The hills are shadows

One of the reasons I became a speculative fiction novelist is because I love to think about how the world would be if the rules were different.  What if we could pick up from inanimate objects the emotional impressions of the last person who held them?  What if time travel into the past were possible?  What if the force of someone's desires could alter reality, without their being aware of it?

The difficulty is that this dreaminess about tampering with the laws of the universe runs headlong into my desire to understand what the actual rules are, and which ultimately led me to dedicate my life to science.  After an unfortunate time in my teenage years when I worked really, really hard to convince myself that all the weird paranormal shit I'd immersed myself in was the truth, I was forced by the modicum of intellectual honesty I had back then to admit that the evidence for all of it was nil, and to give the whole thing up as a bad job.

So I ended up teaching science and critical thinking, and simultaneously writing paranormal fiction.  Seemed like a good compromise.

But this push to explore the fringes still shows up.  I'm most attracted to the areas of science that are strange and counterintuitive.  Regular readers of Skeptophilia will attest to this, given my near obsession with things like quantum physics and the behavior of black holes.  And there's one other realm of science that allows me to do what journalist Kathryn Schulz calls "seeing the world as it isn't" -- and that's paleontology.

Because after all, things in the distant past were very, very different than they are now.  We're so used to looking around us and seeing The World As It Is that we don't often consider that this brief point in time is part of a continuum of geological and biological change, and is framed on both sides -- past and future -- by worlds that were and will be wildly different from the one we live in.

As an example, consider a paper in the journal ZooKeys, which is about the fauna of the Sahara.  Immediately I said that name, I'm guessing you pictured sand dunes, perfectly clear blue skies, no plant life (maybe a palm tree or two, if there was an oasis in your imagination), and perhaps a camel or a white-robed Bedouin.

Turn the chronometer back a hundred million years, though, and you wouldn't even know it was the same place.

At that point, the Sahara was a tropical forest, with a huge bay of the Tethys Ocean (the remnant of which we now call the Indian Ocean) right in the middle.  The Atlantic Ocean had only recently opened up, and western Africa was separated from South America by a narrow strait.  What is now an unbroken swath of desert was a large island in the west, a smaller island in the middle of the central bay, and a big chunk of land to the east that is now the remainder of the continent of Africa.

A map of the continents during the late Cretaceous Period [Image licensed under the Creative Commons Mannion, P. D. (2013). "The latitudinal biodiversity gradient through deep time".  Trends in Ecology and Evolution 29 (1). DOI:10.1016/j.tree.2013.09.012., LateCretaceousMap, CC BY-SA 3.0]

But that just scratches the surface.  The paper I referenced above, "Geology and Paleontology of the Upper Cretaceous Kem Kem Group of Eastern Morocco," by a team led by Nizar Ibrahim of the University of Detroit, describes the fossil finds in the Kem Kem Group, a dazzlingly rich fossil bed that is only now beginning to be investigated thoroughly.

What this fossil bed shows us is a world that's not only drastically different from how we picture the Sahara today, it's drastically different from anything currently on Earth.  "This was arguably the most dangerous place in the history of planet Earth," Ibrahim said in an interview in Science Daily, "a place where a human time-traveller would not last very long."

Such a time-traveller, in their short remaining life expectancy, would meet up with such beasts as Carcharodontosaurus -- the name means "jagged-toothed lizard" -- which averaged eight meters from tip to tail, just shy of the length of an average school bus.  Its signature teeth were twenty centimeters long and serrated like steak knives.  There were twenty-meter-long crocodilians such as Aegisuchus, which were big enough to turn your average modern saltwater crocodile into saltwater taffy.  There was the fifteen-meter-long, twenty-ton Spinosaurus, another carnivore.  The skies were no safer -- there was a variety of pterodactyloids, including the flying hunter Apatorhamphus, which had a long, needle-toothed snout and a wingspan of five meters.

And that's just a sampler.

