News from Afar

I've written here before about the fact that the continents are in motion, something that is only not staggering because we've all known about it since ninth grade Earth Science class.  You can easily see why it took so long to accept.  First, the motion is so slow that it was, for most of human history, beyond the limitations of the technology available at the time to measure directly.  Second, it's just hard to imagine.

Continents?  Moving in solid rock?  What?

But move they do, and it's because if you go down far enough, the rock isn't solid.  Get into the upper mantle, and it's the consistency of taffy, so it flows, pushed by subterranean convection currents.  Those currents create drag forces on the undersides of the tectonic plates, shifting them around.  Although this is an oversimplification, in general, there are three ways that plates can move relative to each other:

• Convergent zones, where plates come together.  When thin, brittle oceanic plates are pushed toward each other, one usually bends and slides under the other at a thrust fault or subduction zone; the subducted plate and the sediment riding on it eventually melt, and the hot, water-rich magma rises to form chains of volcanoes parallel to the fault.  Examples are the Japan Trench and the Sumatra Trench.  When an oceanic plate collides with a thick, cold continental plate, you still get volcanoes boring their way up through the continent -- this is the origin of the Cascade Range.  If it's two continental plates colliding, the rock simply crumples up to form mountains -- such as what is happening in the Alps and Himalayas,
• Divergent zones, where plates move apart.  This is what's happening along the Mid-Atlantic Ridge, and is why the island of Iceland is volcanic -- the eastern and western halves of the island are moving apart, and new basaltic lave bubbling up to fill the gap.

A photograph I took at Meradalir Volcano in Iceland, August 2022

• Strike-slip faults, or transform faults, which occur when plates slide in opposite directions parallel to the fault.  Examples are the San Andreas, Hayward, and Elsinore Faults in California, and the Alpine Fault in New Zealand.

All of these movements can significantly transform the shapes and positions of the continents -- you probably know that 250 million years ago, most of the Earth's land masses were assembled into a giant supercontinent (Pangaea), and the seas into a massive superocean (Panthalassa), with huge consequences to the climate.  Fascinating to realize, though, that Pangaea was only the most recent of the supercontinents; geologists believe that the same lumping-it-all-together occurred at least three or four times before then.

And the reverse can happen, too, when a divergent zone forms underneath a continent, and it tears the land mass in two.  In fact, this is the reason the topic comes up today; a paper last week in Nature Geoscience about the Afar Triple Junction, the point where three faults meet at one point (the Red Sea Rift, the Aden Ridge, and the East African Rift).  Geologists have found that underneath this region, there's a mantle plume -- an upwelling of very hot magma -- that is pulsing like a giant beating heart, driving convection that will eventually tear Africa in two, shearing off a chunk from Ethiopia to Mozambique and driving it east into the Indian Ocean.

[Image licensed under the Creative Commons Val Rime, Tectonic African-Arabian Rift System, CC BY-SA 4.0]

"We have found that the evolution of deep mantle upwellings is intimately tied to the motion of the plates above," said Derek Keir, of the University of Southampton, who co-authored the study.  "This has profound implications for how we interpret surface volcanism, earthquake activity, and the process of continental breakup...  The work shows that deep mantle upwellings can flow beneath the base of tectonic plates and help to focus volcanic activity to where the tectonic plate is thinnest.  Follow on research includes understanding how and at what rate mantle flow occurs beneath plates."

The formation of a new sea -- and the consequent turning of much of east Africa into an island -- isn't exactly what I'd call "imminent;" it's predicted that the Red Sea will breach the Afar Highlands and flood the lowest points of the rift (much of which is already below sea level) in something like five million years.  The region will be highly tectonically active throughout the process, however, and there'll be enough volcanoes and earthquakes in the meantime to keep us interested.

It's a good reminder that although mountains and oceans have been a symbol of something eternal and unchanging, in reality everything is in flux.  It recalls to mind the lines from Percy Shelley's evocative poem "Mont Blanc," which seems a fitting way to end:

Yet not a city, but a flood of ruin
Is there, that from the boundaries of the sky
Rolls its perpetual stream; vast pines are strewing
Its destin’d path, or in the mangled soil
Branchless and shatter’d stand; the rocks, drawn down
From yon remotest waste, have overthrown
The limits of the dead and living world,
Never to be reclaim’d.  The dwelling-place
Of insects, beasts, and birds, becomes its spoil;
Their food and their retreat for ever gone,
So much of life and joy is lost.  The race
Of man flies far in dread; his work and dwelling
Vanish, like smoke before the tempest’s stream,
And their place is not known.  Below, vast caves
Shine in the rushing torrents’ restless gleam,
Which from those secret chasms in tumult welling
Meet in the vale, and one majestic River,
The breath and blood of distant lands, for ever
Rolls its loud waters to the ocean-waves,
Breathes its swift vapours to the circling air.

****************************************

Mysterious mountains

It's amazing how far human knowledge has come in only a hundred years.

Consider the following about the year 1924:

• This is the year we would figure out that there are other galaxies beyond the Milky Way; before this, astronomers thought the Milky Way was all there was.  They called the galaxies they knew about (such as Andromeda and the Whirlpool Galaxy) "nebulae" (Latin for "clouds") and thought they were blobs of dust within our own galaxy.  This marks the moment we realized how big the universe actually is.
• In 1924, the quantum nature of reality was still unknown; the first major papers by Heisenberg, Schrödinger, and Born would come out next year.
• It'd be another four years before the first antibiotic -- penicillin -- was discovered.
• It'd be five years before Edwin Hubble announced his discovery of red shift, which showed the universe is expanding and led to the Big Bang model of cosmology.
• We'd have another seventeen years before we'd see the first electron micrograph of a virus; before that, it was known they caused disease, but no one knew what they were or had ever seen one.
• It'd be another twenty years before DNA was shown to be the genetic material, and a good twenty years after that when Franklin, Watson, and Crick figured out its structure and the basics of how it works.
• The first papers outlining the mechanics of plate tectonics were still forty years in the future; at this point, the only one who championed the idea that the continents moved was German geologist and climatologist Alfred Wegener, who was pretty much laughed out of the field because of it (and ultimately died in 1930 on an expedition to Greenland).

