Footprints in the sand

What comes to mind when you think about the Isle of Skye?

Chances are, it's one of three things.

The first is the stunningly beautiful scenery.  It's the largest of the Inner Hebrides, and is noted for its rugged, rocky hills, craggy coastline, and emerald-green meadows.

Sidney Richard Percy, Loch Coruisk (1874) [Image is in the Public Domain]

Second, history buffs will remember Skye as the place where "Bonnie Prince Charlie" (Charles Edward Stuart) fled, with the help of Flora MacDonald, after Scotland's devastating loss at the Battle of Culloden.  Stuart's repeated attempts afterward to claim the thrones of England and Scotland never came to much.  He died in exile in Rome in 1788 at the age of 67, depressed and miserable -- but even today, he remains a symbol to many Scots of "what might have been."

Third, if you're someone who likes to indulge in a wee dram on occasion, you probably know that it's home to the famous Talisker and Torabhaig distilleries, which produce absolutely fantastic single-malt whiskies.

I doubt, somehow, that many people would come up with a fourth thing that Skye should be famous for, and which was the subject of a paper in PLOS-One this week: it is one of the best sites for middle-Jurassic age fossils in the world.

167 million years ago, Scotland was about at the latitude of the Tropic of Cancer, and was a hot, lush swampy rainforest.  Prince Charles's Point -- the place where Bonnie Prince Charlie supposedly landed after making it safely "over the sea to Skye," in the words of the Skye Boat Song -- was a shallow, sandy-bottomed lagoon.

And it was home to some big dinosaurs.

The paper describes tracks by huge, long-necked sauropods like Cetiosaurus -- and those of the carnivorous theropods that hunted them, such as Megalosaurus.

A complete Cetiosaurus skeleton found near Rutland, England  [Image licensed under the Creative Commons Paul Stainthorp from United Kingdom, Cetiosaurus mount, CC BY-SA 2.0]

The Cetiosaurus tracks are as big around as car tires, and the study found individual trackways twelve meters long -- made, the researchers said, by dinosaurs ambling about, probably in search of the huge amounts of food it took to keep an animal that size going.

It's hard to imagine the rugged, windswept islands of the Hebrides like they were then -- something more like today's Florida Keys, and the home to the whole assemblage of mid-Mesozoic fauna.  Not only the big theropods and sauropods, such as the ones that left the footprints on the Isle of Skye, but pterodactyls flying overhead, and in the seas, the superficially dolphin-like icthyosaurs -- and the long-necked plesiosaurs that still come up in conversations about Loch Ness, only a hundred miles east as the Rhamphorhynchus flies.

"O Earth, what changes hast thou seen?" Tennyson mused -- "There, where the long road roars, has been the stillness of the central sea."  And those changes are still occurring.  The Atlantic Ocean is still progressively widening; a complex series of faults is making all of the Anatolian region twist counterclockwise; the "Horn of Africa" is rifting away from the rest of the continent and eventually will drift off into the Indian Ocean; Australia is on a collision course with Southeast Asia.  We humans leave our own footprints in the sand, but how ephemeral are they?  Will paleontologists 167 million years from now know of our presence, from traces left behind on whatever configuration the continents will then have?

It recalls the haunting lines from another poet, Percy Bysshe Shelley, which seems a fitting place to end:

I met a traveller from an antique land
Who said: Two vast and trunkless legs of stone
Stand in the desert.  Near them, on the sand,
Half sunk, a shattered visage lies, whose frown,
And wrinkled lip, and sneer of cold command,
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them, and the heart that fed.
And on the pedestal these words appear:
"My name is Ozymandias, King of Kings:
Look on my works, ye Mighty, and despair!"
Nothing beside remains.  Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.

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Dinosaur redux

For me, one of the coolest things about science is that even once you think you've got something pretty well figured out, you can always find new interesting pieces of the puzzle.