"Many of the predators were relying on an abundant supply of fish," said study co-author Professor David Martill from the University of Portsmouth.  "This place was filled with absolutely enormous fish, including giant coelacanths and lungfish.  The coelacanth, for example, is probably four or even five times larger than today's coelacanth [which averages two meters in length].  There is an enormous freshwater saw shark called Onchopristis with the most fearsome of rostral teeth, they are like barbed daggers, but beautifully shiny."

So if you went for a swim, at least you'd have something pretty to look at while you were being messily devoured.

But the vagaries of plate tectonics and climate eventually widened the Atlantic and closed off the bay in the mid-Sahara, and the place started to dry out.  It was green for a lot longer than you'd think, however.  There's evidence that as little as seven thousand years ago, the Sahara got a great deal more rain and was much more verdant than it is today, but a shift in the path of the African monsoon turned off the tap and converted the whole area into a vast, mostly-uninhabitable desert.

I'd like to close with the beautiful and poignant words Alfred, Lord Tennyson wrote in his poem "In Memoriam."  I've quoted them here before, but they are so apposite there's really no fitter way to end.  Read this, and think about the Sahara -- and what your own homeland might look like in a hundred million years' time.

There rolls the deep where grew the tree.
O Earth, what changes hast thou seen?
There where the long road roars has been
The stillness of the central sea.
The hills are shadows, and they flow
From form to form, and nothing stands,
They melt like mists, the solid lands,
Like clouds, they shape themselves, and go.

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Danger down under

Around my neck of the woods we like to complain a lot in spring about the blackflies and mosquitoes, but by and large, compared to most places we have pretty placid wildlife.  Me, I'm not so fond of the yellowjackets that nest underground and pack a nasty sting, but even they're not that big a deal compared to what some people have to contend with.  And even Australia -- a place notorious for its dangers -- should give thanks for the fact that they're not as bad as they used to be, at least according to a paper in Nature Communications that falls under the "You think things are scary now?" department.

Of course, it's not like even the modern Australian wildlife is anything to trifle with.  The country is where you can find some of the world's most dangerous snakes, including the taipan, the brown snake, and the tiger snake.  The north coast is home to the enormous and aggressive saltwater crocodile, while the south coast has a sizable population of great white sharks.  The eastern coast, not to be outdone, is where you can run into the harmless-looking box jellyfish, which is in contention for winner of the most-potent venom contest; it injects its victim with a substance that has an LD-50 of 0.04 milligrams per kilogram of body weight, and can kill in under five minutes if an antidote isn't administered.  Even the plants bear watching.  The north coast has the beach spinifex grass, which reinforces the pointed tips of its leaves with silica drawn from the soil, essentially turning the plant into a cluster of tiny glass shards.  Worst of all is the gympie-gympie, which is like the humongous nettle from hell, inflicting an excruciating sting that can last for years.

(The Wikipedia article I linked says that the fruit of the gympie-gympie is "edible if the stinging hairs are removed first."  To which I respond, "Do I look like a fucking lunatic to you?"  I'll stick with fruit that's not attempting to murder me, thanks.)

But the paper "Extinction of Eastern Sahul Megafauna Coincides with Sustained Environmental Deterioration," by a team led by Scott Hocknull of the University of Melbourne, gives you a good feeling for how much worse it could be.  It describes a treasure-trove of fossils from Walker Creek in northeastern Australia that had the remains of hitherto-unknown species of fauna, including:

• a thus-far unclassified kangaroo that was four meters tall and weighed just shy of three hundred kilograms
• a new species of the genus Diprotodon, which was basically a wombat on steroids -- it's estimated to have been two meters tall at the shoulder and had a mass of 2,500 kilograms
• a new species of the horrific carnivorous marsupial Thylacoleo, which was slightly smaller than your average African lion, but is estimated to have had the most powerful bite of any known mammal, living or extinct
• a six-meter-long goanna and two never-before-seen species of monitor lizards
• a land-dwelling crocodile, because apparently the water-dwelling ones weren't bad enough

Artist's reconstruction of Thylacoleo carnifex [Image licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com), Thylacoleo BW, CC BY 3.0]

The kicker is that these things were around after the colonization of Australia by humans, and in fact, by some estimates there was a fifteen thousand year overlap where the ancestors of today's Native Australians had to contend with a nightmarish megafauna.  Me, I wonder why they stuck around, you know?  If I was one of them, and landed in my boat on the shores of Australia, and saw land crocodiles and six-meter-long lizards and a lion-sized Tasmanian devil, I would have used the words of the inimitable Eric Cartman: "Screw you guys, I'm goin' home."

