Lost and found

I'm currently reading Michael Novacek's fascinating book Dinosaurs of the Flaming Cliffs, which is about the expeditions led by Novacek into the backcountry of the Mongolian Gobi Desert in search of late Cretaceous dinosaur fossils.

And they found 'em.  In abundance.  The remains that Novacek's team unearthed changed our understanding of the evolution of dinosaurs and early mammals in central Asia -- I've already lost count of the number of new species his group found, and I'm only about a third of the way through the book.

What struck me, though, is the combination of physical and personal hardship that the team members were willing to tolerate to achieve their goals.  The Gobi Desert is, even today, largely untraveled and unmapped; the nomadic groups that live in its arid wastes have to keep moving to survive in a climate that is broiling hot in the summer and viciously cold in the winter, has little in the way of drinkable fresh water, and is thin pasturage for domestic animals even at the best of times.  These scientists launched into the arid badlands in old, Soviet-era trucks that broke down every time someone sneezed hard, with carefully-rationed food, water, and gasoline, and exactly zero margin for error.

The fact that they not only survived, but achieved their scientific goals (and then some), is downright astonishing.  And every other page, I've shaken my head and thought, "I would never have the courage to do something like this.  Not in a million years."

Keep in mind, too, that this is coming from someone who did his share of backcountry camping, mostly in the Cascades and Olympics of Washington State.  Being a teacher has its perks -- June, July, and August being top of the list -- and when I was in my twenties I frequently disappeared into the fir-shrouded forests during the summer for weeks at a time.  So I'm no stranger to sleeping outdoors and hiking with a heavy pack.  (Or at least I was.  Now that I am Of A Certain Age, I'm afraid my appreciation of the creature comforts has done nothing but increase.)

But still: I would never have been brave enough to take off into the wilds of Mongolia the way Novacek et al. did (repeatedly).  Which probably would have scotched any intent I might have had to become a paleontologist.

On the other hand, sometimes -- admittedly, it's probably rare -- great paleontological discoveries can come from merely opening the right drawer in a museum.  The reason the topic comes up (besides my current reading-in-progress) is the chance find by paleontologist Georgios Georgalis of the Institute of Systematics and Evolution of Animals of the Polish Academy of Sciences in Krakow, who was doing some research in London's Natural History Museum and stumbled across the bones of a very unusual fossil snake that had been overlooked for forty years.

Dubbed Paradoxophidion richardoweni -- "Richard Owen's paradoxical snake" -- it lived in England during the Eocene Epoch, something like 37 million years ago.  At that point, England was a great deal warmer than it is now.  The world was just exiting the Paleocene-Eocene Thermal Maximum, at eight degrees Celsius higher than today one of the highest global average temperatures ever recorded.  The hot times favored diversification of ectothermic animals -- such as snakes -- in what are now regions with much cooler climates.

"It was my childhood dream to be able to visit the Natural History Museum, let alone do research there," said study lead author Georgalis.  "So, when I saw these very weird vertebrae in the collection and knew that they were something new, it was a fantastic feeling.  It's especially exciting to have described an early diverging caenophidian snake, as there's not that much evidence about how they emerged. Paradoxophidion brings us closer to understanding how this happened."

The snake species, Georgalis said, seems to be related to a group called acrochordids now found only in southeast Asia and Australia -- although more study is needed to be certain.  And it also brought up the tantalizing question of what else might be hiding in museum drawers and cabinets.

"I'm planning to study a variety of snake fossils in the collection, including those originally studied by Richard Owen" Georgalis said.  "These include the remains of the giant aquatic snake Palaeophis, which were first found in England in the nineteenth century.  There are also several bones with differing morphology that haven't been investigated before that I'm interested in looking at.  These might represent new taxa and offer additional clues about snake evolution."

So I guess you don't need to endure sandstorms and blistering heat and terrible food to make significant contributions to the field.

This also highlights the critical importance of museums in the entire scientific enterprise.  I found out yesterday the amazing news that one of our best local museums, the Paleontological Research Institution/Museum of the Earth, has received enough donations to remain open -- funding cuts were looking likely to shutter it permanently.  On the one hand, I'm thrilled that enough people were willing to donate to keep this wonderful place going (and if you're willing, I encourage you to go to their website and do so as well -- even if they met their goal, they can still put every penny to good use).  On the other, though, isn't it sad that we never seem to run out of money for stuff like funding war and paying kickbacks to corporate billionaires, but cutting-edge scientific establishments that are inspirations to thousands basically have to hold a bake sale to stay in business?

[Image licensed under the Creative Commons Matt Wedel, Yale brontosaurus, CC BY 4.0]

In any case, here's another puzzle piece adding to the picture of what the Earth was like tens of millions of years ago, that had been hidden away in a museum cabinet for four decades.  I find the whole thing endlessly fascinating, which probably explains why the topic of paleontology is such a frequent flier here at Skeptophilia. 

