Muscle” (nod to Stephen Colbert; alternative link) series. My BKAM series intends to walk through the evolutionary history of the coolest (skeletal/striated) muscles. Chuck Darwin would not enjoy the inevitable blood in this photo-tour, but hopefully he’d like the evolution. Off we go, in search of better knowledge via an evolutionary perspective!

There is, inarguably, no cooler muscle than M. caudofemoralis longus, or CFL for short. It includes the largest limb muscles of any land animal, and it’s a strange muscle that confused anatomists for many years– was it a muscle of the body (an axial or “extrinsic” limb muscle, directly related to the segmented vertebral column) or of the limbs (an “abaxial” muscle, developing with the other limb muscles from specific regions of the paraxial mesoderm/myotome, not branching off from the axial muscles)? Developmental biologists and anatomists answered that conclusively over the past century: the CFL is a limb muscle, not some muscle that lost its way from the vertebral column and ended up stranded on the hindlimb.

The CFL is also a muscle that we know a fair amount about in terms of its fossil record and function, as you may know if you’re a dinosaur fan, and as I will quickly review later. We know enough about it that we can even dare to speculate if organisms on other planets would have it. Well, sort of…

Stomach-Churning Rating: 8/10. Lots of meaty, bloody, gooey goodness, on and on, for numerous species. This is an anatomy post for those with an appetite for raw morphology.

Let’s start from a strong (and non-gooey) vantage point, to which we shall return. The CFL in crocodiles and most other groups is (and long was) a large muscle extending from much of the front half or so of the tail to the back of the femur (thigh bone), as shown here:

Julia Molnar's fabulous illustration of Alligator's limb muscles, from our 2014 paper in Journal of Anatomy.

Julia Molnar’s fabulous illustration of Alligator‘s limb muscles, from our 2014 paper in Journal of Anatomy. Note the CFL in blue at the bottom right.

As the drawing shows, the CFL has a friend: the CFB. The CFB is a shorter, stumpier version of the CFL restricted to the tail’s base, near the hip. The “B” in its name means “brevis”, or runty. It gets much less respect than its friend the CFL. Pity the poor CFB.

But look closer at the CFL in the drawing above and you’ll see a thin blue tendon extending past the knee to the outer side of the lower leg. This is the famed(?) “tendon of Sutton“, or secondary tendon of the CFL. So the CFL has two insertions, one on the femur and one (indirectly) onto the shank. More about that later.

Together, we can talk about these two muscles (CFL and CFB) as the caudofemoralis (CF) group, and the name is nice because it describes how they run from the tail (“caudo”) to the femur (“femoralis”). Mammal anatomists were late to this party and gave mammal muscles stupidly unhelpful names like “gluteus” or “vastus” or “babalooey”. Thanks.

But enough abstract drawings, even if they rock, and enough nomenclature. Here is the whopping big CFL muscle of a real crocodile:

Huge Nile crocodile, but a relatively small CFL.

Huge Nile crocodile, but a relatively small CFL.

Bigger crocs have smaller legs and muscles.

Bigger crocs have smaller legs and thus smaller leg muscles, relatively speaking. CFL at the top, curving to the left.

The giant Nile croc's CFL muscle removed for measurements.

The giant Nile croc’s CFL muscle removed for measurements. 2.35 kg of muscle! Not shabby for a 278 kg animal.

However, maybe crocodile and other archosaur CFL muscles are not “average” for leggy vertebrates? We can’t tell unless we take an evolutionary tack to the question.

Where did the CFL come from, you may ask? Ahh, that is shrouded in the fin-limb transition‘s mysteries. Living amphibians such as salamanders have at least one CF muscle, so a clear predecessor to the CFL (and maybe CFB) was present before reptiles scampered onto the scene.

But going further back through the CF muscles’ history, into lobe-finned fish, becomes very hard because those fish (today) have so few fin muscles that, in our distant fishy ancestors, would have given rise eventually to the CF and other muscle groups. With many land animals having 30+ hindlimb muscles, and fish having 2-8 or so, there obviously was an increase in the number of muscles as limbs evolved from fins. And because a limb has to do lots of difficult three-dimensional things on land while coping with gravity, more muscles to enable that complex control surely were needed.