For example, take dinosaurs, which we've known a good bit about for a long while, starting with Mary Anning's discoveries along the "Jurassic Coast" of Dorset, England in the early nineteenth century.  Even the kids' books when I was growing up back in the 1960s and 1970s had a lot of pretty decent information.  Although some of the reconstructions of skeletons, and (especially) our knowledge of the soft tissue that covered it, has changed since that time, it wasn't like I had to completely relearn the science when I studied it more seriously.

That said, we're still learning new stuff and adding to the picture.  Just this week we had two new papers that have sharpened the focus on our understanding of dinosaur evolution -- the first about the mid-Jurassic peak in dinosaur diversity and size, and the second about the event that wiped the entire lineage out, with the exception of the ones we now call birds.

The first paper is from Proceedings of the Royal Society B, and is titled "Extinction of Herbivorous Dinosaurs Linked to Early Jurassic Global Warming Event."  The paper was written by a team led by Diego Pol, paleontologist at the Paleontological Museum Egidio Feruglio in Trelew, Argentina, and looked at a hitherto-unexplained overturning of Jurassic fauna that made way for the rise of the sauropods -- the largest land animals that have ever lived.

Skeleton of Apatosaurus [Image licensed under the Creative Commons Tadek Kurpaski from London, Poland, Louisae, CC BY 2.0]

The early Jurassic had a high dinosaur diversity, but then toward the middle of the period something happened, and a good many of the early Jurassic dinosaurs vanished.  They were replaced by behemoths like the familiar Brachiosaurus and the less-well-known but hilariously-named Supersaurus, which measured an almost unimaginable 33 meters from tip to tail.  (Even better, though, is the name Dreadnoughtus, which was shorter than Supersaurus -- "only" 26 or so meters long -- but is thought to be the heaviest land animal ever, on the order of thirty metric tonnes.)

So what caused the replacement of the earlier species by the giants?  Pol and his team found what they think is the smoking gun, a series of massive volcanic eruptions in southern Gondwanaland (what is now South America and Africa), which spiked the carbon dioxide content of the air, boosting the average temperature and dropping the pH of ocean water.  

The perturbation of the climate affected the plants first.  Earlier groups, like seed ferns and other smaller herbaceous plants, were replaced by conifers, which have tough, lignified stems, small needles or scales instead of leaves, and thick waxy cuticles to prevent water loss.  The problem is -- if you're an early Jurassic herbivorous dinosaur -- having evolved to eat seed ferns, you're not going to do so well trying to munch pine needles.

So as it always does, the change to the base of the food web percolated its way up to the top.  The early dinosaurs were replaced by big sauropods, who had grinding teeth (so tough plant material could be thoroughly pulverized before swallowing) and large stomachs (where food could sit and digest for a long time, extracting all the nutritive value possible).  The result was the arrival on the scene of monsters like Supersaurus and Dreadnoughtus and their cousins, which were the dominant land herbivores for a good hundred million years thereafter.

Sometimes new evidence results in our having to revise our previous models, overturning what we thought we knew.  Take, for example, the research that appeared this week in Royal Society Open Science that conclusively put to rest a commonly-held idea -- that by the time the Chicxulub Meteorite hit the Earth 66 million years ago, dinosaurs were already in a steep decline, so they would have disappeared anyhow, even without the massive impact that was the final death blow.

In "Dinosaur Diversification Rates Were Not in Decline Prior to the K-Pg Boundary," by a team led by Joseph Bonsor of the London Natural History Museum and the University of Bath, we find out that the dinosaurs were actually doing okay before the meteorite hit.  Far from being in decline, they would have been very likely to retain their position as the dominant animals on Earth well into the Cenozoic Era -- with effects on mammalian evolution that can only be imagined.

Bonsor, as befits a good scientist, is cautious about overconcluding.  "The main point of what we are saying is that we don't really have enough data to know either way what would have happened to the dinosaurs," Bonsor said in a press release from the Natural History Museum.  "Generally in the fossil record there is a bias towards a lack of data, and to interpret those gaps in the fossil record as an artificial decline in diversification rates isn't what we should be doing.  Instead we've shown that there is no strong evidence for them dying out, and that the only way to know for sure is to fill in the gaps in the fossil record."

