Resurrection

The environmentalists tell us "extinction is forever," and that certainly seems unarguable.  Once a species is lost, evolution will never recreate it.  You may get something that looks like it; there are numerous examples of Elvis taxa, species that evolved to fit vacated niches and underwent convergent evolution resulting in a similarity to some extinct form.  (The name comes from the huge numbers of Elvis impersonators that have popped up since the original's death in 1977.)  But the sad truth is that the original is gone forever.

The issue, though, can be making certain the species actually is extinct.  There are ongoing efforts to find relic populations of a number of presumed-extinct species (two of the best known are the ivory-billed woodpecker and the thylacine).  Naysayers have criticized the efforts to find these species as nothing more than wishful thinking, but it bears keeping in mind that there is a long list of organisms thought to be extinct that have turned out to be very much alive.

They're called Lazarus taxa, after the biblical character Jesus raised from the dead.  Some of them are astonishing.  The one that always comes to mind for most people is the coelacanth, a crossopterygian fish that was only known from fossils preceding the Cretaceous Extinction sixty-six million years ago, which was discovered living in the Indian Ocean in 1938.  But that's only one of many.  Here's a sampler of Lazarus taxa:

• The South American bush dog (now split into three separate species in the genus Speothos) was only known from some Pleistocene-age bones found in a Brazilian cave, but is now known to have a range from southern Central America all the way to northern Paraguay.  Its reclusive habits and rarity still make it the least-studied canid in the world.

A Brazilian bush dog [Image licensed under the Creative Commons Xerini, Waldhund, CC BY-SA 3.0]

• The nightcap oak (Eidothea hardeniana and E. zoexylocarya), which aren't oaks at all but a member of the Protea family (Proteaceae), were known only from fifteen-million-year-old fossils -- and then a stand of them were discovered growing in a remote part of Australia.  The Royal Botanical Gardens in Sydney has a cultivation program for the two species, which are threatened because the seeds are frequently eaten by introduced mice.

Eidothea hardeniana [Image is in the Public Domain]

• The monito del monte, or colocolo opossum (Dromiciops gliroides), was not only thought to have gone extinct eleven million years ago, it was believed that its entire order (Microbiotheria) was gone as well.  It was found -- alive -- in the temperate bamboo forests of the southern Andes Mountains in 1894, and has no near relatives anywhere in the world.  (The closest are the Australian marsupials, but even those are very distant cousins.)

[Image licensed under the Creative Commons José Luis Bartheld from Valdivia, Chile, Monito del Monte ps6, CC BY 2.0]

• In 1898 a fish was discovered that was a near perfect match to Oligocene-age fossils on the order of twenty-eight million years old.  It's Lignobrycon myersi, and is only known from the Rio Braço and Rio Contas in east-central Brazil.  Somehow, it alone of its genus survived through all of those years and made it down to the present day.

[Image licensed under the Creative Commons Alexandre dos Santos Rodrigues et. al., Lignobrycon myersi specimens (9382613) (cropped), CC BY 4.0]

• The monoplacophorans were a group of mollusks common during the Silurian and Devonian Periods, but were last seen in the fossil record in the mid- to late-Devonian, around 375 million years ago.  After that -- nothing.  Reasonably, biologists thought they'd gone extinct, until live monoplacophorans were discovered in deep water off the west coast of Costa Rica.  Further surveys have found no fewer than thirty-seven different species in deep water across the Pacific.

A live specimen of Neopilina filmed off the coast of Samoa by the 2017 Okeanos Explorer mission [Image is in the Public Domain courtesy of NOAA]

• Even the monoplacophorans don't hold the survival record, though.  That honor goes to Rhabdopleura, which is a graptolite -- a (very) distant relative of chordates known mainly through Cambrian-age fossils.  The last Rhabodopleura was thought to have gone extinct in the mid-Cambrian, five hundred million years ago (and the rest of the group didn't make it past the mid-Carboniferous).  In 1869 they were discovered living in the deep water of the Pacific, and since that time nine living species have been identified.

A drawing of Rhabdopleura normani [Image is in the Public Domain]

While the general rule still applies -- extinction is forever -- it's worth keeping in mind that sometimes we find ourselves in a situation a little like Mark Twain did, resulting in his quip, "Rumors of my death were great exaggerations."  The Earth is a big place, and there are still plenty of poorly-explored regions where we might well have lots of surprises in store.