But as interested as I am, I still don't think I'd be brave enough to venture into the Gobi Desert to study it.

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Scattered to the winds

One of the more puzzling aspects of evolutionary theory is the phenomenon of peripheral isolates.

This term refers to widely-separated populations of seemingly closely-related organisms.  One of the first times I ran into this phenomenon came to my attention because of my obsession with birdwatching.  There's a tropical family of birds called trogons, forest-dwelling fruit-eaters that are prized by birdwatchers for their brilliant colors.  There are trogons in three places in the world... Central and South America (27 species), central Africa (3 species), and southern Asia (11 species).

These are very far apart.  But take a look at three representatives from each group -- it doesn't take an ornithologist to see that they've got to be closely related:

The Elegant Trogon (Trogon elegans) of Central America [Image licensed under the Creative Commons dominic sherony, Elegant Trogon, CC BY-SA 2.0]

The Narina Trogon (Apaloderma narina) of central Africa [Image licensed under the Creative Commons Derek Keats from Johannesburg, South Africa, Narina Trogon, Apaloderma narina MALE at Lekgalameetse Provincial Reserve, Limpopo, South Africa (14654439002), CC BY 2.0]

The Red-headed Trogon (Harpactes erythrocephalus) of southeast Asia [Image licensed under the Creative Commons JJ Harrison (jjharrison89@facebook.com), Harpactes erythrocephalus - Khao Yai, CC BY-SA 3.0]

I know, I've gone on and on in previous posts about how misleading morphology/appearance can be in determining relationships, but you have to admit these are some pretty convincing similarities.

The question, of course, is how did this happen?  Where did the group originate, and how did members end up so widely separated?  To add to the puzzle, the fossil record for the group indicates that in the Eocene Epoch, fifty-ish million years ago, there were trogons in Europe -- fossils have been found in Denmark and Germany -- and the earliest fossil trogons from South America come from the Pleistocene Epoch, only two million years ago.

So are these the remnants of what was a much larger and more widespread group, whose northern members perhaps succumbed due to one of the ice ages?  Did they start in one of their homelands and move from there?

And if that's true, why are there no examples of trogons from all the places in between?

Another example of this is the order of mammals we belong to (Primata).  Primates pretty clearly originated in Africa and spread from there; the earliest clear primates were in the Paleocene Epoch, on the order of sixty million years ago, but the ancestor of all primates was probably at least twenty million years before that, preceding the Cretaceous Extinction by fourteen million years.  From their start in east Africa they seem to have spread both east and west, reaching southeast Asia around fifty million years ago.  Some of the earliest members to split were the lorises and tarsiers, along with the lemurs of Madagascar.

But the next group to diverge -- and the reason the whole topic of peripheral isolates came up -- are the "New World monkeys," the "platyrhines" of Central and South America.  It looks like this split happened during the Oligocene Epoch, around thirty million years ago... but how?

At that point, Africa was separated from South America by nine hundred miles of ocean -- narrower than the Atlantic is today, but still a formidable barrier.  But a paper in Science describes recently-discovered evidence from Peru of some fossilized primate teeth from right around the time the New World/Old World monkey split happened.

What this discovery suggests is staggering; all of the New World monkeys, from the spider monkey to the black howler monkey to the Amazonian pygmy marmoset, are descended from a single group that survived a crossing of the Atlantic, probably on a vegetation raft torn loose in a storm, only a little over thirty million years ago.

"This is a completely unique discovery," said Erik Seiffert, the study's lead author and Professor of Clinical Integrative Anatomical Sciences at Keck School of Medicine of the University of Southern California, in an interview with Science Daily.  "We're suggesting that this group might have made it over to South America right around what we call the Eocene-Oligocene Boundary, a time period between two geological epochs, when the Antarctic ice sheet started to build up and the sea level fell.  That might have played a role in making it a bit easier for these primates to actually get across the Atlantic Ocean."

So here we have a possible explanation for one of the long-standing puzzles of evolutionary biology.  Note that these puzzles aren't a weakness of the theory; saying "we still have some things left to explain" isn't the same as saying "the theory can't explain this."  There will always be pieces to add and odd bits of data to account for, but I have one hundred percent confidence that the evolutionary model is up to the task.

Now, I wish it could just come with an explanation for the trogons, because for some reason that really bothers me.

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Footprints in the boneyard

The difficulty with paleontology is its inherent limitations.