It's the last one that's germane to our topic today, which is a largely-unexplained (and massive) feature of North Africa that goes to show that however far we've come, there are still plenty of things left for the scientists to explain.  It's called the Tibesti Massif, and largely lies in the far north of the country of Chad, with a bit spilling over the southern border of Libya.

It's a strange, remote, and forbidding landscape:

[Image is in the Public Domain courtesy of photographer Michael Kerling]

What's peculiar about it -- besides the fact that it looks like the "desert planet" set from Lost in Space -- is that its terrain was largely created by volcanism, despite the fact that it lies smack in the center of one of those "stable continental cratons" I talked about in my previous post.  It's got a very peculiar geology -- the basement rock is Precambrian granite, over which there's a layer of Paleozoic sandstone, but above that is a layer of basalt which is in some places three hundred meters thick.  Basalt is one of those mafic rocks I mentioned; iron-rich, silica-poor, and ordinarily associated with seafloor rift zones like Iceland and deep-mantle hotspots like Hawaii.  But over that are felsic rocks like dacite, rhyolite, and ignimbrite, which are usually found in explosive, subduction zone volcanoes like the ones in the Caribbean, Japan, and Indonesia.

What's odd about all this is that there's no mechanism known that would generate all these kinds of rocks from the same system.  The current guess is that there was a mantle hotspot that started in the late Oligocene Epoch, on the order of twenty-five million years ago, that has gradually weakened and incorporated lower-density continental rocks as the upwelling slowed, but the truth is, nobody really knows.

It's still active, too.  The Tibesti Massif is home to hot springs, mud pools, and fumaroles, some of which contain water at 80 C or above.

So we've got a volcanic region in the southern Sahara where, by conventional wisdom, there shouldn't be one, with a geology that thus far has defied explanation.  Some geologists have tried to connect it to the Cameroon Line or the East African Rift Zone, but the truth is, Africa is a much bigger place than most people think it is, and it's a very long way away from either one.  (It's about three thousand kilometers from the northernmost active volcanoes in both Cameroon and Ethiopia to the southern edge of the Tibesti Massif; that's roughly the distance between New York City and Denver, Colorado.  So connecting Tibesti to either the Cameroon Line or the East African Rift is a bit like trying to explain the geology of Long Island using processes happening in the Rocky Mountains.)

And the problem is, figuring out this geological conundrum isn't going to be easy.  It's one of the most remote and difficult-to-access places on Earth, hampered not only by the fact that there are virtually no roads but the one-two punch of extreme poverty and political instability in the country of Chad.  So even getting a scientific team in to take a look at the place is damn near impossible.  The geologists studying the region have resorted to -- I swear I'm not making this up -- using comparisons to research on the geology of volcanoes on Mars, because even that is easier than getting a team into northern Chad.

The idea that we have a spot on the Earth still so deeply mysterious, despite everything we've learned, is both astonishing and thrilling.  Here we sit, in 2024, as arrogantly confident we have a bead on the totality of knowledge as the people did back in 1924, despite the fact that history has always shown such confidence in our understanding is unfounded.  The reality is humbling, and far more exciting.  As Carl Sagan put it, "Somewhere, something amazing is waiting to be known."

I wonder what the next hundred years will bring, and if the people in 2124 will look back at us with that same sense of "how could they not have known that?"

Onward -- into the great unknown!

****************************************

The honey hunters

One of the things I learned from 32 years of teaching biology is that many non-human animals are way smarter than we give them credit for -- and its corollary, which is that we humans are not as far separated from the rest of the natural world as many of us would like to think.

A charming piece of research in Science this week illustrates this point brilliantly.  It's about a species of African bird, the Greater Honeyguide (its scientific name, which I swear I'm not making up, is Indicator indicator).  It's found in open woodland in most of sub-Saharan Africa, and has a very specialized diet -- it lives on bee eggs, larvae, and wax (it's one of the few known animals that can digest wax).

Illustration of a Greater Honeyguide by Nicolas Huet (1838) [Image is in the Public Domain]

Because of its diet, local residents have developed a mutualistic relationship with honeyguides, a relationship that is what gives the birds their common name.  People living in the region listen for the bird's call and then follow it to find the bees' nests it was attracted to.  The people tear open the nests and take the honey -- and the bird gets the larvae and the wax.  Many cultures that live in the honeyguides' range have developed specific calls to attract the birds when they're ready to go on a honey hunt.

The study, led by ecologist Claire Spottiswoode of the University of Cambridge, looked at the fact that honeyguides seem to learn the specific calls used by the people they live near.  Initially, it was uncertain if the people had figured out what the birds responded to, or if the reverse was true and the birds had learned what noises the people made.  So she and her team decided to test it; they used recordings of individuals from two cultures that are known to use honeyguides, the Hadza of Tanzania and the Yao of Malawi and Mozambique.  The Hadza employ a complex series of whistles to summon their helpers, while the Yao make a "brrr-huh" sound.

Both signals work just fine, but only in particular regions.  When a recording of the Hadza signal is played in Malawi, or a recording of the Yao signal is played in Tanzania, the birds don't respond.  The birds have evidently learned to recognize the specific calls of their partners in the region where they live -- and don't "speak the language" used elsewhere.

Spottiswoode's team also found there are two places where the symbiotic relationship is falling apart.  In more urban areas, where commercial sugar is widely available, there are fewer people engaged in honey hunting, so the birds have decided they're better off working as free agents.  Even more interesting, in some areas in Mozambique, the Yao discovered that if they destroy the wax and the rest of the hive, the honeyguides will stay hungry and look for other nests.  But... the birds are learning that their human partners are stiffing them, and they're becoming less likely to respond when called, so the human honey hunters are having less overall success.

So even birds can recognize when they're getting a raw deal, and put a stop to it.

The more we find out about the other life forms with which we share the planet, the more commonality we find.  Everything in the natural world exists on a continuum, from our physiology and our genetics to characteristics many thought of as solely human traits, like emotion, empathy, and intelligence.

So be careful when you throw around terms like "bird-brain" -- they're not as far off from us as you might like to believe.

****************************************

The exploding lakes of Cameroon

Dear Readers: I'm going to be taking a couple of days off just to catch my breath.  Keep those topics coming!  The next Skeptophilia post will be on Wednesday, October 11.  Cheers!