Of course, home was Papua-New Guinea, which honestly wasn't all that much better.

It's an interesting question as to what finally did in these formidable critters.  Hocknull et al. write the following, in an article in The Conversation:

Why did these megafauna become extinct?  It has been argued that the extinctions were due to over-hunting by humans, and occurred shortly after people arrived in Australia.

However, this theory is not supported by our finding that a diverse collection of these ancient giants still survived 40,000 years ago, after humans had spread around the continent.

The extinctions of these tropical megafauna occurred sometime after our youngest fossil site formed, around 40,000 years ago.  The timeframe of their disappearance coincided with sustained regional changes in available water and vegetation, as well as increased fire frequency.  This combination of factors may have proven fatal to the giant land and aquatic species.

As magnificent as these creatures undoubtedly were, it's probably better that they're gone.  I've heard Australia is a pretty cool place, even considering its dangerous flora and fauna, but if the animals of Walker Creek were still around, it'd be hard to understand how anyone could manage to live there.  Just taking a short walk to the grocery store would be risking getting dismembered by enormous carnivorous marsupials.

Makes today's snakes and crocodiles and whatnot seem tame by comparison, doesn't it?

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Reptilian splits

One of my favorite lectures in my AP Biology class was about how there's no such thing as a reptile.

If you took your last biology class before about 1995, you probably learned about Class Reptilia, containing turtles, lizards, snakes, crocodiles, alligators, and a few other assorted groups.  The class was defined by having dry, scaly skin, internal fertilization, "amniote" eggs with shells, and hearts that had incomplete septa (the wall down the center that separates the oxygenated left side from the deoxygenated right side).

Well, the last one wasn't 100% true, and that should have been a clue to what was going on.  Crocodiles and alligators have four-chambered hearts, and are also partial endotherms -- they show some capacity for internally regulating their own body temperatures, just as birds and mammals do.

It was genetic testing that finally settled who was related to whom, and that was when a lot of us got a shock (not so much the evolutionary biologists, who kind of expected this was how it was gonna work out).  The word "reptile" has no real taxonomic significance, because it lumps together groups that really aren't very closely related, and excludes others that are closer. Here's how this branch of Kingdom Animalia evolved:

As you can see from the diagram, the problem was birds.  Crocodiles are more closely related to birds than they are to lizards (despite superficial appearance); and if you throw dinosaurs into the mix, it becomes even clearer, because birds are dinosaurs.

Think about that the next time you feed the chickadees.

So if you throw all the reptiles together, by the rules of cladistic taxonomy, you'd have to include birds, and nobody much wanted to call birds reptiles.  So the entire Class Reptilia was broken up, now as three different classes: Lepidosauria (lizards, snakes, and the oddball tuatara of New Zealand), Testudines (turtles), and Crocodilia (obviously crocodiles et al.).  Birds have their own class (Aves).

But what this brings up is how such different-looking animals as turtles and snakes evolved from a common ancestor.  The differences between the different groups of reptiles is pretty dramatic.  The explanation has usually been that it was adaptive radiation, a phenomenon that deserves some explanation.

Adaptive radiation is when a group undergoes rapid diversification to fill many available niches.  The classic example is Darwin's finches, a group of birds on the Galapagos Islands, which descend from a common ancestral group that split up to occupy different niches because of bill size and strength (which determines what they can eat).  That's a pretty drastic oversimplification, but it captures the essence: many available niches, and a population with sufficient genetic diversity to split up and specialize into those niches.