All of which should be encouraging to the folks out there chasing the ivory-billed woodpecker and thylacine.  Don't give up hope.  If Rhabdopleura could survive for five hundred million years unobserved, surely these two could manage a century or so.

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

The most alien-looking place on Earth

George Wynn Brereton Huntingford was a British anthropologist, linguist, and historian, who traveled widely and was famed for his perceptive observations of societies and cultures.  And if you had to guess which of the many places he traveled during his 77 year life he labeled "the most alien-looking place on Earth," what would you come up with?

His vote was for the island of Socotra, a 132-by-42 kilometer island which lies at at the mouth of the Gulf of Aden.  To the north is the Arabian Sea; to the southwest, the Guardafui Channel separates it from the Horn of Africa.  It's nearer to Africa than to the Arabian Peninsula (232 versus 380 kilometers), but is controlled by the government of Yemen, as much as Yemen's political disaster is currently controlling anything.

Most of Socotra is desert to semi-desert:

[Image licensed under the Creative Commons Rod Waddington from Kergunyah, Australia, Socotra Island (11007223546), CC BY-SA 2.0]

Although it does get more rainfall than either Yemen and Oman (to the north) or Somalia (to the east), so it has a great deal more vegetation than its neighbors:

[Image licensed under the Creative Commons Rod Waddington from Kergunyah, Australia, Wadi, Socotra Island (14495206039), CC BY-SA 2.0]

The main reason for Socotra's uniqueness -- and why evolutionary biologist Lisa Banfield called it "the Galapagos of the Indian Ocean" -- isn't the climate; it's the fact that geologically, it's part of Africa.  During the Miocene Period, about twenty million years ago, Africa and the Arabian Peninsula were joined, but a rift formed that split the two, opening up the Gulf of Aden.  Socotra is a chunk of the Somali Plate that was torn loose and got separated from the rest of the land mass that now forms the easternmost part of Africa.  (Interestingly, the rifting has continued, joining up with a fault system that runs up north through the Red Sea and south into the East African Rift Zone, which one day will tear away a much huger chunk of Africa -- all the way down to Mozambique.)

The issue is that since Socotra's separation from Africa around twenty million years ago, it's been largely isolated, so evolution has veered the community off into its own direction..  This has led to a high degree of endemism -- the fraction of species found nowhere else on Earth.  11% of its bird species, 37% of its plants, 90% of its reptiles, and 95% of its mollusk species are endemic.  One of the most iconic plants is the "dragon's blood tree" (Dracaena cinnabari), which looks like it was invented by Dr. Seuss:

[Image licensed under the Creative Commons Alex38, Dragonblood tree in Socotra 2, CC BY 4.0]

Then, there's the cucumber tree (Dendrosicyos socotranus), which -- as the name would suggest -- is the only species in the cucumber family (Cucurbitaceae) that grows into a tree.  As far as I've heard, though, the fruit isn't edible, which is a good thing, because it'd be a hell of a climb to harvest one for your dinner salad:

[Image licensed under the Creative Commons Gerry & Bonni, Cucumber tree (6407165121), CC BY 2.0]

Like many places with unique and isolated ecosystems, Socotra's oddball assemblage of biota are endangered, from introduced species like cats and rats, from land use by the island's sixty-thousand-odd inhabitants, and from climate change.  The ongoing Yemeni civil war isn't helping, either; the government's priority is certainly not protecting peculiar-looking trees, and the ecotourists whose revenue might help the situation are mostly staying away for their own safety.

In any case, that's one anthropologist's vote for "the most alien-looking place on Earth" -- an island that's geologically African, politically and culturally Arabian, and biologically like nowhere else.  It's a place I'd love to visit one day if the situation calms down.  Adding some bird species to my life list that are found only on one speck of land in the Arabian Sea would be amazing.

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

By any other name...

Scientists have an undeserved reputation for being dry and humorless.

If you doubt the "undeserved" part, consider scientific names.  Because by convention scientific names usually have Greek or Latin roots, they sound pretty sophisticated and fancy -- until you translate them.  The adorable black-footed ferret of the American Rockies is Mustela nigripes, which translates to... "black-footed ferret."  The western diamondback rattlesnake, Crotalus atrox?  Greek for "scary noisemaker."  The name of the mammalian order containing shrews and moles, Eulipotyphla, is kind of insulting.  It means "really fat and blind."  But they only get sillier from there.  How about Eucritta melanolimnetes, a species of amphibian from the Carboniferous Period?  The name means "the real Creature from the Black Lagoon."