************************************

Prompted by yesterday's post, about the bizarre, beautiful, and deadly hot springs of Dallol, Ethiopia, a reader commented, "Yes, but have you heard about the exploding lake of Cameroon?"

Being a bit of a geology buff, I had indeed, but I don't believe I've ever written about them here.  So, without further ado, meet Lake Nyos:

Its peaceful appearance belies its behavior.  It's a crater lake, a water-filled depression in the middle of the remnant of a (in this case, very active) volcano.  Lake Nyos is part of the Oku Volcanic Field, a relatively poorly-studied geological feature in the Cameroon Line.  The latter is (as you'd guess) a nearly straight line of faults and volcanoes running the entire length of Cameroon from southwest to northeast.  This, in turn, appears to be part of the Central African Shear Zone, a region of unexplained thin crust and high torque that is prone to catastrophic ruptures.

So at first glance, it seems like nothing more than a seismically-active fault zone, which (after all) are nothing unusual.  But the Oku Volcanic Field, and the part of it under Lake Nyos, has a feature that is nothing short of wild.

The magma underneath Oku holds tons (literally) of dissolved carbon dioxide.  Why this is so is not understood, but it's probable that the magma has been in contact with layers of carbonate rocks, such as limestone.  When magma contacts carbonates, the intense heat breaks them down -- the metal ions (usually calcium and magnesium) bond to the aluminum and silicon oxides present in the magma, forming pyroxenes, while the carbon is released as carbon dioxide.  

As long as this carbon dioxide is under pressure, it remains dissolved (whether in the magma or in water the magma is in contact with), and all is well.  But the problem with Lake Nyos is twofold.  First, the bottom of the lake is very deep, and has seams and cracks extending far down toward the magma chamber.  Second, its water is highly stratified -- the top is warm and buoyant, the lowest layers cold and dense.

And it's into that cold, dense layer at the bottom that the carbon dioxide has been seeping for centuries.

The result is something like a bottle of champagne.  Keep the cork on, and nothing happens.  Shake it, then pop the cork...

The shake came with a relatively small underwater landslide on August 21, 1986.  This jostled the water in the lake -- as you'd expect -- and in an ordinary lake, this probably wouldn't have caused anything other than some bottom mud being stirred to the surface.  But remember that the lower strata of the water column in Lake Nyos were supercharged with carbon dioxide, with the pressure of all the upper layers keeping it in solution.  As soon as it started to rise, the dissolved carbon dioxide came bubbling out.

Bubbles expand as they rise.  Disturbing the water more, and bringing more water up.  Releasing more carbon dioxide.  The result?

The lake exploded.

An enormous blast of carbon dioxide blew out of the lake, and as carbon dioxide is heavier than air, it filled the valley and then poured over the margin, rushing downhill at an estimated one hundred kilometers an hour.  Within minutes, over seventeen hundred people living in villages downhill from the valley rim had been smothered to death.

Since then, efforts have been made toward degassing the lake -- running vertical pipes all the way down to the bottom, attached to pumps the bring the supersaturated water to the surface and allow the carbon dioxide to fountain off gradually and harmlessly.  How effective this will be in preventing another deadly explosion is unknown -- and there are at least two other lakes, Lake Monoun in Cameroon and Lake Kivu, between the Democratic Republic of the Congo and Rwanda, that have been shown to have supersaturated bottom strata as well.

Lake Kivu, by the way, is two thousand times bigger than Lake Nyos.

So that's a little alarming.  Especially given how many people live near these bodies of water.  It's the usual problem; volcanic soils are good for agriculture, and the gas eruptions don't happen that often... and people have short memories.

Yet another reason I'm glad I live where I do.  The climate may be a little dismal -- it's been described as nine months of expectations followed by three months of disappointments -- but I'll take that over exploding lakes any day.

****************************************

The global melting pot

One of the shakiest concepts in biological anthropology is race.

Pretty much all biologists agree that race, as usually defined, has very little genetic basis.  Note that I'm not saying race doesn't exist; just that it's primarily a cultural, not a biological, phenomenon.  Given the fact that race has been used as the basis for systematic oppression for millennia, it would be somewhere beyond disingenuous to claim that it isn't real.

The problem is, determination of race has usually been based upon a handful of physical characteristics, most often skin, eye, and hair pigmentation and the presence or absence of an epicanthal fold across the inner corner of the eye.  These traits are not only superficial and not necessarily indicative of an underlying relationship, the pigment-related ones are highly subject to natural selection.  Back in the nineteenth and early twentieth century, however, this highly oversimplified and drastically inaccurate criterion was used to develop maps like this one:

The "three great races" according to the 1885 Meyers Konversations-Lexikon 

This subdivides all humanity into three groups -- "Caucasoid" (shown in various shades of blue), "Negroid" (shown in brown), and "Mongoloid" (shown in yellow and orange).  (The people of India and Sri Lanka, shown in green, are said to be "of uncertain affinities.")  If you're jumping up and down saying, "Wait, but... but..." -- well, you should be.  The lumping together of people like Indigenous Australians and all sub-Saharan Africans (based mainly on skin color) is only the most glaring error.  (Another is that any classification putting the Finns, Polynesians, Koreans, and Mayans into a single group has something seriously amiss.)

The worst part of all of this is that this sort of map was used to justify colonialism.  If you believed that there really was a qualitative difference (for that, read genetic) between the "three great races," it was only one step away from deciding which one was the best and shrugging your shoulders at the subjugation by that one of the other two. 

The truth is way more complicated, and way more interesting.  By far the highest amount of genetic diversity in the world is in sub-Saharan Africa; a 2009 study by Jeffrey Long found more genetic differences between individuals from two different ethnic groups in central Africa than between a typical White American and a typical person from Japan.  To quote a paper by Long, Keith Hunley, and Graciela Cabana that appeared in The American Journal of Physical Anthropology in 2015: "Western-based racial classifications have no taxonomic significance."

The reason all this comes up -- besides, of course, the continuing relevance of this discussion to the aforementioned systematic oppression based on race that is still happening in many parts of the world, including the United States -- is a paper that appeared last week in Nature looking at the genetics of the Swahili people of east Africa, a large ethnic group extending from southern Somalia down to northern Mozambique.  While usually thought to be a quintessentially sub-Saharan African population, the Swahili were found to have only around half of their genetic ancestry from known African roots; the other half came from southwestern Asia, primarily Persia, India, and Arabia.