Because of the "many available niches" part, adaptive radiation is most common under two scenarios: a population colonizing a previously-uninhabited territory (as with Darwin's finches), and remnant populations left after a major extinction.  This was what was thought to have powered the split-up of the reptiles -- the "Great Dying," the Permian-Triassic extinction of 252 million years ago that by some estimates wiped out 95% of life on Earth.

Nota bene: there is fairly good evidence that the trigger for the Permian-Triassic extinction was hypercapnia -- a sudden increase in atmospheric carbon dioxide.  This led to drastic warming of the atmosphere and ocean acidification. The cause -- according to a paper in the journal Geology -- was massive burning of coal.  Sound familiar?  In this case the cause was natural; it's thought to have been triggered by extensive volcanism ripping through huge deposits of coal and carbonate minerals formed during the Carboniferous Period.  But the end result was the same as what we're doing now by runaway use of fossil fuels.  I'd like to think this would be a cautionary note, but the world's leaders seem to specialize in ignoring science unless it can directly make them money and/or keep them in power, so I'm not holding my breath.

But back to the reptiles. The study that triggered this post, which appeared in Nature Communications, points out the flaw in the argument that the adaptive radiation of reptiles was due to the Permian-Triassic extinction.  According to recent analysis, the split up was already well underway before the extinction started.  And the extinction itself was sudden, at least in geological terms; from start to catastrophic finish, the whole event took about a hundred thousand years.  In geological strata, this length of time is a very, very narrow band.

Plus, the different groups of reptiles individually show drastically different rates of specialization.  "Our findings suggest that the origin of the major reptile groups, both living and extinct, was marked by very fast rates of anatomical change, but that high rates of evolution do not necessarily align with taxonomic diversification," said study lead author Tiago Simões of Harvard University, in an interview in Phys.Org.  "Our results also show that the origin of snakes is characterized by the fastest rates of anatomical change in the history of reptile evolution -- but that this does not coincide with increases in taxonomic diversity [as predicted by adaptive radiations] or high rates of molecular evolution."

The end result of the study is that the cause of the adaptive radiation is unknown.  It probably was pushed along by the mass extinction -- the species that survived the hypercapnia and the resulting environmental devastation were set up to have a whole empty world to colonize.  But what was driving the split-up of the group prior to the extinction itself?

Unknown, but the current study shows that clearly the adaptive radiation had already started.

I love puzzles like this.  In science, there are almost always more questions than answers, and every answer brings up new questions.  But another feature of science is the conviction that there is an answer even if we don't currently know what it is. And chances are, further study will elucidate what exactly was going on -- and what led to the fragmentation of a group that now, over 250 million years later, comprises some of the best-known and most familiar critters who have ever walked (or slithered, or flown across) the Earth.

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The road not taken

One of the most intriguing sets of life forms I've ever heard of is the Ediacaran Assemblage.

It dates from the late Precambrian Era -- something on the order of 570 million years ago -- and is named after the Ediacara Hills of Australia, where rocks of that age are exposed at the surface.  They're sometimes conflated with the Cambrian Explosion fauna like the ones in the famous Burgess Shale, but any connection between the two is tenuous at best.  Not only are they separated by almost seventy million years, the Burgess Shale animals are (mostly) from phyla we know about.  A few -- like the bizarre and aptly-named Hallucigenia -- have more obscure relationships to modern life, but most of the fossils we find there are identifiably proto-arthropods or proto-annelids or proto-whatnot.  So while the Cambrian Explosion fauna is fascinating in its own right, by and large it's still fairly familiar ground.

Not so the Ediacaran Assemblage.

These things are downright mysterious.  Take, for example, the group called rangeomorphs.

They may have been animals, although they were sessile (fixed to the seafloor) via stalks, and had weird frond-like structures of uncertain purpose (but which may have been a mechanism either for oxygen extraction or for filter feeding).  So if you were to look at a living one, your initial impression might well be that it was some odd sort of seaweed, and not an animal at all.