And the order of mammals that includes rabbits, Order Lagomorpha?  Translated from Greek, "Lagomorpha" literally means "it's shaped like a bunny."

The privilege of naming a newly-discovered species goes to the discoverer, and if they choose they can name it in honor of someone (it's considered bad form to name it after yourself).  Lots of biologists name species after their teachers or mentors, but the field is wide open.  Entomologists Kelly Miller and Quentin Wheeler named a species of slime-mold beetle after former Vice President Dick Cheney -- whether Agathidium cheneyi was an honor or an insult is open to interpretation.  Some paleontologists working in Madagascar liked to listen to music while they worked, and became convinced that whenever they played Dire Straits, they found lots of new fossils.  Thus, there's a species of Cretaceous dinosaur named Masiakasaurus knopfleri.  (Upon hearing about this, Mark Knopfler allegedly responded, "And people said I was a dinosaur before.")  A genus of carabid beetles, Agra, has a species named Agra schwartzeneggeri.  Terry Erwin, the entomologist responsible for that one, found a number of other Agra species, and thus we have Agra vation, Agra phobia, and Agra cadabra.

You can even name species after fictional characters.  Thus we have a fuzzy mite named Polemistus chewbacca, an Australian moth with marks that resemble a second head named Erechthias beeblebroxi, an Ordovician trilobite named Han solo, a sponge-like fungus from Malaysia named -- I shit you not -- Spongiforma squarepantsii, a cave-dwelling insect from Spain named Gollumjapyx smeagol, and -- my favorite -- a fish from the fjords of New Zealand named Fiordichthys slartibartfasti.

If you get why that last one is fall-out-of-your-chair hilarious, congratulations; you're as big a nerd as I am.

Some are just outright silly.  Consider the Australian wasp discovered by entomologist Arnold Menke in 1977.  He was so delighted at the find that he gave it the scientific name Aha ha.

And I would be remiss in not mentioning a genus of small mollusks named Bittium.  When a related genus of even smaller mollusks was discovered, they named it... you guessed it... Ittibittium.

The reason all this silliness comes up is a discovery that was the subject of a paper in PLOS-One.  Paleontologists working in Brazil found a fossil of a new species of tanystropheid, a group of Triassic dinosaurs with such bizarrely elongated necks that scientists are still trying to figure out how they walked without doing a face-plant.  (One possible answer is that they were aquatic, but that's not certain.)

Tanystropheus longobardicus, which is itself sort of a goofy name.  It means "long, bent thing with a long beard."  I have to wonder how many controlled substances the scientists had partaken of before they came up with that one.  [Image licensed under the Creative Commons Nobu Tamura email: nobu.tamura@yahoo.com http://spinops.blogspot.com/, Tanystropheus NT small, CC BY-SA 4.0]

Anyhow, the new species was christened Elessaurus gondwanoccidens.  The species name isn't so interesting -- it means "from western Gondwana," after one of the supercontinents around during the Triassic Period -- but the genus name is clever.  It plays on the usual -saurus (Greek for "lizard") ending of many genera of dinosaurs, but was actually named for Elessar, one of the many monikers of King Aragorn II from The Lord of the Rings.  Elessar, which means "elf-stone" in J. R. R. Tolkien's wonderful conlang Quenya, was the title Aragorn took after Sauron got his clocks cleaned by Frodo et al. and the former Strider became the King of Gondor.

So that's a look at the deadly serious, dry-as-dust subject of biological taxonomy.  And I haven't even gotten into the off-color ones, which is a whole subject in and of itself.  Suffice it to say that orchid is Greek for "testicle," and there's a mushroom with the scientific name Phallus impudicus ("shameless penis").  I'll leave you to research the rest of that topic on your own.

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

A botanical chameleon

One of the things I love most about science is its capacity to astonish us.