The authors write:

[We analyzed] ancient DNA data for 80 individuals from 6 medieval and early modern (AD 1250–1800) coastal towns and an inland town after AD 1650.  More than half of the DNA of many of the individuals from coastal towns originates from primarily female ancestors from Africa, with a large proportion—and occasionally more than half—of the DNA coming from Asian ancestors.  The Asian ancestry includes components associated with Persia and India, with 80–90% of the Asian DNA originating from Persian men.  Peoples of African and Asian origins began to mix by about AD 1000, coinciding with the large-scale adoption of Islam.  Before about AD 1500, the Southwest Asian ancestry was mainly Persian-related, consistent with the narrative of the Kilwa Chronicle, the oldest history told by people of the Swahili coast.  After this time, the sources of DNA became increasingly Arabian, consistent with evidence of growing interactions with southern Arabia.  Subsequent interactions with Asian and African people further changed the ancestry of present-day people of the Swahili coast in relation to the medieval individuals whose DNA we sequenced.

Note that on the Meyers Konversations-Lexikon map, the Arabians and Persians are considered "Caucasoid," the Indians are "uncertain," while the Swahili are definitely "Negroid."

A bit awkward, that.

It's appalling that we still use an outmoded and scientifically-unsound concept to justify bigotry, prejudice, and discrimination, despite the mountains of evidence showing that there's no biological basis whatsoever to the way race is usually defined.  Easy, I suppose, to hang on to your biases like grim death rather than questioning them when new data comes along.  Not even all that new; the Long study I referenced above was from fourteen years ago.  And hell, the Italian geneticist Luigi Luca Cavalli-Sforza was researching all this back in the 1960s.  Okay, it takes time for people's minds to catch up with scientific discovery, but how much damn time do you need?

The truth is that (1) ultimately, we all come from Africa, (2) since then, we've continued to move around all over the place, and therefore (3) the world is just a huge single melting pot.  Oh, and (4), the result is that we're all of (very) mixed ancestry.  I'm sorry if that makes some people feel squinky, but as I've pointed out before, the universe is under no obligation to align with your preconceived notions about how the world should work.

Time to accept the beauty and complexity of our shared humanity, and stop looking for further ways to divide us.

****************************************

Head hunters

Today's post combines archaeology, mythology, and an etymological mystery -- surely a recipe for something fascinating.

I first ran into the Blemmyes in Umberto Eco's tour-de-force medieval murder mystery The Name of the Rose, where they are described as a race of people living in Africa who have no heads; their faces are in the middle of their torsos.  The topic comes up because of the habit of a manuscript illuminator, Brother Adelmo, who has a habit of adorning his manuscript with fanciful creatures -- not only familiar ones like centaurs and unicorns and dragons, but Cynocephali (dog-headed men), Sciapodes (people with one leg and a huge foot, the inspiration for the Monopods in C. S. Lewis's The Voyage of the Dawn Treader) and... the Blemmyes.

One of the Blemmyes (from a 1556 map by Guillaume de Testu) [Image is in the Public Domain]

So naturally I thought that the Blemmyes were a complete fiction.  (Actually, given the illustration, I hoped they were a complete fiction, because they're freakin' creepy-looking.)

That's why I was pretty surprised when I ran into a story on Science Daily yesterday, about some research out of the Universitat Autonoma de Barcelona that was published last week in the American Journal of Archaeology.  The paper was about the Blemmyes -- who were apparently a real nomadic people that lived in what is now southern and central Egypt during Roman times, and who had their faces on their heads as per the usual human specifications.

What's weirdest about this is that the sources that mention the mythological headless Blemmyes and the ordinary human Blemmyes have almost no overlap; it's as if the authors of one didn't even talk to the authors of the other.  This might be understandable if it was some kind of linguistic coincidence, where two groups of people just happened to use similar-sounding words to describe two entirely different things; but I'm sorry, "Blemmyes" -- not only identical-sounding word, but identical spelling -- is just too weird for me to accept that they're unrelated homophones.  Add to that the fact that the alleged territory of the mythological Blemmyes and the home of the real Blemmyes both were what is now southern Egypt and northern Sudan, and I can't swallow it as some bizarre coincidence.

But the medievalists don't seem to have a good idea of how it happened.  The real Blemmyes, according to third century B. C. E. historian and writer Eratosthenes, were named after one of their ancient kings, King Blemys, but he is unattested elsewhere.  Other linguists have traced the name of the actual people to the Coptic word Ⲃⲁⲗⲛⲉⲙⲙⲱⲟⲩⲓ, Balnemmōui, but tracking the word earlier than that has proven impossible.  What seems certain is that the real Blemmyes are the ancestors of the people who today call themselves the Beja, who live in southern Egypt, Sudan, and Eritrea.

The mythological Blemmyes are even more of a mystery to linguists.  Seventeenth-century French antiquarian Samuel Bochart thought their name came from the Hebrew bly (בלי) "without" and moach (מוח) "brain;" linguist Louis Morié believed it was from the Greek blemma (βλέμμα) "look, glance" and muō (μύω) "close the eyes;" Egyptologist Hans Wolfgang Helck drew its descent from a Coptic word for "blind."

The truth is, no one knows for sure.

Oh, but if you want an even stranger coincidence, the paper in The American Journal of Archaeology about the real Blemmyes is about the discovery in the Egyptian town of Berenike of one of their shrines, within which was entombed fifteen mummified falcons...

... all of which were headless.

You can't make this shit up.

In any case, we're left with a mystery.  The fictional Blemmyes and the real Blemmyes -- and the descendants of the latter, the Beja -- seem to have nothing whatsoever to do with one another, except for a common name and living in approximately the same place.  But there has to be some connection, right?  I dunno, maybe we should be out there looking for real Cynocephali and Sciapodes.  

****************************************

Islands in the sky

About fifteen years ago, I fulfilled a lifelong dream to go to Ecuador, a country I've been fascinated with since I was a kid.  I'm a fanatical birder, and that tiny country is home to no less than one-sixth of the world's nine-thousand-odd bird species, including over three hundred different kinds of hummingbirds.  (Where I live, in upstate New York, we have exactly one, and it's only here in the summer.)