A 550-million-year-old fossil of the rangeomorph Charnia masoni, from the Mistaken Point Formation in Newfoundland [Image licensed under the Creative Commons Smith609 at English Wikipedia, Charnia, CC BY 2.5]

Not only are they bizarre-looking, many seem to have no living descendants, including Obamus coronatus (which looks like a French cruller) and the hubcap-like Tribrachidium heraldicum, one of the only known animals to have triradial symmetry.

Artist's reconstruction of Obamus coronatus [Image licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com/), Obamus NT, CC BY-SA 4.0]

There's a misconception about evolution -- that it's linear and progressive, that one form supersedes another in some kind of stepwise fashion based upon an identifiable "improvement," such as increase in speed, defensive or offensive capabilities, ability to access food, or intelligence.  While you can find examples where this appears to have happened, there's a large measure of the chaotic involved in the history of life.  Not only do we see sudden and drastic changes in the climate and environmental conditions -- which, after all, are the biggest drivers of selective pressure -- random occurrences like volcanic eruptions and meteorite strikes can create a situation where extinction had way less to do with poor evolutionary fitness than simply being in the wrong place at the wrong time.

The Ediacaran Assemblage seems to have been on the unfortunate end of that particular equation.  As I mentioned, the majority of them apparently left no descendants, not only today but even by the beginning of the next geological era.  None of the bizarre Ediacaran life forms appear in the early Cambrian; the dominant animals five hundred million years ago show almost no resemblance to their predecessors seventy million years earlier.

In fact, the subject comes up because of a paper a few weeks ago in Geology suggesting that the wipeout of the Ediacaran Assemblage represents the Earth's first known mass extinction (not counting the Great Oxidation Event, of which the effect on life was uncertain but probably enormous).  The new study uses recently-uncovered late Precambrian fossil beds that greatly add to the described Ediacaran biota, and the analysis found that we may well have been drastically underestimating the magnitude of the crash.

The researchers' data shows that what is known as the Kotlin Crisis, the biotic collapse that took out pretty much all of the Ediacaran life forms, may have wiped out as much as eighty percent of life on Earth.  This easily places it amongst what paleontologists Jack Sepkoski and David Raup called the "Big Five" extinction events (the Late Ordovician, Late Devonian, Permian-Triassic, End Triassic, and Cretaceous-Tertiary extinctions).  In fact, if the eighty percent number is correct, it would be in second place -- handily beating the sixty-odd percent of life destroyed in the famous Cretaceous-Tertiary extinction, and exceeded only by the cataclysmic Permian-Triassic "Great Dying."

So, what caused the Kotlin Crisis?  At the moment, it's uncertain.  It may have been a series of unfortunate events, including climate shifts, changes in oxygenation of the ocean, volcanic eruptions, and possibly the evolution of carnivory, but honestly, we're not sure.  There are few enough rock outcrops of that age available to study that any determination is likely to be slow in coming.

But what's certain is that these (very) distant cousins of ours represent a road not taken -- a branch of the vast evolutionary tree of life on Earth that led to no descendants.  It always makes me wonder what would have happened had they survived, and perhaps outcompeted, the bilateral, mobile forms that superseded them, and who ultimately became our ancestors.  If -- in evolutionary biologist Stephen Jay Gould's evocative words -- we could re-run the tape, who would now be the dominant life forms on Earth?

Wouldn't be us, that's for damn sure.  Maybe something like H. P. Lovecraft's bizarre pentaradial "Great Old Ones:"

[Image licensed under the Creative Commons Tom Ardans - blog - Facebook, Old One by Tom Ardans, CC BY-SA 3.0]

I can virtually guarantee that whatever it would have been, it'd be something so strange to our eyes that it would give even Darwin pause, despite all his blithe talk about "many forms most beautiful and most wonderful."

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The shifting sands

In H. P. Lovecraft's wildly creepy story "The Shadow Out of Time," we meet a superintelligent alien race called the Yith who have a unique way of gathering information.