OK, so there were CF muscles early in tetrapod history, presumably, anchored on that big, round fleshy tail that they evolved from their thin, finned fishy one — but what happened next? Lizards give us some clues, and their CFL muscles aren’t all that different from crocodiles, so the CFL’s massive size and secondary “tendon of Sutton” seems to be a reptile thing, at least.

Courtesy of Emma Schachner, a large varanid lizard's very freshly preserved CFL and other hindlimb muscles.

Courtesy of Emma Schachner, a large varanid lizard’s very freshly preserved CFL and other hindlimb muscles.

Courtesy of Emma Schachner, zoomed in on the tendons and insertions of the CFL muscle and others.

Courtesy of Emma Schachner, zoomed in on the tendons and insertions of the CFL muscle and others. Beautiful anatomy there!

Looking up at the belly of a basilisk lizard and its dissected right leg, with the end of the CFL labelled.

Looking up at the belly of a basilisk lizard and its dissected right leg, with the end of the CFL labelled. It’s not ideally dissected here, but it is present.

An unspecified iguanid(?) lizard, probably a juvenile Iguana iguana, dissected and showing its CFL muscle at its end. The muscle would extemd about halfway down the tail, though.

An unspecified iguanid(?) lizard, probably a juvenile Iguana iguana, dissected to reveal its CFL muscle near its attachment to the femur. The muscle would extend further, about halfway down the tail, though.

Let’s return to crocodiles, for one because they are so flippin’ cool, and for another because they give a segue into archosaurs, especially dinosaurs, and thence birds:

A moderate-sized (45kg) Nile crocodile with its CFL muscle proudly displayed.

A moderate-sized (45kg) Nile crocodile with its CFL muscle proudly displayed. Note the healthy sheath of fat (cut here) around the CFL.

American alligator's CFL dominates the photo. Photo by Vivian Allen.

American alligator’s CFL dominates the photo [by Vivian Allen].

Black caiman, Melanosuchus, showing off its CFL muscle (pink "steak" in the middle of the tail near the leg).

Black caiman, Melanosuchus, showing off its CFL muscle (pink “steak” in the middle of the tail near the leg), underneath all that dark armour and fatty superficial musculature.

A closer look at the black caiman's thigh and CFL muscle.

A closer look at the black caiman’s thigh and CFL muscle.

Like I hinted above, crocodiles (and the anatomy of the CFL they share with lizards and some other tetrapods) open a window into the evolution of unusual tail-to-thigh muscles and locomotor behaviours in tetrapod vertebrates.

Thanks in large part to Steve Gatesy’s groundbreaking work in the 1990s on the CFL muscle, we understand now how it works in living reptiles like crocodiles. It mainly serves to retract the femur (extend the hip joint), drawing the leg backwards. This also helps support the weight of the animal while the foot is on the ground, and power the animal forwards. So we call the CFL a “stance phase muscle”, referring to how it mainly plays a role during ground contact and resisting gravity, rather than swinging the leg forwards (protracting the limb; i.e. as a “swing phase muscle”).

The “tendon of Sutton” probably helps to begin retracting the shank once the thigh has moved forward enough, facilitating the switch from stance to swing phase, but someone really needs to study that question more someday.

And thanks again to that same body of work by Gatesy (and some others too), we also understand how the CFL’s anatomy relates to the underlying anatomy of the skeleton. There is a large space for the CFL to originate from on the bottom of the tail vertebrae, and a honking big crest (the fourth trochanter) on the femur in most reptiles that serves as the major attachment point, from which the thin “tendon of Sutton” extends down past the knee.

Femur bones (left side) from an adult ostrich (Left) and Nile crocodile (Right).

Femur bones (left side; rear view) from an adult ostrich (left) and Nile crocodile (right). Appropriate scale bar is appropriate. The fourth trochanter for the CFL is visible in the crocodile almost midway down the femur. Little is left of it in the ostrich but there is a bumpy little muscle scar in almost the same region as the fourth trochanter, and this is where the same muscle (often called the CFC; but it is basically just a small CFL) attaches.