There are, of course, things it's very good at.  In the hands of a skilled expert, fossils can tell you a great deal -- not only direct information about the parts that are preserved, but indirect information (from spaces, gaps, muscle attachment points, and so on) about the parts that were not.  I'm currently reading the wonderful book by Jack Horner and Edwin Dobb, Dinosaur Lives: Unearthing an Evolutionary Saga, and was astonished to find out that many paleontologists now believe that the quintessential Big Scary Dinosaur, Tyrannosaurus rex, was primarily a scavenger and not a hunter -- based upon the fact that the interior of the skull shows that its brain had an enormous olfactory lobe and a correspondingly small visual cortex, similar to hyenas and vultures.

Even so, there's a lot that fossils have a harder time telling us.  Other than a few fortuitous exceptionally-preserved feathers, we know next to nothing about colors and markings; art featuring prehistoric animals is almost entirely basing those features on guesswork using the patterns we see in modern animals.  In addition, how ancient organisms fit into the bigger ecological picture is like trying to figure out the pattern in a thousand-piece puzzle when you only have a handful of pieces. Given that a very small percentage of the biological remains left behind ever become fossils, chances are there are tens of thousands of prehistoric species we know absolutely nothing about because they left no traces behind after the last of their kind died.

Behavior, too, is often a puzzle.  It was Jack Horner (the same Jack Horner who co-wrote Dinosaur Lives) who made the discovery of the nesting and parental care behavior in the duckbilled dinosaur Maiasaura (the name means "good mother lizard"), based upon a group of fifteen fossilized juveniles and one adult that had been killed simultaneously in a volcanic ashfall.  But despite what Jurassic Park would have you believe, we really know very little about the behavior of prehistoric animals.  (Dilophosaurus, for example, almost certainly didn't have a retractable frill and poisonous spit.  Spit rarely fossilizes.)

The reason the topic comes up, actually, is because of a different volcanic eruption that left behind a treasure trove of fossils; a "supereruption" of the Yellowstone volcanic system twelve million years ago that smothered (and preserved) a huge herd of the prehistoric North American rhinoceros species Teleoceras.  The site -- in what is now northeastern Nebraska -- has been nicknamed "the rhino Pompeii."

"The eruption was so massive that ash would have fallen like snow 1,600 kilometers from the eruption site in Idaho," said Ashley Poust, a curator of vertebrate paleontology at the University of Nebraska State Museum, who gave a talk on the find last week at the annual meeting of the Society for Vertebrate Paleontology.  "This would have darkened the skies, buried plant life and water sources, and been a real hazard to anything with a delicate respiratory system."

A paleontologist working on unearthing Teleoceras fossils in the Ashfall Fossil Beds [Image credit: Ashley Poust]

What's most amazing about this find, though, is that the study also uncovered footprints in the ash -- the traces of two species of "bone-crushing dogs," Aelurodon taxoides and Epicyon saevus, which apparently somehow escaped being suffocated themselves and afterward made use of the huge amounts of free meat from the dead rhinos.  Aelurodon and Epicyon seem to have occupied the same niche as modern hyenas, but were a lot bigger; these prints were about eight centimeters long and seven centimeters wide.

Reconstruction of Epicyon [Image licensed under the Creative Commons Jarrod Amoore from Sydney, Australia, Epicyon, CC BY 2.0]

"There is some evidence that they may have scavenged among the animals who didn't survive, using the buried rhinos as a food cache," Poust said.  "But since we haven't found the bones of these meat eaters, we aren't sure yet whether this was enough to see them through to better times, or whether they eventually had to depart to seek their fortunes elsewhere in the massive disaster zone that covered much of North America."

It's also uncertain how they survived.  Volcanic ash is nasty stuff.  Not only does it clog airways if inhaled, it's made of sharp slivers of something very much like glass.  Even walking through a recent ashfall would raise enough dust to cause significant health risk, much less living through it while it was actively falling out of the sky.  Interesting that there haven't been any fossils of the dogs found at the site -- although research is ongoing, and it's anyone's guess about what's left there to discover.

So here's another case where we can made at least some tentative inferences about behavior from twelve million year old fossils.  Although the sad truth is that we still have access to information about only a tiny percent of the life that has ever existed on Earth, sometimes a chance discovery will give us a startling window into the past -- in this case about packs of scavengers that may have taken advantage of a catastrophic disaster.

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Life, not as we know it

I've written here before about unusual paleontological discoveries -- illustrations of the fact that Darwin's lovely phrase "many forms most beautiful and most wonderful" has applied throughout Earth's biological history.

We could also add the words "... and most weird."  Some of the fossils paleontologists have uncovered look like something from a fever dream.  A while back I wrote about the absolutely bizarre "Tully Monster" (Tullimonstrum spp.) that is so different from all other life forms studied that biologists can't even figure out whether it was a vertebrate or an invertebrate.  But Tully is far from the only creature that has defied classification.  Here are a few more examples of peculiar organisms whose placement on the Tree of Life is very much up for debate.