It was when I was reading up on the hummingbirds in the Ecuadorian bird guide before leaving on the trip that I noticed something odd.  A number of the species had extremely narrow ranges.  A good example is the exquisite Violet-tailed Sylph (Aglaiocercus coelestis):

[Image licensed under the Creative Commons Joseph C Boone, Violet-tailed Sylph 2 JCB, CC BY-SA 4.0]

The Violet-tailed Sylph is only found in a narrow band a couple of kilometers wide on the Pacific slope of the Andes.  North-to-south, though, its range spans over sixteen hundred kilometers.  The reason for this bizarre geographical distribution is obvious if you consider the topography; the range of the Violet-tailed Sylph, and the majority of the other hummingbirds, is driven by altitude, so their ranges run in thin strips parallel to the Andes Mountains.  A lot of it has to do with food specialization; they're nectar-feeders, and many of them have bills shaped to fit only a single species of flower.  Many tropical plants are very temperature- and moisture-sensitive, and that depends strongly on altitude, so they have equally restricted ranges.  In the case of the lovely little Sylph, its food sources are mostly found in the cloud forests that run along the mid-slope of the Andes at an elevation of about a thousand meters.

The combination of phenomenal overall biodiversity with extremely narrow ranges that you find in Ecuador draws some parallels with the fascinating ecological model called island biogeography studied in the 1960s by Robert MacArthur and E. O. Wilson.  They were trying to find patterns to explain why some islands (such as Trinidad) have extensive and diverse ecosystems, and others (such as Tristan da Cunha) have very low diversity.  They found two factors that made the most difference; island size and the proximity of the island to the nearest mainland.

The dependence on island size is easy to see; the bigger the island, the more resources there are, and the greater the number of species it can support.  The proximity factor comes from the likelihood of immigration (defined as a new species arriving and becoming established); more distant islands are farther away from a source of new species.  The math gets a little complicated, but the basic gist is that islands end up in an equilibrium between immigration and extinction, and that equilibrium results in a predictably higher number of species on larger islands that are closer to the mainland.

Where this gets interesting is that the mathematical model even works for metaphorical islands -- marshes surrounded by desert, isolated springs and lakes, hydrothermal vents on the floor of the deep ocean, and -- as with our hummingbird -- narrow ecosystems in mountain ranges that are restricted by altitude.  In fact, it's this last one that got me thinking about this topic in the first place; last week, a really cool study by a team led by Martha Kandziora of Charles University (Prague) looked at diversity in African "sky islands," ecosystems high up on mountains that are defined by cold temperatures, low rainfall, and harsh sunlight.  The authors write:

Tropical alpine floras are renowned for high endemism, spectacular giant rosette plants testifying to convergent adaptation to harsh climates with nightly frosts, and recruitment dominated by long-distance dispersal from remote areas.  In contrast to the larger, more recent (late Miocene onward) and contiguous expanses of tropical alpine habitat in South America, the tropical alpine flora in Africa is extremely fragmented across small patches on distant mountains of variable age (Oligocene onward)...  Although some of the mountains are old... most lineages appear to have colonized the afroalpine during the last 5 or 10 My.  The accumulation of species increased exponentially toward the present.  Taken together with recent reports of extremely low intrapopulation genetic diversity and recent intermountain population divergence, this points to a young, unsaturated, and dynamic island scenario.  Habitat disturbance caused by the Pleistocene climate oscillations likely induced cycles of colonization, speciation, extinction, and recolonization.

One of the things driving the study is that these regions are seriously threatened by anthropogenic climate change.  While species like the Violet-tailed Sylph could potentially respond to warming trends by moving farther up-slope, the African sky islands have nowhere to go.  If the climate gets significantly hotter, the great likelihood is that these ecosystems with their unique and bizarre flora will simply disappear.

Tragic to think that we're losing biodiversity and in many cases only poorly understand what's being lost.  Perhaps these odd species with their extreme specialization and tiny ranges don't have much impact on our day-to-day lives, but without them, we would live in a sadly impoverished world.

**************************************

Unity in diversity

It was in my evolutionary biology class in college that I ran into a concept that blew my mind, and in many ways still does.

It was the idea that race is primarily a cultural feature, not a biological or genetic one.  There is more genetic diversity amongst the people of sub-Saharan Africa -- people who many of us would lump together as "Black" -- than there is in the rest of the world combined.  A typical person of western European descent is, our professor told us, closer genetically to a person from Japan than a Tswana man is to the !Kung woman he lives right next door to in Botswana, even though both have dark skin and generally "African features."

To reiterate: I'm not saying race doesn't exist.  It certainly does, and the social, cultural, and political ramifications are abundantly clear.  It's just that what we often think of as race has very close to zero genetic support; we base our racial classifications on a handful of characteristics like skin and eye color, the shape of the nose and mouth, and the color and texture of the hair, all of which can so easily undergo convergent evolution that it triggers us to lump together very distantly-related groups and split ones that lie much closer together on the family tree.

The reason this comes up today is a couple of bits of recent research highlighting the fact that the subject is way more complicated than it seems at first.  The first looks at the fragmentation that happened in Africa, on the order of twenty thousand years ago, that resulted in the enormous genetic diversity still to be found in sub-Saharan Africa today.  By analyzing DNA from both living individuals and the remains of people from long ago, researchers at Harvard University found that this was about the time that our ancestors stopped (for the most part) making extended walkabouts to find mates, and settled into being homebodies.  What triggered this is a matter of conjecture; one possibility is that this was in the middle of the last ice age, it could be that the colder and drier conditions (even in equatorial regions) made food scarcer, so long trips into unknown territory were fraught with more danger than usual.

Whatever the cause, the isolation led to genetic drift.  A general rule of evolutionary biology is that if you prevent genetic mixing, populations will diverge because of the accrual of random mutations, and that seems to be what happened here.  The fact that a Tswana person and a !Kung person (to use my earlier example) are so distinct is because they've been genetically isolated for a very long time -- something facilitated by a tendency to stay at home and partner with the people you've known all your life.