The Yith, who lived in what is now Australia's Great Sandy Desert some 250 million years ago, are capable of temporarily switching personalities with other intelligent beings throughout the cosmos and from any time period.  While the consciousness of the kidnapped individual is residing in its temporary Yith body, it enjoys the freedom to learn anything it wants from the extensive library of information the Yith have gleaned -- as long as the individual is willing to contribute his/her own knowledge to the library.  The main character, early twentieth century professor Nathaniel Peaslee, is switched, and while he is living with the Yith he meets a number of luminaries whose personalities have also been swiped, including:

• Titus Sempronius Blaesus: a Roman official from 80 B.C.E.
• Bartolomeo Corsi: a twelfth-century Florentine monk
• Crom-Ya: a Cimmerian chief who lived circa 15,000 B.C.E.
• Khephnes: a Fourteenth Dynasty (circa 1700 B.C.E.) Egyptian pharaoh
• Nevil Kingston-Brown: an Australian physicist who would die in 2518 C.E.
• Pierre-Louis Montagny: an elderly Frenchman from the time of Louis XIII (early seventeenth century)
• Nug-Soth: a magician from a race of conquerors in16,000 C.E,
• S'gg'ha: a member of the star-headed "Great Race" of Antarctica, from a hundred million years ago
• Theodotides: a Greco-Bactrian official of 200 B.C.E.
• James Woodville: a Suffolk gentleman from the mid-seventeenth century
• Yiang-Li: a philosopher from the empire of Tsan-Chan, circa 5000 C.E.

Compared to most of the gory dismemberments other Lovecraftians entities were fond of, the Yith are remarkably genteel in their approach.  Of course, it's not without its downside for the kidnapped individual; not only do they lose control over their own bodies for a period up to a couple of years, they experience serious disorientation (bordering on insanity in some cases) upon their return to their own bodies.

Nevertheless, it's a fantastic concept for a story, and I remember when I first read it (at about age sixteen) how taken I was with the idea of being able to meet and talk with individuals from both past and future, not to mention other species. But what struck me most viscerally when I read it was when Peaslee, in the Yith's body, describes what he sees surrounding the library.

It's a tropical rain forest.  What now is a barren desert, with barely a scrap of vegetation, was a lush jungle:

The skies were almost always moist and cloudy, and sometimes I would witness tremendous rains.  Once in a while, though, there would be glimpses of the Sun -- which looked abnormally large -- and the Moon, whose markings held a touch of difference from the normal that I could never fathom.  When -- very rarely -- the night sky was clear to any extent, I beheld constellations which were nearly beyond recognition.  Known outlines were sometimes approximated, but seldom duplicated; and from the position of the few groups I could recognize, I felt I must be in the Earth's southern hemisphere, near the Tropic of Capricorn.

The far horizon was always steamy and indistinct, but I could see that great jungles of unknown tree ferns, Calamites, Lepidodendron, and Sigillaria lay outside the city, their fantastic fronds waving mockingly in the shifting vapors...  I saw constructions of black or iridescent stone in glades and clearings where perpetual twilight reigned, and traversed long causeways over swamps so dark I could tell but little of their towering, moist vegetation.

[Image licensed under the Creative Commons Carl Malamud, Cretaceous Diorama 2, CC BY 2.0]

I think it's the first time I'd really gotten hit square between the eyes with how different the Earth is now than it had been, and that those changes haven't halted. In the time of Lovecraft's Yith, 250 million years ago, where I am now (upstate New York) was underneath a shallow saltwater ocean.  Only a hundred thousand years ago, where my house stands was covered with a thick layer of ice, near the southern terminus of the enormous Laurentide Ice Sheet.  (In fact, the long, narrow lakes that give the Finger Lakes Region its name were carved out by that very glacier.)