That relationship of the CFL’s muscular anatomy and the underlying skeleton’s anatomy helps us a lot! Now we can begin to look at extinct relatives of crocodiles; members of the archosaur group that includes dinosaurs (which today we consider to include birds, too), and things get even more interesting! The “tendon of Sutton”, hinted at by a “pendant” part of the fourth trochanter that points down toward the knee, seems to go away multiple times within dinosaurs. Bye bye! Then plenty more happens:

A large duckbill dinosaur's left leg, with a red line drawn in showing roughly where the CFL would be running, to end up at the fourth trochanter. Many Mesozoic dinosaurs have skeletal anatomy that indicates a similar CFL muscle.

A large duckbill dinosaur’s left leg, with a red line drawn in showing roughly where the CFL would be running, to end up at the fourth trochanter. Many Mesozoic dinosaurs have skeletal anatomy that indicates a similar CFL muscle.

We can even go so far as to reconstruct the 3D anatomy of the CFL in a dinosaur such as T. rex ("Sue" specimen here; from Julia Molnar's awesome illustration in our 2011 paper), with a fair degree of confidence.

We can even go so far as to reconstruct the 3D anatomy of the CFL in a dinosaur such as T. rex (“Sue” specimen here; from Julia Molnar’s awesome illustration as part of our 2011 paper), with a fair degree of confidence. >180kg steak, anyone?

As we approach birds along the dinosaur lineage, the tail gets smaller and so does the fourth trochanter and thus so must the CFL muscle, until we’re left with just a little flap of muscle, at best. In concert, the hindlimbs get more crouched, the forelimbs get larger, flight evolves and voila! An explosion of modern bird species!

Ozburt (72)

Left femur of an ostrich in side view (hip is toward the right side) showing many muscles that attach around the knee (on the left), then the thin strap of CF muscle (barely visible; 2nd from the right) clinging near the midshaft of the femur.

Another adult ostrich's CF muscle complex, removed for study.

Another adult ostrich’s CF muscle complex, removed for study. Not enough ostrich myology for you yet? Plenty more in this old post! Or this one! Or this one… hey maybe I need to write less about ostriches? The CF muscle complex looks beefy but it’s no bigger than any other of the main hindlimb muscles, unlike the CFL in a crocodile or lizard, which puts everything else to shame!

STILL not enough ostrich for you yet? Take a tour of the major hindlimb muscles in this video:

And check out the limited mobility of the hip joint/femur here. No need for much femur motion when you’re not using your hip muscles as much to drive you forwards:

But I must move on… to the remainder of avian diversity! In just a few photos… Although the CF muscles are lost in numerous bird species, they tend to hang around and just remain a long, thin, unprepossessing muscle:

Chicken's right leg in side view. CFC (equivalent of CFL) muscle outlined and labelled.

Chicken’s right leg in side view. CFC muscle (equivalent of CFL; the ancestral CFB is confusingly called the CFP in birds, as it entirely resides on the pelvis) outlined and labelled.

A jay (species?) dissected to show some of the major leg muscles, including the CF. Photo by Vivian Allen.

A jay (species? I forget) dissected to show some of the major leg muscles, including the CFL-equivalent muscle; again, smallish. [Photo by Vivian Allen]

Finally, what’s up with mammals‘ tail-to-thigh CF-y muscles? Not much. Again, as in birds: smaller tail and/or femur, smaller CF muscles. Mammals instead depend more on their hamstring and gluteal muscles to support and propel themselves forward.

But many mammals do still have something that is either called the M. caudofemoralis or is likely the same thing, albeit almost always fairly modest in size. This evolutionary reduction of the CF muscle along the mammal (synapsid) lineage hasn’t gotten nearly as much attention as that given to the dinosaur/bird lineage’s CFL. Somebody should give it a thoroughly modern phylogenetic what-for! Science the shit outta that caudofemoralis…

Yet, oddly, to give one apparent counter-example, cats (felids) have, probably secondarily, beefed up their CF muscle a bit:

Cats have a pretty large CF muscle in general, and this jaguar is no exception! But mammals still tend to have fairly wimpy tails and thus CF muscles, or they even lose them (e.g. us?).