But in the absence of positive evidence for a decline, we're thrown back to the null hypothesis; that they weren't in imminent danger of extinction.  So the whole idea of the dinosaurs as some kind of "failed experiment" in evolution is clearly wrong.  Not only did they kind of run things for a good two hundred million years -- which, by comparison, is something like a thousand times longer than we've been around -- they would probably have persisted for a good long while had a giant rock not interfered.

Me, I always want to know "what if?"  I think it comes from being a novelist; I'm always wanting to play around with reality and see what happens.  If the dinosaurs had stuck around for a long time rather than dying out 66 million years ago, it's hard to see how the rise of mammals -- and ultimately, us -- would have occurred.  Mammals had been around for a long while before the Chicxulub Impact, but they were mostly small, presumably kept that way both by the big carnivores and by competition with herbivores much larger than themselves.  So what would the Earth look like today?

Super-intelligent dinosaurs?  Maybe.  Evolution doesn't always point in the direction of "bigger and smarter;" it's the law of whatever works.  So as fun as it is to speculate, to be fair we have to side with Bonsor and say we just don't know.

Anyhow, that's our look back into the distant past for today.  Cool that we're still assembling new views of an old branch of biology.  Further reinforcing my opinion that if you're interested in science, you will never ever be bored.

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This week's Skeptophilia book-of-the-week is one that has raised a controversy in the scientific world: Ancient Bones: Unearthing the Astonishing New Story of How We Became Human, by Madeleine Böhme, Rüdiger Braun, and Florian Breier.

It tells the story of a stupendous discovery -- twelve-million-year-old hominin fossils, of a new species christened Danuvius guggenmosi.  The astonishing thing about these fossils is where they were found.  Not in Africa, where previous models had confined all early hominins, but in Germany.

The discovery of Danuvius complicated our own ancestry, and raised a deep and difficult-to-answer question; when and how did we become human?  It's clear that the answer isn't as simple as we thought when the first hominin fossils were uncovered in Olduvai Gorge, and it was believed that if you took all of our millennia of migrations all over the globe and ran them backwards, they all converged on the East African Rift Valley.  That neat solution has come into serious question, and the truth seems to be that like most evolutionary lineages, hominins included multiple branches that moved around, interbred for a while, then went their separate ways, either to thrive or to die out.  The real story is considerably more complicated and fascinating than we'd thought at first, and Danuvius has added another layer to that complexity, bringing up as many questions as it answers.

Ancient Bones is a fascinating read for anyone interested in anthropology, paleontology, or evolutionary biology.  It is sure to be the basis of scientific discussion for the foreseeable future, and to spur more searches for our relatives -- including in places where we didn't think they'd gone.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Viking dinosaurs

One of the main differences between skeptics and woo-woos is what we each think to be "sufficient evidence."

I ran into a great example of this yesterday, on S8intCom Blogger, which bills itself as "A Biblical View On Science."  (You are told on the homepage that "s8int" is pronounced "saint;" but by my linguistic analysis, "s8int" would be pronounced "satan-t," which is probably why they felt that the reader should be advised on how to pronounce it.)  In any case, most of the site is devoted to "proving" that the Great Flood of Noah happened, as per the Book of Genesis, that the Earth is 6,000 years old, that evolution is a big fat lie, and so on.  But one page struck me as especially interesting.  It was entitled "Ancient Viking Brachiosaurus," and makes the claim that the early inhabitants of Scandinavia depicted dinosaurs on their art -- because, well, real dinosaurs existed during the Viking age.

As evidence, they produce photographs of artifacts like this one, next to which they have helpfully superimposed a photograph of a brachiosaur skull and an artist's rendition of a brachiosaur, to make sure that you don't miss the similarity:

They also bring up the mention in Norse myth of giant serpents, like Ni∂hogg, the dragon who spent his time gnawing on the "World-Tree" Yggdrasil, and Jörmungandr, or "Midgard's serpent," the giant serpent that lay underwater, coiled around Midgard ("Middle-Earth," or the home of humans).  And this, we are told, is sufficient evidence to buy that dinosaurs were contemporaneous with humanity.