I was immediately reminded of that moment of realization when I read a paper in Nature called "Temperate Rainforests Near the South Pole During Peak Cretaceous Warmth," by a huge team led by Johann Klages of the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar und Meeresforschung, of Bremerhaven, Germany.  Klages's team made a spectacular find that demonstrates that a hundred million years ago, Antarctica wasn't the windswept polar desert it currently is, but something more like Lovecraft's vision of the site of the prehistoric library of Yith.  The authors write:

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume.  In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions.  Here we use a sedimentary sequence recovered from the West Antarctic shelf—the southernmost Cretaceous record reported so far—and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian–Santonian age (92 to 83 million years ago).  This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores.  A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120–1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.

It's a stunning discovery from a number of perspectives.  First, just the wonderment of realizing that the climate could change so drastically.  Note that this wasn't, or at least wasn't entirely, because of tectonic movement; the site of the find was still only eight degrees shy of the South Pole even back then.  Despite that, the warmth supported a tremendous assemblage of life, including hypsilophodontid dinosaurs, labyrinthodontid amphibians, and a diverse flora including conifers, cycads, and ferns.  (And given that at this point Antarctica and Australia were still connected, Lovecraft's vision of the home of the Yith was remarkably accurate.)

So, if it wasn't latitude that caused the warm climate, what was it?  The other thing that jumps out at me is the high carbon dioxide content of the atmosphere back then -- 1,000 parts per million.  Our current levels are 410 parts per million, and going up a steady 2.5 ppm per year.  I know I've rung the changes on this topic often enough, but I'll say again -- this is not a natural warm-up, like the Earth experienced during the mid-Cretaceous.  This is due to our out-of-control fossil fuel use, returning to the atmosphere carbon dioxide that has been locked up underground for hundreds of millions of years.  When the tipping point will occur, when we can no longer stop the warm up from continuing, is still a matter of debate.  Some scientists think we may already have passed it, that a catastrophic increase in temperature is inevitable, leading to a complete melting of the polar ice caps and a consequent rise in sea level of ten meters or more.

What no informed and responsible person doubts any more is that the warm-up is happening, and that we are the cause.  People who are still "global warming doubters" (I'm not going to dignify them by calling them skeptics; a skeptic respects facts and evidence) are either woefully uninformed or else in the pockets of the fossil fuel interests.

I don't mean to end on a depressing note.  The Klages et al. paper is wonderful, and gives us a vision of an Earth that was a very different place than the one we now inhabit, and highlights that what we have now is different yet from what the Earth will look like a hundred million years in the future.  It brings home the evocative lines from Alfred, Lord Tennyson's wonderful poem "In Memoriam:"

There rolls the deep where grew the tree.
O Earth, what changes hast thou seen?
There where the long road roars hath been
The stillness of the central sea.
The hills are shadows, and they flow
From form to form, and nothing stands;
They melt like mist, the solid lands,
Like clouds, they shape themselves and go.

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Pressing reset

Although you don't tend to hear much about it, the Ordovician Period was a very peculiar time in Earth's history.

From beginning (485 million years ago) to the end (444 million years ago) it experienced two of the biggest global climatic swings the Earth has ever seen.  In the early Ordovician the climate was a sauna -- an intense greenhouse effect caused the highest temperatures the Paleozoic Era would see, and glacial ice all but vanished.  Life was abundant in the shallow seas.  One of the dominant groups were the conodonts:

[Image licensed under the Creative Commons Prehistorica, Panderodus unicostatus, CC BY-SA 4.0]

Those of you who know your fish might guess that conodonts like Panderodus were related to modern lampreys, and you're right.  But it took a really long time to figure that out.  Their soft bodies didn't fossilize well, so about all that we had were the cone-shaped teeth that gave them their name.  In fact, those teeth are the most common fossils in Ordovician sedimentary rocks, so we knew whatever grew them must have been abundant -- but it took a while to determine what kind of animal they came from.

So things were warm, humid, with tropical conditions virtually pole to pole.  Then... something happened.  We're still not entirely sure what.  Part of it was undoubtedly simple plate tectonics; the supercontinent of Gondwana was gradually moving toward the South Pole.  There's some evidence of a large meteorite strike, or possibly more than one.  But whatever the cause, by the end of the Ordovician, glaciers covered much of what is now Africa and South America, resulting in a drastic drop in sea level and a massive extinction that wiped out an estimated sixty percent of life on Earth.  