Cats have a pretty large CF muscle in general, and this jaguar is no exception! But mammals still tend to have fairly wimpy tails and thus CF muscles, or they even lose them (e.g. us?). [photo by Andrew Cuff, I think]

In summary, here’s what happened (click to embeefen):

Better Know A Muscle: The Evolution of M. caudofemoralis (longus)

Better Know A Muscle: the evolution of M. caudofemoralis (longus).

I hope you enjoyed the first BKAM episode!
I am willing to hear requests for future ones… M. pectoralis (major/profundus) is a serious contender.

P.S. It was Freezermas this week! I forgot to mention that. But this post counts as my Freezermas post for 2016; it’s all I can manage. Old Freezermas posts are here.

Read Full Post »

Seeking adaptations for running and swimming in the vertebral columns of ancient crocs

A guest post by Dr. Julia Molnar, Howard University, USA (this comes from Julia’s PhD research at RVC with John & colleagues)

Recently, John and I with colleagues Stephanie Pierce, Bhart-Anjan Bhullar, and Alan Turner described morphological and functional changes in the vertebral column with increasing aquatic adaptation in crocodylomorphs (Royal Society Open Science, doi 10.1098/rsos.150439). Our results shed light upon key aspects of the evolutionary history of these under-appreciated archosaurs.

Stomach-Churning Rating: 5/10; a juicy croc torso in one small photo but that’s all.

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

As fascinating as modern crocodiles might be, in many ways they are overshadowed by their extinct, Mesozoic cousins and ancestors. The Triassic, Jurassic, and early Cretaceous periods saw the small, fast, hyper-carnivorous “sphenosuchians,” the giant, flippered marine thalattosuchians, and various oddballs like the duck-billed Anatosuchus and the aptly named Armadillosuchus. As palaeontologists/biomechanists, we looked at this wide variety of ecological specializations in those species, the Crocodylomorpha, and wanted to know, how did they do it?

Of course, we weren’t the first scientists to wonder about the locomotion of crocodylomorphs, but we did have some new tools in our toolbox; specifically, a couple of micro-CT scanners and some sophisticated imaging software. We took CT and micro-CT scans of five fossil crocodylomorphs: two presumably terrestrial early crocodylomorphs (Terrestrisuchus and Protosuchus), three aquatic thalattosuchians (Pelagosaurus, Steneosaurus, and Metriorhynchus) and a semi-aquatic modern crocodile (Crocodylus niloticus). Since we’re still stuck on vertebrae (see, e.g., here; and also here), we digitally separated out the vertebrae to make 3D models of individual joints and took measurements from each vertebra. Finally, we manipulated the virtual joint models to find out how far they could move before the bones bumped into each other or the joints came apart (osteological range of motion, or RoM).

 

Our methods: get fossil, scan fossil, make virtual fossil and play with it.

Our methods: get fossil (NHMUK), scan fossil, make virtual fossil and play with it.

Above: Video of a single virtual inter-vertebral joint from the trunk of Pelagosaurus typus (NHMUK) showing maximum osteological range of motion in the lateral direction (video). Note the very un-modern-croc-like flat surfaces of the vertebral bodies! (modern crocs have a ball-and-socket spinal joint with the socket on the front end)

While this was a lot of fun, what we really wanted to find out was whether, as crocodylomorphs became specialized for different types of locomotion, the shapes of their vertebrae changed similarly to those of mammalian lineages. For example, many terrestrial mammals have a lumbar region that is very flexible dorsoventrally to allow up-and-down movements during bounding and galloping. Did fast-running crocodylomorphs have similar dorsoventral flexibility? And did fast-swimming aquatic crocodylomorphs evolve a stiffer vertebral column like that of whales and dolphins?

Above: Video of how we modelled and took measurements from the early crocodylomorph Terrestrisuchus gracilis (NHMUK).

Our first results were puzzling. The Nile croc had greater RoM in side-to-side motions, which makes sense because crocodiles mostly use more sprawling postures and are semi-aquatic, using quite a bit of side-to-side motions in life. The part that didn’t make sense was that we found pretty much the same thing in all of the fossil crocodylomorphs, including the presumably very terrestrial Terrestrisuchus and Protosuchus. With their long limbs and hinge-like joints, these two are unlikely to have been sprawlers or swimmers!