Interestingly, some research last year suggested that there are "ghost lineages" in the human ancestry -- groups that are ancestral to at least some modern humans, but are as yet unidentified from the fossil record.  The one studied in last year's paper were ancestral to the Yoruba and Mende people of west Africa, in which between two and nineteen percent of the genomes come from this ghost lineage -- but the phenomenon isn't limited to them.  The authors found analogous (but different) traces of ghost lineages in people of northern and western European and Han Chinese descent, and the guess is that all human groups have mysterious, unidentified ancestral groups.

The other bit of research that was published last week was an exhaustive study of the genetics of people around the world, with an ambitious goal -- coming up with a genetic family tree for every group of people on Earth. "We have basically built a huge family tree, a genealogy for all of humanity that models as exactly as we can the history that generated all the genetic variation we find in humans today," said Yan Wong of the University of Oxford, who co-authored the study.  "This genealogy allows us to see how every person's genetic sequence relates to every other, along all the points of the genome."

The researchers analyzed 3,609 individual DNA samples representing 215 different ethnic groups, and used software to compare various stretches of the DNA and assemble them using the technique called parsimony -- basically, creating a family tree that requires the fewest random coincidences and ad hoc assumptions.  The result was an enormous genealogy containing 27 million reconstructed common ancestors.  They then linked location data to the DNA samples -- and the program identified not only when the common ancestors probably lived, but where they lived.

I find this absolutely amazing.  Using modern genetic analysis techniques, we can assemble our own family tree, with roots extending backwards tens of thousands of years and encompassing lineages for which we have no archaeological or paleontological records.  With the number of connections the research generated, I have no doubt we'll be studying it for years to come, and have only started to uncover the surprises it contains.

But all part of living up to the maxim inscribed in the Temple of Apollo at Delphi -- γνῶθι σεαυτόν.

"Know thyself."

**************************************

The climatic teeter-totter

I remember how blown away I was when I first saw British science historian James Burke's documentary After the Warming, shortly after its release in 1991.  Its intent was ambitious, to say the least; to trace the effects of climate on humanity, from prehistory up to and beyond the point where (in Burke's words) "the climate stopped doing things to us, and we started doing things to it."

What struck me most is something that at this point is much more widely known; that the periodic warming and cooling had dramatic effects on sea level.  Up during warm periods, down during cold ones, enough to open and close land passages from one place to the other.  The most famous is the "Bering Land Bridge" between what are now Siberia and Alaska, but similar pathways existed across what are now the English Channel and the Gulf of Carpentaria (between Australia and New Guinea).

It shouldn't have been surprising, science geek that I am, but I'd honestly never thought that much about it.  The idea that climatic shifts affected history in such a profound way was an eye-opener.  Take, for example, the Little Ice Age, that started in the mid-fourteenth century and continued into the eighteenth, which had dramatic effects on the climate of northern Europe.  Prior to this, it'd been warm enough that shipping lanes to places like Iceland, Greenland, and Svalbard were open all year long; very quickly, they became impassible ice in the winter, and plagued by devastating storms in the summer.  All of this shut down what had been a thriving avenue for commerce and colonization.  The Icelanders survived okay; but the Greenlanders weren't so lucky.  All of the Viking era Greenland settlements were frozen out by 1400.

The idea was such a poignant one to me -- thinking about what it would be like to be one of the last settlers left alive, knowing you were stranded -- that it inspired me to write a poem called "Greenland Colony 1375," which is not only one of the very few poems I've ever written, but is the only piece of writing I've ever won a prize for -- second place in the 1999 Writers' Journal national poetry contest, an honor that still kid of blows me away when I think about it.

The reason all this comes up is a new study that appeared this week in Proceedings of the National Academy of Science suggesting that major impacts on the human species have been happening for a lot longer than even Burke's documentary covered.  A climatic teeter-totter called the "Wake Circulation" caused a back-and-forth swing of wet and dry from the east to the west part of the African continent, much as the monsoons do on a yearly basis.

But this oscillation has a period of 100,000 years.

That's enough time for an entire ecosystem to form.  Then when the climate changes, what were great adaptations for that habitat suddenly aren't any more, and either you move or you die.  But one other possibility is to live in an ecotone -- the transitional area between two climatic regions.  Since the rainfall didn't disappear from the continent as a whole, just shifted from one side to the other, the ecotone regions didn't move much.  The organisms that made it through the climate shifts tended to be ones that lived in ecotones.

Guess where humanity evolved?

"This alternation between dry and wet periods appeared to have governed the dispersion and evolution of vegetation as well as mammals in eastern and western Africa," said Stefanie Kaboth-Bahr of the University of Potsdam, who led the study.  "The resultant environmental patchwork was likely to have been a critical component of human evolution and early demography as well."

[Image licensed under the Creative Commons Bjørn Christian Tørrissen, Serengeti-African-Elephants, CC BY-SA 3.0]

"We see the archaeological signatures of early members of our species all across Africa," said Eleanor Scerri, of the Max Planck Institute, who co-authored the study.  "Innovations come and go and are often re-invented, suggesting that our deep population history saw a constant saw-tooth like pattern of local population growth and collapse.  Ecotonal regions may have provided areas for longer term population continuity, ensuring that the larger human population kept going, even if local populations often went extinct."

So we may owe our success -- and possibly even our existence -- to our evolving in an ecological borderland, and surviving while other, more specialized, species became extinct when their biome's climate shifted.  

All of this, of course, makes me wonder what the long-term outcome of our current idiotic, la-la-la-la-not-listening climate policy will be.  Will our long-standing flexibility save us -- or will we be, like the tragic last settlers in Greenland, done in by our own short-sightedness?

*************************************

Astronomer Michio Kaku has a new book out, and he's tackled a doozy of a topic.

One of the thorniest problems in physics over the last hundred years, one which has stymied some of the greatest minds humanity has ever produced, is the quest for finding a Grand Unified Theory.  There are four fundamental forces in nature that we know about; the strong and weak nuclear forces, electromagnetism, and gravity.  The first three can now be modeled by a single set of equations -- called the electroweak theory -- but gravity has staunchly resisted incorporation.