At this point, life was confined to the oceans. The first terrestrial plants and fungi wouldn't evolve until something like twenty million years after the beginning of the next period, the Silurian, and land animals only followed after that.  As the Ordovician progressed, and more and more ocean water became locked up in the form of glacial ice, much of what had been shallow, temperate seas dried up to form cold, barren deserts.  And that was all there was on land -- thousands of square kilometers of rock, sand, and ice, without a single living thing larger than bacteria to be found anywhere.

Then, the climate reversed again.  The seas flooded back in, and the warmer, sulfur-rich, oxygen-poor water upwelling from the bottom knocked out about twenty percent of the cold-adapted survivors.  By the time the period ended, the Earth had a seriously impoverished biosphere, with something like fifteen percent of the original biota making it through the double-whammy.

But what survived this pair of climate swings was to shape Earth's biological history forever.  Because it included primitive vertebrates with paired jaws -- the gnathostomes -- which became the ancestors of 99% of modern vertebrate animals, including ourselves.

The reason this comes up is some new research out of the Okinawa Institute of Science and Technology that analyzed thousands of fossils from species that made it through the Late Ordovician bottleneck -- and an equal number of those that didn't.  And they found two interesting patterns.  First, the survivors were mostly species that found their way into refugia -- small, isolated pockets of ecosystems with (slightly) more hospitable conditions that allowed them to squeak their way through the worst times.  Second, each of the major extinction pulses was followed by dramatic diversification, as the surviving populations expanded into niches vacated by the ones that weren't so fortunate.

"We pulled together two hundred years of late Ordovician and early Silurian paleontological research," said study lead author Wahei Hagiwara.  "By reconstructing the ecosystems within these refugia, we were able to measure changes in genus-level diversity over time.  Our analysis revealed a steady but striking rise in jawed vertebrate diversity following the extinction.  And the trend is clear -- the mass extinction pulses led directly to increased speciation after several millions of years."

As Ian Malcolm so accurately put it, "Life, uh, finds a way."

A couple of other things strike me about this research, though.

The first is how contingent our existence here is.  Evolutionary biologist Stephen Jay Gould wrote a provocative piece about "replaying the tape of life," coming to the conclusion if you were to start over from the beginning, so much of the path of evolution has rested on chance occurrences that the chances of it turning out exactly the same way is nearly zero.  In a situation like the Late Ordovician Mass Extinction, which assortment of species made it into the few hospitable refugia must have had as much to do with luck as with being well-adapted; had a different set of populations survived, life today almost certainly would look very different.

The second is the fact that both of the Ordovician climate swings were far slower than what we're currently doing to the environment.  Like, hundreds of times slower.  The second one, in fact -- the warm-up and subsequent melting of polar ice -- was almost certainly a very gradual rebound toward the greenhouse conditions that were to pertain by the mid-Silurian.  We're talking about something on the order of ten million years to go from cool to warm.

What we're doing now has taken only a couple of hundred.

What happened in the Late Ordovician should be a wake-up call for us.  Yet somehow, we arrogant humans think we're immune to the effects of our out-of-control fossil fuel burning.  We have a striking fossil record documenting the terrible effects of rapid climate change in prehistory; at the moment, mostly what we seem to be doing is saying, "Yeah, but it won't happen to us, 'cuz we're special."

So that's our cautionary tale for today.  The climate change deniers are fond of saying, "Earth's climate has changed many times before now," and almost never add, "... and when it did, enormous numbers of species went extinct."  And the difference, too, is that the natural fluctuations (such as those caused by plate movement, asteroid strikes, and changes in insolation) aren't something we could control even if we wanted to, but what we're doing now is entirely voluntary.

And until the people in charge realize that addressing climate change is in all of our best interest, I'm afraid our path forward is not likely to change.

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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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