So we started looking for other parts of the croc that might affect RoM. The obvious candidate was osteoderms, the bony scales that cover the back. We went back to John’s Freezer and got out a nice frozen crocodile to measure the stiffness of its trunk and found that, sure enough, it was a lot stiffer and less mobile without the osteoderms. If the fairly flexible arrangement of osteoderms in crocodiles had this effect on stiffness, it seemed likely that (as previous authors have suggested; Eberhard Frey and Steve Salisbury being foremost amongst them) the rigid, interlocking osteoderms running from head to tail in early crocodylomorphs would really have put the brakes on their ability to move their trunk in certain ways.

Testing stiffness of crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated.

Testing the stiffness of (Nile) crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated. Click to em-croccen.

Another cool thing we found was new evidence of convergent evolution to aquatic lifestyles in the spines of thalattosuchians. The more basal thalattosuchians, thought to have been near-shore predators, had stiffness and RoM patterns similar to Crocodylus. But Metriorhynchus, which probably was very good at chasing down fast fish in the open ocean, seems to have had greater stiffness. (The stiffness estimates come from morphometrics and are based on modern crocodiles; see here again, or just read the paper already!) A stiff vertebral column can be useful for a swimmer because it increases the body’s natural frequency of oscillation, and faster oscillation means faster swimming (think tuna, not eel). The same thing seems to have happened in other secondarily aquatic vertebrate lineages such as whales, ichthyosaurs, and mosasaurs.

So, our results were a mixed bag of adaptations particular to crocs and ones that seem like general vertebrate swimming specializations. Crocodylomorphs are important because they are the only group of large vertebrates other than mammals that has secondarily aquatic members and has living members with a reasonably similar body plan, allowing us to test hypotheses in ways that would arguably be impossible for, say, non-avian dinosaurs and birds. The take-home message: crocodylomorphs A) are awesome, and B) can teach us a lot about how vertebrates adapt to different modes of life.

Another take on this story is on our lab website here.

Read Full Post »

Like many people, I’ve sprung for a personal genomics service lately, in my case “23 and me“. There are deeper reasons for doing it, such as finding out anything more about the genetic basis of my health problems and getting my child advance warning if there’s evidence of heritable risks, but curiosity was a big part of the decision. And hey, as a palaeontology fan I want to know how much Neanderthal is in me, because that’s just cool how sexy our two species were together. Well, here’s what I found out! Part of my obligatory “What’s In John’s [X]” series…

Stomach-Churning Rating: 0/10 unless you hate genes, but that’s pretty futile if you do.

First off, let’s explore my evolutionary history within Homo sapiens:

ancestry

 

For the benefit of those that don’t want to screen-squint or click to emzoomen, I’m 99.9% European ancestry in terms of modern populations’ genomic similarity. I’m mostly Northern European, with around 3% Southern and <1% Eastern. The <0.1% West African and Native American ancestries (on my chromosomes 6 and 10, I discerned) are just a smidgen, but I’m still happy to hear of them. I like being a mutt, even if mostly (~69%) a British-Irish and French-German mutt. I expected to find a bit more Scandinavian vestiges in my genome than the 0.7%, based on what little I know of my genealogy, but the 25.5% “broadly Northern European” could cover that.

Like maternal haplogroups? Welcome to my clan, D2 (no relation to D-12…):

haplogroupD2

D2’s like to stalk Mammuthus columbi and run from Smilodon fatalis or terror-birds.

Paternal haplogroups (from my freezer-burned, shrivelled little Y chromosome) are fun, too! Especially R1a1a; it’s the hip haplogroup to hang with:

haplogroupR1a1aWe R1a1a’s enjoy the rich flavour of a Megaloceros giganteus.

All that slaughtering of megafauna and perusing phylogenies was tiring. How about we sing the song of my genome?

Well, modern people are boring, even the migratory ass-kicking Ice Age ones. What going on inside me, and outside of Homo sapien? Check it out:

Neanderthal_and_proud

Chest-thumping caveman dance ensues! This was the result that got me the most excited. I’m worthy of wearing this shirt! 95th percentile, W00T!

3.1%NeanderthalYEAH

(then I found out my wife has more Neanderthal, and I was deflated… no fair! LOLZ.)