The problem is, the other three forces can be explained by quantum effects, while gravity seems to have little to no effect on the realm of the very small -- and likewise, quantum effects have virtually no impact on the large scales where gravity rules.  Trying to combine the two results in self-contradictions and impossibilities, and even models that seem to eliminate some of the problems -- such as the highly-publicized string theory -- face their own sent of deep issues, such as generating so many possible solutions that an experimental test is practically impossible.

Kaku's new book, The God Equation: The Quest for a Theory of Everything describes the history and current status of this seemingly intractable problem, and does so with his characteristic flair and humor.  If you're interesting in finding out about the cutting edge of physic lies, in terms that an intelligent layperson can understand, you'll really enjoy Kaku's book -- and come away with a deeper appreciation for how weird the universe actually is.

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

Becoming human

I think one of the uniting characteristics of the topics that interest me is that they all have something to do with altering our perception of the commonplace reality around us.

This capacity for (in writer Kathryn Schulz's words) "seeing the world as it isn't" led me to writing fiction, but also to the weird and counterintuitive bits of quantum physics, the expansive vision of astronomy, and the fields studying that which no longer exists -- history, archaeology, paleontology.  It's this last one that brings this whole topic up, with a pair of discoveries revealed this week that leave me kind of awestruck.

The first, which came my way from my buddy Andrew Butters over at the wonderful blog Potato Chip Math, is about the discovery in South Africa of a two-million-year-old skull of Paranthropus robustus, a hominin considered a "cousin species" that coexisted with our direct ancestor species Homo erectus.

The find is remarkable from a number of perspectives, not least that a complete skull of any hominin is pretty unusual.  "Most of the fossil record is just a single tooth here and there so to have something like this is very rare, very lucky," said Angeline Leece, who participated in the research.  She added an evocative description of what the world was like when the owner of this skull was still alive and loping around on the African savanna.  "These two vastly different species, Homo erectus with their relatively large brains and small teeth, and Paranthropus robustus with their relatively large teeth and small brains, represent divergent evolutionary experiments,"  Leece said.  "Through time, Paranthropus robustus likely evolved to generate and withstand higher forces produced during biting and chewing food that was hard or mechanically challenging to process with their jaws and teeth — such as tubers.  Future research will clarify whether environmental changes placed populations under dietary stress and how that impacted human evolution."

It's fascinating to imagine what the world was like to these creatures, during a time when there were several intelligent hominin species coexisting.  I remember my evolutionary biology professor making that point; a lot of our attitude that species are these hard-and-fast little cubbyholes comes from the fact that we have no near relatives still alive.  Much more common in the natural world are groups of closely-related species all competing and coexisting.

But it's still a little hard to picture wandering around the place and seeing other human-like, but not-quite-human, animals out there doing their thing.

It also bears keeping in mind that the other animal species they'd have been around weren't like the ones today, either.  This point was driven home by the second discovery revealed this week, of a twelve-thousand-year-old frieze of cliffside paintings in Cerro Azul, Colombia, that show not only the usual assemblage of South American animals -- snakes, alligators, turtles, bats, monkeys, porcupines -- but mastodons, giant sloths, camelids, and some sort of three-toed ungulate with a trunk.

"These really are incredible images, produced by the earliest people to live in western Amazonia," said Mark Robinson, an archaeologist at the University of Exeter, who participated in the study.  "The paintings give a vivid and exciting glimpse in to the lives of these communities.  It is unbelievable to us today to think they lived among, and hunted, giant herbivores, some which were the size of a small car."

A small part of the Cerro Azul frieze

The size, scope, and detail of the drawings is phenomenal.  The paintings were made with ochre, a yellowish or reddish mineral, and cover the cliff face not only for miles horizontally, but for almost twenty meters vertically.  Whatever the purpose of this art -- whether it was purely decorative or had some kind of magical or symbolic significance -- the artists certainly were highly motivated.  Some parts of the frieze would have required ladders or climbing equipment to create, pretty impressive for what was at the time a more or less pre-technological society.

"These rock paintings are spectacular evidence of how humans reconstructed the land, and how they hunted, farmed and fished," said archaeologist José Iriarte, also of the University of Exeter.  "It is likely art was a powerful part of culture and a way for people to connect socially.  The pictures show how people would have lived amongst giant, now extinct, animals, which they hunted."

I find it fascinating that even back then -- at the tail end of the last Ice Age, when merely surviving must have been a challenge -- people were creating art.  And the fact that much of that art was depicting animals no longer extant adds a whole other layer of mind-boggling to the find.  This, and the South African skull discovery, give us a window into understanding how we became human -- how we went from savanna-dwelling apes to intelligent beings who have art, music, literature, science, and technology.

It's a journey that took us from the East African Rift Valley to pretty much every point on the surface of the Earth -- and has driven us along the way to look with wonder into the unknown vastness of the universe.  As Carl Sagan so poignantly put it, "We are a way for the cosmos to know itself."

********************************

One of the most compellingly weird objects in the universe is the black hole -- a stellar remnant so dense that it warps space into a closed surface.  Once the edge of that sphere -- the event horizon -- is passed, there's no getting out.  Even light can't escape, which is where they get their name.

Black holes have been a staple of science fiction for years, not only for their potential to destroy whatever comes near them, but because their effects on space-time result in a relativistic slowdown of time (depicted brilliantly in the movie Interstellar).  In this week's Skeptophilia book-of-the-week, The Black Hole Survival Guide, astrophysicist Janna Levin describes for us what it would be like to have a close encounter with one of these things -- using the latest knowledge from science to explain in layperson's terms the experience of an unfortunate astronaut who strayed too close.

It's a fascinating, and often mind-blowing, topic, handled deftly by Levin, where the science itself is so strange that it seems as if it must be fiction.  But no, these things are real, and common; there's a huge one at the center of our own galaxy, and an unknown number of them elsewhere in the Milky Way.  Levin's book will give you a good picture of one of the scariest naturally-occurring objects -- all from the safety of your own home.

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

The stories the bones tell

The field of forensic anthropology has made amazing strides in the past decades.  Fifty years ago, about all we could count on was identification of gender and suspected ethnic origin, and an estimate of age at death.  Now we are able to use data from bones to reconstruct much of the person's life history.

And sometimes, that history is pretty unpleasant.