First, we have the strange Tribrachidium heraldicum, a creature of uncertain relationships to all species at the time or afterward.  It had threefold symmetry -- itself pretty odd -- and its species name heraldicum comes from the striking resemblance to the triskelion design on the coat of arms of the Isle of Man:

Tribrachidium fossil from near Arkhangelsk, Russia [Image licensed under the Creative Commons Aleksey Nagovitsyn (User:Alnagov), Tribrachidium, CC BY-SA 3.0]

Despite superficial similarities to modern cnidarians (such as jellyfish) or echinoderms (such as sea urchins and starfish), Tribrachidium seems to be neither.  It -- along with a great many of the Ediacaran assemblage, organisms that dominated the seas during the late Precambrian Era, between 635 and 538 million years ago -- is a mystery.

The Ediacaran is hardly the only time we have strange and unclassifiable life forms.  From much later, during the Carboniferous Period (on the order of three hundred million years ago), the Mazon Creek Formation in Illinois has brought to light some really peculiar fossils.  One of the most baffling is Etacystis communis, nicknamed the "H-animal":

Reconstruction of Etacystis [Image is in the Public Domain]

It's an invertebrate, but otherwise we're still at the "but what the hell is it?" stage with this one.  Best guess is it might be a distant relative of hemichordates ("acorn worms"), but that's speculative at best.

Next we have Nectocaris.  The name means "swimming shrimp," but a shrimp it definitely was not.  It next was thought to be some kind of primitive cephalopod, perhaps related to cuttlefish or squid, but that didn't hold water, either.  They had a long fin down each side that they probably used for propulsion, and a feeding tube shaped like a funnel (that you can see folded to the left in the photograph below):

Photograph of a Nectocaris fossil from the Burgess Shale Formation, British Columbia [Image is in the Public Domain]

All of the Nectocaris fossils known come from the early Cambrian.  It's possible that they were a cousin of modern chaetognaths ("arrow worms"), but once again, no one is really sure.

Another Cambrian animal that has so far defied classification is Allonnia, which was initially thought to be related to modern sponges, but their microstructure is so different they're now placed in their own order, Chancelloriidae.  You can see why the paleontologists were fooled for a while:

Reconstruction of Allonnia from fossils recovered from the Chengjiang Formation, Yunnan Province, China [Image licensed under the Creative Commons, Yun et al. 2024 f05 (preprint), CC BY 4.0]

At the moment, Allonnia and the other chancelloriids are thought to represent an independent branch of Kingdom Animalia that went extinct in the mid Cambrian Era and left no descendants -- or even near relatives.

Last, we have the bizarre Namacalathus hermanestes, which has been found in (very) late Precambrian shales in such widely-separated sites as Namibia, Canada, Paraguay, Oman, and Russia.  Check out the reconstruction of this beast:

[Image credit Zhuravlev, Wood, and Penny, Proceedings of the Royal Society B, November 2015]

It's been tentatively connected to lophophorates (which include the much more familiar brachiopods), but if so, it must be a distant relationship, because they look a great deal more like something H. P. Lovecraft might have dreamed up:

Unlike the, um, "Yuggothians," though, Namacalathus was quite real.  And, apparently, widespread.

The early Cambrian seas must have contained plenty of nightmare fuel.

And those are just five examples of organisms that would have certainly impelled Dr. McCoy to say, "It's life, Jim, but not as we know it."  Given how infrequently organisms fossilize -- the vast majority die, decay away, and leave no traces, and the vagaries of geological upheaval often destroy the fossil-bearing strata that did form -- you have to wonder what we're missing.  Chances are, for every one species we know about, there are hundreds more we don't.

What even more bizarre life forms might we see if we actually went back there into the far distant past?

I guess we'll have to wait until someone invents a time machine to find out.

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Old as the hills

In northwestern Australia, there's an administrative region called Pilbara.

Even though on a map, it looks kind of long and narrow, it's big.  The area of Pilbara is just shy of that of California and Nevada put together.  (I suspect that I'm like many non-Australians in consistently forgetting just how big Australia is.  It's the sixth largest country in the world, and is almost the same size as the continental United States.  Flying from Sydney to Perth is comparable to flying from Atlanta to Los Angeles.)

Pilbara is also extremely hot and dry, and very sparsely populated, with only a bit over sixty thousand residents total, most of whom live in the western third of the region.  The northeastern quadrant is part of the aptly-named Great Sandy Desert, one of the most inhospitable places on Earth.  There are only a few Indigenous tribes that somehow eke out a living there, most notably the Martu, but by and large it's uninhabited.