So anyway, I’m not just a bland European (not that any human’s ancestry is likely “bland” anyhow). Sweet! The ancestry results alone were interesting enough to make me feel like I got my £125 worth.

How about genetic markers for funky traits?

traits

OK, no booze-flushing reaction or lactose issues, I knew that; bitter or asparagus tastes and smells, sure I knew that; blonde and blue-eyed: check; earwax: eew but kinda neat; sprinty muscles, that makes a lot of sense (I love to sprint; not so much endurance running)… baldness: thanks. Thanks a lot, ancestors! Nice try, curly-haired ur-Hutchinsons, but your coiffured efforts were for naught in my case.

Norovirus: OK I’ll try to avoid youse guys. Duly noted. I’m not a fan of vomiting, despite what my college friends might tell you if asked.

Caffeine “fast metabolizer”– hell yes! No doubt about that. I can take about 1 shot of Espresso in the morning and then I’m done; I’ve become extremely sensitive to caffeine. But the good news for that gene marker is that my alleles “didn’t increase subjects’ heart attack risk” with moderate caffeine intake, and indeed some coffee might even be prophylactic. I don’t intend to test that, though. My days of quaffing a pot of coffee before fraternity parties are long gone.

Overall, the traits stuff was intriguing but held no real surprises. “Subjects averaged 0.3 – 0.7 centimeters shorter than typical height” for one genetic marker is a good example, considering my altitudinally-enhanced morphology, of how genes aren’t necessarily simple determinants of fate.

With trepidation, I turn to genomic markers of my health tendencies:

genetics

Not much going on there. But wait… Looking closer…

Alz

D’oh. But not a big surprise; my mother died of Alzheimer’s so it was at least 50/50 for me. And still not a fate set in stone amino acids, but I’m more motivated now to live it up in my youth! There’s genetic destiny, genetic tendency, and then personal choice. I’ll do what I can with the latter.

Gene products can determine how we react to different chemicals, and I take my share, so I was keen to see what 23andme dug up. It was fascinating:

health

Without boring you with my prescription list, I’m sensitive to several hugely important drugs I take or have taken before. My GP doctor was keen to know this! I feel like this was worth the cost of the genome service to know all these caveats about my metabolism of pharmaceuticals.

So, that’s what I’ve found by rummaging around my genome. I’ve also used the ancestry tools in 23andme to find names of some 4th/5th cousins (who also did the 23andme genome service) around the eastern USA, which is where a lot of my ancestors settled in the 18th-19th centuries, I recall being told.

I don’t feel very worried about abuse of my genomic data by corporations, or other privacy issues related to this. Maybe I should. I feel like having my genome data in my possession, and likely insights 23andme or other services will give me using it in the future, are worth the risks.

If you’ve used a personal genome service of any kind and want to share your tales, go for it in the Comments!

Read Full Post »

Deck the ‘Nets With PeerJ Papers— please sing along!

♬Deck the ‘nets with PeerJ papers,
Fa la la la la, la la la la.
‘Tis the day to show our labours,
Fa la la la la, la la la la.

Downloads free; CC-BY license,
Fa la la, la la la, la la la.
Read the extant ratite science,
Fa la la la la, la la la la.

See the emu legs before you
Fa la la la la, la la la la.
Muscles allometric’ly grew.
Fa la la la la, la la la la.

Follow the evolvin’ kneecaps
Fa la la la la, la la la la.
While we dish out ratite recaps 
Fa la la la la, la la la la.

Soon ostrich patellar printing
Fa la la la la, la la la la.
Hail anat’my, don’t be squinting
Fa la la la la, la la la la.

Dissections done all together
Fa la la la la, la la la la.
Heedless of the flying feathers,
Fa la la la la, la la la la♪

(alternate rockin’ instrumental version)

Stomach-Churning Rating: 5/10: cheesy songs vs. fatty chunks of tissue; there are no better Crimbo treats!