One of the first cases in which the entire arsenal of sophisticated analytical techniques was used was "Ötzi," the "Ice Man" of the Alps whose body had been hidden underneath the edge of a glacier in the Italian/Austrian Alps for over five thousand years.  What we now know about Ötzi and his origins is kind of mind-blowing.  From pollen grains found in his clothing, we know he died in early summer, but his last meal contains "einkorn" wheat and sloes, both of which are harvested in the fall -- leading to the conclusion that his people knew how to preserve food over the winter.  He had no less than 61 tattoos, all geometrical and presumably symbolic, perhaps representing magical rituals.  (Or maybe, like me, he had ink just because he thought it was cool.)  He had a copper knife and particles of copper residue in his hair, suggesting he or someone he lived very near was involved in copper smelting.  From an isotopic analysis of his tooth enamel, we even know a bit of his life history -- he appears to have spent his childhood near the present town of Feldthurns, Italy, but at some point in his youth went to a valley fifty kilometers farther north.

Things took a grim turn, however, when the forensic anthropologists started looking into how he died.  Initially it was suspected he'd died in a fall down the hillside, as he had cracked ribs and surface bruises -- possibly resulting in his being knocked unconscious and dying of exposure.  But the truth seems a good bit harsher.  Ötzi has an arrowhead lodged in his upper chest, near the upper lobe of his left lung.  This wasn't an old injury; his shirt had a tear at the same place as the entry wound.  The conclusion from the placement and apparent trajectory of the arrow is that it would have severed arteries in his left pectoral muscle, leading to his death from blood loss.

We humans have been doing bad things to each other for a very, very long time.

If you needed further proof of this, consider the paper in Current Biology that came out two days ago, sent to me by a friend and loyal reader of Skeptophilia, and the reason I've gone into this rather morbid subject today.  In "Origin and Health Status of First-Generation Africans from Early Colonial Mexico," by a team led by Rodrigo Barquera of the Department of Archaeogenetics of the Max Planck Institute for the Science of Human History, we hear about three sixteenth-century skeletons recently found in Mexico that tell a horrific tale of abduction, slavery, and abuse.

The three individuals are clearly of African origin, based not only on skeletal morphology but on tooth-filing patterns that are characteristic of the Fang people of Equatorial Guinea, Cameroon, and Gabon.  Not only that, but one of them had a characteristically African strain of hepatitis B, and another had remnants of the bacteria species (Treponema pallidum ssp. pertinue) that causes the horrific tropical disease yaws (if you choose to investigate further into this disease, do not look at the photographs unless you have a strong stomach -- you have been warned), which is most common in west and central Africa.  In fact, the current presence of yaws in Latin America is almost certainly the result of its having been brought in by the African slave trade.

It only gets worse when you read about the evidence of abuse these skeletons show.  The authors write:

Osteological analyses of the three individuals reveal evidence suggesting a life experience of conflict and hardship.  Individual ML8 SL 150 (SJN001) was found with five buck shots and two healing needles (used in traditional medicine) in the thoracic cavity, as well as gunshot wounds.  Both SJN001 and SJN003 (ML8 SLU9B 296) presented porotic hyperostosis and cribra orbitalia, two pathological changes associated with a skeletal response to nutritionally inadequate diets, anemia, parasitic infectious diseases, and blood loss.  Individual ML8 San José 214 (SJN002) displayed several skeletal changes associated with intense labor and heavy manual activity, including enthesopathies on the clavicle and scapulae as well as osteophytic lipping on the joint surfaces with some additional joint contour deformation at the sternoclavicular joint of the clavicle.  Additionally, he suffered from a poorly aligned complete fracture in the right fibula and tibia, resulting in associated joint changes of the knee, including osteochondritis dissecans of the distal femoral surface with joint contour deformation and associated osteophytic lipping of the articular surface margin.  Furthermore, this individual displayed osteoarthrosis of the lumbar vertebrae in addition to signs of deficient oral health and cut marks on the frontal bone.

"All of us involved in the study were highly touched by the whole story about these three persons, everything that they went through," study lead author Barquera said.  "Knowing that they were first-generation enslaved Africans brings a new perspective on the whole subject because you know they were abducted.  You're seeing all these maltreatment signatures on the bones that came with this abduction, what they suffered for the rest of their lives."

And "the rest of their lives" turned out to be short.  All three of the individuals died in their early or mid-twenties.  Whether they died of disease, malnutrition, murder, or the cumulative abuse they'd suffered isn't known, because they show signs consistent with all possible combinations of the above.

All of it brings home once again the accuracy of Thomas Hobbes's words in his book Leviathan, wherein he characterizes the lives of our ancestors as having been "solitary, poor, nasty, brutish, and short."  It's true that a lot of the poorness and nastiness was circumstantial, and due to bad diet and the prevalence of (then-untreatable) diseases.

But a frightening piece of the "nasty, brutish, and short" part was due to the horrible mistreatment of humans by other humans, often for no better reason than territory, power, rivalries, and tribalism.  I wish I could tell you we've grown beyond all that.  I mean, there's been progress; I wouldn't trade my life here in the 21st century for what Ötzi or the owners of the Mexican skeletons endured.  But that insularity, suspicion, and tribalism is deep within our cultural genes, needing little more than a moment's adversity to bring it to the surface.

Bringing to mind another quote, this one from the Latin playwright Plautus -- Homo lupus homini est (man is a wolf to men).

Which, in my opinion, is slanderous toward the wolves.  They may be fierce, but I've yet to see a wolf enslave another wolf.  On the whole, their society seems a great deal more peaceable than ours is.

***************************************

This week's Skeptophilia book recommendation is an important read for any of you who, like me, (1) like running, cycling, and weight lifting, and (2) have had repeated injuries.

Christie Aschwanden's new book Good to Go: What the Athlete in All of Us Can Learn from the Strange Science of Recovery goes through all the recommendations -- good and bad, sensible and bizarre -- that world-class athletes have made to help us less-elite types recover from the injuries we incur.  As you might expect, some of them work, and some of them are worse than useless -- and Aschwanden will help you to sort the wheat from the chaff.

The fun part of this is that Aschwanden not only looked at the serious scientific research, she tried some of these "cures" on herself.  You'll find out the results, described in detail brought to life by her lucid writing, and maybe it'll help you find some good ways of handling your own aches and pains -- and avoid the ones that are worthless.

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