[Image licensed under the Creative Commons Brian Voon Yee Yap, aka Yewenyi, at en.wikipedia]

What brings up the topic, though, is that Pilbara is interesting for another reason than its hostile climate.

It is the home to some of the oldest rocks on Earth.

The Pilbara Craton -- a craton is a contiguous piece of continental crust -- is estimated to be around three and a half billion years old.  For reference, the Earth's crust only solidified 4.4 billion years ago.  Since that time, plate tectonics took over, and as I've described before, tectonic processes excel at recycling crust.  At collisional margins such as trenches and convergent zones, usually one piece slides under the other and is melted as it sinks.  Even in places where two thick, cold continental plates run into each other -- examples are the Alps and the Himalayas -- the rocks are deformed, buried, or eroded.

The result is we have very few really old rocks left.  The only ones even on the same time scale as Pilbara are the Barberton Greenstone Belt of South Africa and the Canadian Shield (and even the latter has been heavily metamorphosed since its formation).

This makes Pilbara a great place to research if you're interested in the conditions of the Precambrian Earth -- as long as you can tolerate lots of sand, temperatures that often exceed 36 C, and a fun kind of grass called Triodia that has leaf margins made of silica.

Better known as glass.

Frolicking in a field of Triodia is like running through a meadow made of Exacto knives.

Be that as it may, geologists and paleontologists have begun a thorough study of this fascinating if forbidding chunk of rock.  The most recent reconstructions suggest that both Pilbara and the aforementioned Barberton Greenstone were once part of an equatorial supercontinent called Vaalbara (which preceded the supercontinent most people think of -- Pangaea -- by a good three billion years).  And those might be the only chunks of that enormous piece of land left intact.

There are two other reasons Pilbara is remarkable.

It contains numerous fossilized stromatolites, which are layered sedimentary structures formed by cyanobacteria, thought to be the earliest photosynthetic life forms.  There are still stromatolites forming today -- probably not coincidentally, in shallow bays in Western Australia.

[Image licensed under the Creative Commons photographer Paul Harrison (Reading UK), March 2005, Stromatolites growing in Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia.]

As such, the Pilbara stromatolite fossils are the oldest certain traces of life on Earth, dating to 3.48 billion years ago.

The other reason is that it's also home to a massive impact crater dating to 3.47 billion years ago.  Shortly after those earliest, tentative life forms were living and thriving in the warm shallow ocean waters, a huge meteorite struck near what is now the town of Marble Bar, forming a crater and shatter cone between 16 and 45 kilometers in diameter (because of erosion, it's hard even for the geologists to determine where its edges lie).  The resulting Miralga Impact Structure blew tremendous amounts of molten debris up into the air, and some of it landed on that chunk of Vaalbara that would eventually end up in South Africa -- only to be recovered by geologists almost three and a half billion years later.

So there's a place in Australia that gives new meaning to the phrase "old as the hills."  Given its remoteness and inhospitable climate, I'm unlikely ever to visit there, but there's something appealing about the idea.  Walking on rock that is an intact remnant of a continent from over three billion years ago is kind of awe-inspiring.  Even if all the other rock is still here somewhere -- melted and reformed and eroded multiple times -- the idea that this chunk of the Earth has somehow lasted that long more or less intact is mighty impressive.

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Mental models and lying stones

Richard Feynman famously said, "The first principle is that you must not fool yourself -- and you are the easiest person to fool."

This insightful statement isn't meant to impugn anyone's honesty or intelligence, but to highlight that everyone -- and I'm sure Feynman was very much including himself in this assessment -- has biases that prevent them from seeing clearly.  We've already got a model, an internal framework by which we interpret what we experience, and that inevitably constrains our understanding.

As science historian James Burke points out, in his brilliant analysis of the scientific endeavor The Day the Universe Changed, it's a trap that's impossible to get out of.  You have to have some mental model for how you think the world works, or all the sensory input you receive would simply be chaos.  "Without a structure, a theory for what's there," Burke says, "you don't see anything."

And once you've settled on a model, it's nearly impossible to compromise with.  You're automatically going to take some things as givens and ignore others as irrelevant, dismiss some pieces of evidence out of hand and accept others without question.  We're always taking what we experience and comparing it to our own mental frameworks, deciding what is important and what isn't.  When my wife finished her most recent art piece -- a stunning image of a raven's face, set against a crimson background -- and I was on social media later that day and saw another piece of art someone had posted with a raven against red -- I shrugged and laughed and said, "Weird coincidence."

Quoth the Raven, pen/ink/watercolor by Carol Bloomgarden (2025) [Image used with permission]

But that's only because I had already decided that odd synchronicities don't mean anything.  If I had a mental model that considered such chance occurrences as spiritually significant omens, I would have interpreted that very, very differently.