Today is a special day for palaeognath publications, principally pertaining to the plethora of published PeerJ papers (well, three of them anyway) released today, featuring my team’s research! An early Crimbo comes this year in the form of three related studies of hind limb anatomy, development, evolution and biomechanics in those flightless feathered freaks of evolutionary whimsy, the ratites! And since the papers are all published online in PeerJ (gold open access), they are free for anyone with internet access to download and use with due credit. These papers include some stunning images of morphology and histology, evolutionary diagrams, and a special treat to be revealed below. Here I’ll summarize the papers we have written together (with thanks to Leverhulme Trust funding!):

1) Lamas, L., Main, R.P., Hutchinson, J.R. 2014. Ontogenetic scaling patterns and functional anatomy of the pelvic limb musculature in emus (Dromaius novaehollandiae). PeerJ 2:e716 http://dx.doi.org/10.7717/peerj.716 

My final year PhD student and “emu whisperer” Luis Lamas has published his first paper with co-supervisor Russ Main and I. Our paper beautifully illustrates the gross anatomy of the leg muscles of emus, and then uses exhaustive measurements (about 6524 of them, all done manually!) of muscle architecture (masses, lengths, etc.) to show how each of the 34 muscles and their tendons grew across a more than tenfold range of body mass (from 6 weeks to 18 months of age). We learned that these muscles get relatively, not just absolutely, larger as emus grow, and their force-generating ability increases almost as strongly, whereas their tendons tend to grow less quickly. As a result, baby emus have only about 22% of their body mass as leg muscles, vs. about 30% in adults. However, baby emus still are extremely athletic, more so than adults and perhaps even “overbuilt” in some ways.

This pattern of rapidly growing, enlarged leg muscles seems to be a general, ancestral pattern for living bird species, reflecting the precocial (more independent, less nest-bound), cursorial (long-legged, running-adapted) natural history and anatomy, considering other studies of ostriches, rheas, chickens and other species close to the root of the avian family tree. But because emus, like other ratites, invest more of their body mass into leg muscles, they can carry out this precocial growth strategy to a greater extreme than flying birds, trading flight prowess away for enhanced running ability. This paper adds another important dataset to the oft-neglected area of “ontogenetic scaling” of the musculoskeletal system, or how the locomotor apparatus adapts to size-/age-related functional/developmental demands as it grows. Luis did a huge amount of work for this paper, leading arduous dissections and analysis of a complex dataset.

Superficial layer of leg muscles in an emu, in right side view.

Superficial layer of leg muscles in an emu, in right side view. Click any image here to emu-biggen. The ILPO and IC are like human rectus femoris (“quads”); ILFB like our biceps femoris (“hams”); FL, GM and GL much like our fibularis longus and gastrocnemius (calf) muscles, but much much bigger! Or, perhaps FL stands for fa la la la la?

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grown than isometry (maintaining the same relative size), which is the dotted line at 1.0.

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grew than isometry (maintaining the same relative size), which is the dotted line at 1. The numbers above each data point are the # of individuals measured. Muscle names are partly above; the rest are in the paper. If you want to know them, we might have been separated at birth!

2) Regnault, S., Pitsillides, A.A., Hutchinson, J.R. 2014. Structure, ontogeny and evolution of the patellar tendon in emus (Dromaius novaehollandiae) and other palaeognath birds. PeerJ 2:e711 http://dx.doi.org/10.7717/peerj.711

My second year PhD student Sophie Regnault (guest-blogger here before with her rhino feet post) has released her first PhD paper, on the evolution of kneecaps (patellae) in birds, with a focus on the strangeness of the region that should contain the patella in emus. This is a great new collaboration combining her expertise in all aspects of the research with coauthor Prof. Andy Pitsillides‘s on tissue histology and mine on evolution and morphology. This work stems from my own research fellowship on the evolution of the patella in birds, but Sophie has taken it in a bold new direction. First, we realized that emus don’t have a patella– they just keep that region of the knee extensor (~human quadriceps muscle) tendon as a fatty, fibrous tissue throughout growth, showing no signs of forming a bony patella like other birds do. This still blows my mind! Why they do this, we can only speculate meekly about so far. Then, we surveyed other ratites and related birds to see just how unusual the condition in emus was. We discovered, by mapping the form of the patella across an avian family tree, that this fatty tendon seems to be a thing that some ratites (emus, cassowaries and probably the extinct giant moas) do, whereas ostriches go the opposite direction and develop a giant double-boned kneecap in each knee (see below), whereas some other relatives like tinamous and kiwis develop a more “normal”, simple flake-like bit of bone, which is likely the state that the most recent common ancestor of all living birds had.