You can be really knowledgeable in a field, and then the natural world slings a curve ball at you and leaves you amazed.  Sometimes these unexpected twists lead to profound leaps in our understanding -- an example is the discovery of the parallel magnetic stripes in igneous rocks along the Mid-Atlantic Ridge leading to the theory of plate tectonics -- but sometimes it's just a fascinating bit of scientific trivia, one of those little things that makes you smile in a bemused sort of way and say, "Science is so cool."

I had a moment like that yesterday.  I taught biology for 32 years and have been interested in plants -- especially tropical plants -- a great deal longer than that.  I have a fine collection of tropical plants, currently jammed into my greenhouse so tightly that I can barely walk through it because the ones who spend the summer on my deck have to be tucked away in a warm place during our frigid winters.  I have bromeliads, cacti, three species of ginger, four different kinds of angel's trumpet (one of which got to be seven feet tall this past summer, and sometimes had twenty giant, peach-colored flowers all blooming at once), a fig tree and a lime tree that produce every year, and two species of eucalyptus.

Among others.

While I wouldn't call myself an expert when it comes to tropical plants, I'm at least Better Than The Average Bear.  So I was startled to run, quite by accident, into an account of a species I had never even heard of -- and even more startled when I found out how truly bizarre and unique this plant is.

It's called the "chameleon vine," and its scientific name is Boquila trifoliolata.  It belongs to a small and rather obscure family of dicots called Lardizabalaceae, which contains forty species found in two places -- southeast Asia and western South America.  (How a group of plants with common ancestry ended up in such widely separated locales is a mystery in and of itself; populations like this are called peripheral isolates and are a perennial puzzle in evolutionary biology.)

Boquila is one of the South American ones, and lives in southern Chile and Argentina.  It's a woody vine whose leaves are composed of three leaflets (thus the plant's species name).  Here's a picture:

[Image licensed under the Creative Commons Inao, Boquila trifoliata [sic], CC BY-SA 2.0]

It's not really much to look at, and you non-botanical types are probably tapping your fingers and saying, "So what?"  But wait till you hear what this plant can do -- and why it merits its common name of "chameleon vine."

Boquila trifoliolata has an extraordinary ability called mimetic polymorphism.  It's capable of altering its leaf shape to mimic a variety of different (unrelated) plants -- including the ones it most commonly twines up as a support.  We're not talking about small differences, either.  It can be glossy or dull, have different petiole lengths, have different leaflet sizes and shapes, and even change whether or not it has serrations or spines along the edge!

This ability, first described in a paper by botanists Ernesto Gianoli and Fernando Carrasco-Urra in Current Biology in 2014, was first attributed to genetic transfer from the host to the vine, a sort of genetic parasitism.  I'll admit that was the first explanation I thought of -- although how a plant could take up DNA from another species and only express the genes related to leaf morphology left me scratching my head a little.  But Gianoli and Carrasco-Urra were able to rule out this possibility, because Boquila can alter its leaf shape without touching the plant it's mimicking.

All it has to do is be nearby.  So it isn't a parasite at all.  The current guess is that Boquila is picking up volatile organic compounds emitted by the other plant, and those are altering gene expression, but those organic compounds have yet to be identified -- nor has any kind of specific mechanism by which that kind of alteration in phenotype could happen.

Less certain still is how it perceives those specific traits in its neighbors so it knows what genes to express, and how.

Even though we still have no idea how Boquila is managing this neat trick, the why is pretty clear.  If it's hiding amongst the foliage of another plant, herbivores can't single it out for a snack.  Gianoli and Carrasco-Urra found that when Boquila is climbing up a non-living support like a chain-link fence, herbivores actually seek it out for browsing.  But when it's camouflaged within another plant's leaves, it can avoid being seen and identified -- and, they found, browsing of its foliage dropped by as much as fifty percent.

Fascinating, isn't it?  And yet despite study, we haven't been able to figure out how the plant evolved this amazing (and apparently unique in the plant world) ability, nor what kind of information it's gleaning that might say, "Okay, time to change color and grow some spikes!"

So yet another example of how science is really freakin' cool.  It also illustrates how every new discovery opens up new avenues for investigation.  The crazy chameleon plant should make it absolutely clear that if you go into science, you'll never be done learning.

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

Birds of a feather

The diversity you find among birds is really remarkable.