Our mental frameworks are essential, but they can lead us astray as often as they land us on the right answer.  Consider, for example, the strange, sad case of Johann Beringer and the "lying stones."

Johann Bartholomeus Adam Beringer was a professor of medicine at the University of Würzburg in the early eighteenth century.  His training was in anatomy and physiology, but he had a deep interest in paleontology, and had a large collection of fossils he'd found during hikes in his native Germany.  He was also a devout Lutheran and a biblical literalist, so he interpreted all the fossil evidence as consistent with biblical events like the six-day creation, the Noachian flood, and so on.

Unfortunately, he also had a reputation for being arrogant, humorless, and difficult to get along with.  This made him several enemies, including two of his coworkers -- Ignace Roderique, a professor of geography and algebra, and Johann Georg von Eckhart, the university librarian.  So Roderique and von Eckhart hatched a plan to knock Beringer down a peg or two.

They found out where he was planning on doing his next fossil hunt, and planted some fake fossils along the way.

These "lying stones" are crudely carved from limestone.  On some of them, you can still see the chisel marks.

More outlandish still, Roderique and von Eckhart carved the word "God" in Hebrew on the backs of some of them.  Making it look like the artisan had signed His name, so to speak.

One colleague -- who was not in on the prank -- looked at the stones, and said to Beringer, "Um... are you sure?  Those look like chisel marks."  Beringer dismissed his objections, and in fact, turned them into evidence for his explanation.  Beringer wrote, "...the figures... are so exactly fitted to the dimensions of the stones, that one would swear that they are the work of a very meticulous sculptor...[and they] seem to bear unmistakable indications of the sculptor's knife."

They were so perfect, Beringer said, that they could only be the work of God.

So as astonishing as it may seem, Beringer fell for the ruse hook, line, and sinker.  Roderique and von Eckhart, buoyed up by their success, repeated their prank multiple times.  Finally Beringer had enough "fossils" that in 1726, he published a scholarly work called Lithographiae Wirceburgensis (The Writing-Stones of Würzburg).  But shortly after the book's publication -- it's unclear how -- Beringer realized he'd been taken for a ride.

He sued Roderique and von Eckhart for defamation -- and won.  Roderique and von Eckhart were both summarily fired, but it was too late; Beringer was a laughingstock in the scientific community.  He tried to recover all of the copies of his book and destroy them, but finally gave up.  His reputation was reduced to rubble, and he died twelve years later in total obscurity.

It's easy to laugh at Beringer's credulity, but the only reason you're laughing is because if you found such a "fossil," your mental model would immediately make you doubt its veracity.  In his framework -- which included a six-thousand-year-old Earth, a biblical flood, and a God who was perfectly capable of signing his own handiwork -- he didn't even stop to consider it.

The history of science is laden with missteps caused by biased mental models.  In 1790, a report of a fireball over France that strewed meteorites over a large region prompted a scientific paper -- that laughingly dismissed the claim as "impossible."  Pierre Bertholon, editor of the Journal des Sciences Utiles, wrote, "How sad, is it not, to see a whole municipality attempt to certify the truth of folk tales… the philosophical reader will draw his own conclusions regarding this document, which attests to an apparently false fact, a physically impossible phenomenon."  DNA was dismissed as the genetic code for decades, because of the argument that DNA's alphabet only contains four "letters," so the much richer twenty-letter alphabet of proteins (the amino acids) must be the language of the genes.  Even in the twentieth century, geologists didn't bother looking for evidence for continental drift until the 1950s, long after there'd been significant clues that the continents had, in fact, moved, largely because they couldn't imagine a mechanism that could be responsible.

Our mental models work on every level -- all the way down to telling us what questions are worth investigating.

So poor Johann Beringer.  Not to excuse him for being an arrogant prick, but he didn't deserve to be the target of a mean-spirited practical joke, nor does he deserve our derision now.  He was merely operating within his own framework of understanding, same as you and I do.

I wonder what we're missing, simply because we've decided it's irrelevant -- and what we've accepted as axiomatic, and therefore beyond questioning?

Maybe we're not so very far ahead of Beringer ourselves.

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A light on bias

A woman walks into the kitchen to find her husband on all fours, crawling around peering at the floor.

"What are you doing?" she asks.

"Looking for my contact lens."

"Oh, I'll help."  So the woman gets down on the floor, too, and they spend the next fifteen minutes fruitlessly searching for the missing lens.  Finally, she says, "I just don't see it.  Are you sure you dropped it in here?"

The husband responds, "Oh, no, I dropped it in the living room."

"Then why the hell are you looking for it in the kitchen?" she yells at him.

"Because the lighting is better in here."