There’s a lot in this paper for anatomists, biomechanists, palaeontologists, ornithologists, evo-devo folks and more… plenty of food for thought. The paper hearkens back to my 2002 study of the evolution of leg tendons in tetrapods on the lineage that led to birds. In that study I sort of punted on the question of how a patella evolved in birds, because I didn’t quite understand that wonderful little sesamoid bone. And now, 12 years later, we do understand it, at least within the deepest branches of living birds. What happened further up the tree, in later branches, remains a big open subject. It’s clear there were some remarkable changes, such as enormous patellae in diving birds (which the Cretaceous Hesperornis did to an extreme) or losses in other birds (e.g., by some accounts, puffins… I am skeptical)– but curiously, patellae that are not lost in some other birds that you might expect (e.g., the very non-leggy hummingbirds).

Fatty knee extensor tendon of emus, lacking a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing over it. A is a schematic; B is a dissection.

Fatty knee extensor tendon of an emu, showing the absence of a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing on over it. A is a schematic; B is a dissection.

Sectioning of a Southern Cassowary's knee extensor tendon, showing: A Similar section  as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, with collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Sectioning of a Southern Cassowary’s knee extensor tendon, showing: A, Similar section as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, With collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds, which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, black is a gigantic spar of bone in extinct Hesperornis and relatives, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds (Struthio down to Apteryx), which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

3) Chadwick, K.P., Regnault, S., Allen, V., Hutchinson, J.R. 2014. Three-dimensional anatomy of the ostrich (Struthio camelus) knee joint. PeerJ 2:e706 http://dx.doi.org/10.7717/peerj.706

Finally, Kyle Chadwick came from the USA to do a technician post and also part-time Masters degree with me on our sesamoid grant, and proved himself so apt at research that he published a paper just ~3 months into that work! Vivian Allen (now a postdoc on our sesamoid bone grant) joined us in this work, along with Sophie Regnault. We conceived of this paper as fulfilling a need to explain how the major tissues of the knee joint in ostriches, which surround the double-patella noted above, all relate to each other and especially to the patellae. We CT and MRI scanned several ostrich knees and Kyle made a 3D model of a representative subject’s anatomy, which agrees well with the scattered reports of ostrich knee/patellar morphology in the literature but clarifies the complex relationships of all the key organs for the first time.

This ostrich knee model also takes Kyle on an important first step in his Masters research, which is analyzing how this morphology would interact with the potential loads on the patellae. Sesamoid bones like the patella are famously responsive to mechanical loads, so by studying this interaction in ostrich knees, along with other studies of various species with and without patellae, we hope to use to understand why some species evolved patellae (some birds, mammals and lizards; multiple times) and why some never did (most other species, including amphibians, turtles, crocodiles and dinosaurs). And, excitingly for those of you paying attention, this paper includes links to STL format 3D graphics so you can print your own ostrich knees, and a 3D pdf so you can interactively inspect the anatomy yourself!

(A) X-ray of an ostrich knee in side view, and (B) labelled schematic of the same.

Ostrich knee in side view: A, X-ray, and (B) labelled schematic.

3D model of an ostrich knee, showing: A, view looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, view looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

3D model of an ostrich knee, showing: A, View looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, View looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

You can view all the peer review history of the papers if you want, and that prompts me to comment that, as usual at PeerJ (full disclosure: I’m an associate editor but that brings me £0 conflict of interest), the peer review quality was as rigorous at a typical specialist journal, and faster reviewing+editing+production than any other journal I’ve experienced. Publishing there truly is fun!

Merry Christmas and Happy Holidays — and good Ratite-tidings to all!

And stay tuned- the New Year will bring at least three more papers from us on this subject of ratite locomotion and musculoskeletal anatomy!

♬Should auld palaeognathans be forgot, 
And never brought for scans? 
Should publications be soon sought, 
For auld ratite fans!♪

Read Full Post »

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?

Read Full Post »

Older Posts »