Okay, where do I start?

Let's begin with the artifact itself.  Even the S8intCom people admit that it hasn't been authenticated as being of genuine Viking make; in fact, they got the photograph of it from eBay, where it is being sold for $140 by some guy from Latvia.  Now, understand, it might be authentic; I'm not saying I have any reason to believe it isn't.  And questioning the artifact's provenance is only the beginning of the problems here.

A more serious problem is that dinosaurs of the genus Brachiosaurus are only known to come from the Morrison Formation, which is a Jurassic Age sedimentary rock formation... from western North America.  There were related forms, including Diplodocus, Apatosaurus, Camarosaurus, and others --  but the various long-necked sauropods seem to have been largely a group confined to what is now the western United States.  (There is some evidence from the fossil record that similar species may have occurred in North Africa, but that is uncertain.)  In any case, what's pretty clear is that at no time in the past did Brachiosaurus and his cousins stomp their way around Scandinavia.

Well, the Vikings were great travelers, right?  Maybe they saw live brachiosaurs on their travels, and were impressed (who wouldn't be?), and depicted them in their art.  Okay, but the problem is, they also depicted other things, like trolls, multi-headed giants, flying horses with eight legs, guys with magic hammers, hundred-foot-tall wolves, and boars made of gold that can run through the air.  And as far as I can see, S8intCom isn't claiming any of that is true.  They pick the one thing from Norse myth and art that supports their claim -- that dinosaurs coexisted with humans -- and conveniently ignore the rest.

We also have the additional problem that the two actual examples of dinosaur-like creatures mentioned in Norse myth -- Ni∂hogg and Jörmungandr -- aren't, really, all that dinosaur-like.  Ni∂hogg, in fact, lived underground, but liked visitors -- and he could talk, spending his time in riddles and abstruse arguments with any who would listen.  (Tolkien's talking dragons Smaug and Glaurung were almost certainly inspired by Ni∂hogg.)  As for Jörmungandr, he was thousands of miles long, and lived underwater, and was the offspring of the god Loki and the giantess Angrbo∂a.  Neither one of these sounds like any dinosaur I've ever heard of.

Last, if the dinosaurs were contemporaneous with the Vikings, why haven't we found any bones?  Or teeth?  Or anything?  There are animal remains that date from that age -- some that have been mummified, or partially fossilized (full fossilization usually takes longer than 1,000 years), and others that have had their bones or teeth fashioned into things like knife handles, jewelry, and the like.  Why no 1,000 year old dinosaur parts?

What I find most maddening about this whole thing is that the writers at S8intCom want to take a tiny part of scientific research -- the actual dinosaur bones themselves -- and an equally tiny part of antiquarian research into the art and myth of ancient Scandinavia, and effectively jettison the rest in favor of their own favorite Bronze Age mythological explanation of the world.  The rest of science -- that the Earth is a billion years old, that the dinosaurs (with the exception of the lineage that led to birds) died out during the Cretaceous Extinction 65 million years ago, that evolution is correct as per the evidence -- they ignore or argue away.  The depiction of things like flying horses and hundred-headed frost giants is considered the fanciful ravings of ignorant pagans, but a piece of dinosaur-like Norse jewelry is a valuable find that could overturn everything we understand about paleontology.  They're perfectly willing to take 1% of the evidence, and use it to support the ridiculous ideas they already had, and ignore the other 99% as misleading or downright wrong.

Now, don't get me wrong.  I'd just love it if the Norse myths were true.  They've always been my favorites, even if they take kind of a harsh view of the universe, what with the man-eating wolves and evil jotuns and fierce Valkyries, and the world getting destroyed at Ragnarokk, and all.  But at least they're better than the biblical myths, with an all-powerful, but petulant and capricious, god basically smiting the crap out of everyone for such egregious offenses as collecting firewood on the sabbath or eating shrimp or wearing clothes made of two different kinds of thread.  Given the choice, I'd take my chances with Odin and Loki and Thor.