While this is an old and much-retold joke, there's an object lesson here for scientists -- which was highlighted by a paper this week out of George Washington University that appeared in Nature Ecology & Evolution.  In it, paleobiologists Andrew Barr and Bernard Wood considered a systematic sampling bias in our study of fossils of ancestral hominid species -- and by extension, every other group of fossils out there.

A large share of what we know of our own early family tree comes from just three sites in Africa, most notably the East African Rift Valley and adjacent regions in Ethiopia, Kenya, and Tanzania.  Clearly that's not the only place early hominids lived; it's just the place that (1) has late Cenozoic-age fossil-bearing strata exposed near the surface, and (2) isn't underneath a city or airport or swamp or rain forest or something.  In fact, the Rift Valley makes up only one percent of Africa's surface area, so searching only there is significantly biasing what we might find.

[Image licensed under the Creative Commons Michal Huniewicz, Great Rift Valley - panoramio, CC BY 3.0]

"Because the evidence of early human evolution comes from a small range of sites, it's important to acknowledge that we don't have a complete picture of what happened across the entire continent," said study co-author Andrew Barr.  "If we can point to the ways in which the fossil record is systematically biased and not a perfect representation of everything, then we can adjust our interpretations by taking this into account."

You can only base your understanding on what evidence you actually have in your hands, of course; besides the areas that might bear fossils but are inaccessible to study for one reason or another, there are parts of Africa where the strata are from a different geological era, or simply don't contain fossils at all (for example, igneous rock).  But you still need to maintain an awareness that what you're seeing is an incomplete picture.

"We must avoid falling into the trap of coming up with what looks like a comprehensive reconstruction of the human story, when we know we don't have all of the relevant evidence," said study co-author Bernard Wood.  "Imagine trying to capture the social and economic complexity of Washington D.C. if you only had access to information from one neighborhood.  It helps if you can get a sense of how much information is missing."

Now, don't misunderstand me (or them); no one is saying what we have to date is likely to be all wrong.  I absolutely hate when some new fossil is discovered, and the headlines say, "New Find Rewrites Everything We Knew" or "The Textbooks Are Wrong Again" or, worst of all, "Scientists Are Forced Back To The Drawing Board."  For one thing, our models are now solid enough that it's unlikely that anything will force a complete undoing of the known science.  I suppose something like that could occur in newer fields like cosmology and quantum physics, but even there we have tons of evidence and excellent predictive models -- so while there might well be additions or revisions, a complete overturning is almost certainly not gonna happen.  

Second, as astrophysicist Neil deGrasse Tyson put it, "As scientists, we're always at the drawing board.  If you're not at the drawing board, you're not doing science."  We are always exploring what he calls "the perimeter of our ignorance," testing and probing into the realms we have yet to explain fully.  What Barr and Wood are doing for the field of human paleobiology is to define that perimeter more clearly -- to identify where our inevitable sampling biases are, so that we can determine what direction to look next.  Not, like our hapless contact-lens-searchers, to continue to look in the same place just because the lighting happens to be better there.

Biases are unavoidable; everyone's got 'em.  The important thing is to be aware of them; they can't bite you on the ass if you keep your eye on them.  In science -- well, in everything, really -- it's good to remember the iconic line from physicist Richard Feynman: "The first principle is that you must not fool yourself; and you are the easiest person to fool."

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The migrants

Most people know of at least two reasons that organisms can evolve.  The first, of course, is natural selection; members of the same species with inheritable differences can have different survival rates or reproductive rates, leading to overall shifts in the genetic makeup of the population.  The second is catastrophe; a major external event, such as the eruption of the Siberian Traps or the collision of the Chicxulub Meteorite, can completely destabilize what had been a thriving ecosystem, and cause the selective pressures to go off in a completely different direction.  (The two I mentioned were the dominant factors in the Permian-Triassic and Cretaceous-Tertiary extinctions, respectively.)

Less well-known is the role that plate tectonics can play.  When two land masses split apart, the organisms then go their separate ways evolutionarily, especially once the two pieces drift far enough away from each other to experience significantly different climates.  This is what happened to Australia, which most recently was connected to Antarctica; once they diverged, Australia moved northward and Antarctica southward, resulting in just about everything in Antarctica becoming extinct as the temperatures dropped, and leaving Australia with its unique assemblage of species.

The opposite can happen when two continents run into each other.  This occurred when India separated from Africa and collided with Asia, about fifty million years ago, carrying with it species from the southern supercontinent (Gondwana) and introducing them to the northern one (Laurasia).  But an even more striking example occurred when North and South America got close enough that a bit of the seafloor was pushed above water, creating the Isthmus of Panama.

When this happened, on the order of three million years ago, it opened up an easy avenue of two-way migration between the two continents.  This reconnected land masses that had been separated since the breakup of Pangaea in the early Triassic Period, on the order of two hundred million years ago.  That's a long time for species assemblages to evolve in their own directions, and the result was two entirely different floras and faunas.  Those began to move back and forth across the gap as soon as the isthmus formed.

What is curious -- and still largely unexplained -- is why the survival rates of the northward and southward migrants were so drastically different.  Species went both directions; that much is clear from the fossil record.  But just looking at mammals, South America gained (and still has) various species of cats, wolves, foxes, peccaries, deer, skunks, bears, and mice that it gained from North America, to name only a few of the groups that moved in and thrived.  But going the other direction?

There were only three survivors.  The opossum, the armadillo, and the porcupine are the only mammalian South American imports we still have around today.  Others that attempted the northward trek, including ground sloths, glyptodonts, "terror birds," sparassodonts, notungulates, and litopterns, struggled along for a while but eventually became extinct.

[Image is in the Public Domain]

The surmise is that moving from wet forests where it's warm year-round into cooler, drier temperate deciduous forests or grasslands is harder than the reverse, just from the perspective of resources.  Whatever the reason, though, it altered the ecosystems of South America forever, as the North American species proved to be better competitors (and predators), driving entire families of South American mammals extinct.  Some groups continued to thrive and diversify, of course.  Hummingbirds come to mind; they're a distinctly South American group. increasing in diversity as you head south.  Where I live, there's a grand total of one species of hummingbird (the Ruby-throated Hummingbird).

The little country of Ecuador has 132.

The reason all this comes up is the discovery of the complete skeleton of an extinct species of porcupine in Florida, dating to 2.5 million years ago -- and therefore, one of those early migrants northward from its ancestral homeland.  It's related to the modern North American species, but definitely not the same; the extinct species, for example, had a prehensile tail, similar to modern South American species (and which our North American porcupines lack).  It's still unknown, however, if the Florida species is ancestral to our current North American porcupines, or if they're cousins; further study of the skeleton may help to resolve that question.

It's fascinating, though, to see the fingerprints of this mass migration that was to change so radically two different continents.  The process of plate movement continues; Australia will eventually collide with Asia, for example, with similar results, mixing together two sets of species that have been isolated for millions of years.  Change is inevitable in the natural world; it can happen quickly or slowly, and sometimes occurs in ways we're just beginning to understand.

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Lords of the air

Ever since I was a kid, my favorite group of dinosaurs has been the pterosaurs.

These are one of the six groups of animals that independently evolved flight, or at least significant capacity for gliding (the others are insects, birds, bats, flying squirrels, sugar gliders, and colugos).  They had incredible diversity at their height, during the Jurassic and Cretaceous Periods, from the pint-sized Sordes pilosus (with a sixty-centimeter wingspan) to the almost unimaginably huge Quetzalcoatlus northropi (with a ten-meter wingspan, as big as a light plane).

Most of them were probably clumsy on the ground -- it's hard to imagine how Quetzalcoatlus got off the ground -- but in the air, they were nimble, maneuverable, and fast.  The smaller ones were probably insect-eaters; the larger ones likely fed on fish, although a terrestrial diet of small reptiles and mammals is also possible. 

What brings all this up is the discovery of a new species of pterosaur, one of dozens that have been identified from the Jehol Biota, a stupendous fossil deposit in northeastern China near Huludao.  This fossil bed has produced not only pterosaurs but incredibly well-preserved species of prehistoric birds and other vertebrates -- it's like a tapestry of late Cretaceous animal life.

"Pterosaurs comprise an important and enigmatic group of Mesozoic flying reptiles that first evolved active flight among vertebrates, and have filled all aerial environmental niches for almost 160 million years," said Xiaolin Wang, of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences, who co-authored the paper describing the discovery.  "Despite being a totally extinct group, they have achieved a wide diversity of forms in a window of time spanning from the Late Triassic to the end of the Cretaceous period.  Notwithstanding being found on every continent, China stands out by furnishing several new specimens that revealed not only different species, but also entire new clades."

This includes the newly-discovered Meilifeilong youhao, belonging to the family Chaoyangopteridae, which is represented at the site by two other species that have been found nowhere else.

Meilifeilong looked like something out of a nightmare, if the artist's reconstruction is accurate (and probably even if it isn't):

[Image courtesy of artist Maurilio Oliveira]

The name means "beautiful flying dragon," which I doubt is what I'd say if I saw one, but what I'd say is borderline unprintable so we'll leave it at that.

It's astonishing to think of how long these creatures ruled the skies -- from the late Triassic until the very end of the Cretaceous, a time span of around 160 million years.  Had change not come in the form of the Chicxulub Meteorite collision, they might well still be here, soaring on thermals above our forests and lakes and oceans, the undisputed lords of the air.  And even if we now know them only from fossils, they still can't help but impress.

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