There are differences in bill shape, from the weird angled beaks of flamingos, to the longer-on-the-bottom fish skewers of skimmers, to the upswept needle of the avocet, to the absurd (and aptly-named) spoonbills and shoebills, to the pelicans -- about whom my dad taught me a limerick when I was little:

A wonderful bird is the pelican.
His bill can hold more than his bellican.
He can stash in his beak
All his food for the week,
But I really don't see how the hellican.

Yeah, it's kind of obvious where I got my sense of humor from.

Of course, it doesn't end there. The impossibly long toes of the South American jacanas (called "lilytrotters" because they can walk on the floating leaves of waterlilies).  The phenomenal wingspan of the albatross.  The insane plumage of the birds-of-paradise.

And the colors.  Man, the colors!  Even in my decidedly non-tropical home we have some pretty amazing birds.  The first time I saw an Indigo Bunting, I was certain that one of my sons had put a blue plastic bird on the bird feeder just to rattle my chain.  There couldn't be a real bird that was that fluorescent shade of cobalt.

Then... it moved.

But nothing prepared me for the colors I saw on my visits to Ecuador, especially amongst the birds of the tanager family.  There are hundreds of species of tanagers in that tiny little country, and because they often travel in mixed foraging flocks, you can sometimes see twenty or thirty different species in the same tree.  These include the Green-headed Tanager:

[Image licensed under the Creative Commons Lars Falkdalen Lindahl (User:Njaelkies Lea), Green-headed Tanager Ubatuba, CC BY-SA 3.0]

The Black-capped Tanager:

[Image licensed under the Creative Commons Joseph C Boone, Black-capped Tanager JCB, CC BY-SA 4.0]

And the Flame-faced Tanager:

[Image licensed under the Creative Commons Eleanor Briccetti, Flame-faced Tanager (4851596008), CC BY-SA 2.0]

Being a biologist, of course the question of how these birds evolved such extravagant colors is bound to come up, and my assumption was always that it was sexual selection -- the females choosing the most brightly-colored males as mates (in this group, as with many bird species, the males are usually vividly decked out and the females are drab-colored). If over time, the showiest males are the most likely to get lucky, then you get sexual dimorphism -- the evolution of different outward appearances between males and females.  (This isn't always so, by the way.  Most species of sparrows, for example, have little sexual dimorphism, and even experienced birders can't tell a male from a female sparrow by looking.)  More puzzling still is the general trend that tropical birds are more brilliantly-colored than bird species in higher latitudes -- a trend that is yet to be convincingly explained.

The reason this comes up today is two papers that came out last week.  The first, that appeared in Science Advances, looks at one of the most amazing things about their evolutionary history -- they were the only branch of the dinosaur clade that survived the cataclysmic mass extinction at the end of the Cretaceous Period.  What allowed birds to make it through the bottleneck that killed all of their near relatives -- and not only survive, but thrive and rediversify?

The evidence is that the extinction event selected for two things; small body size, and a shift toward young being altricial -- born relatively helpless and undeveloped, and therefore requiring more parental care.  Some lineages of birds would eventually increase in body size again, but they never again would reach the colossal proportions that their cousins did during the Jurassic and Cretaceous Periods.

"We have typically not looked at the change in DNA composition and model across the tree of life as a change that something interesting has happened at a particular point of time and place," said Stephen Smith, of the University of Michigan, who co-authored the study.  "This study illustrates that we have probably been missing something...  We found that adult body size and patterns of pre-hatching development are two important features of bird biology we can link to the genetic changes we’re detecting.  One of the most significant challenges in evolutionary biology and ornithology is teasing out the relationships between major bird groups — it’s difficult to determine the structure of the tree of life for living birds."

The study not only elucidated relationships between extant groups of birds, it allowed the researchers to pinpoint when groups diverged from each other, and therefore what innovations were likely to be connected with events occurring on the Earth at the time.

The second study, which appeared in Nature Ecology & Evolution, looked at the question I began with -- the impossibly bright colors that are characteristic of so many bird species.  Colors in birds arise two ways -- pigments (chemicals which absorb some frequencies of light and reflect others) and structural color (due to feathers creating a combination of refraction and interference; this is also known as iridescence).  Most pigmented color in birds is relatively drab -- blacks, grays, and various shades of brown -- the flashing blues, greens, and purples you see in groups like tanagers, hummingbirds, and sunbirds are almost entirely due to iridescence.

The researchers went through images of as many of the 9,409 species of birds currently in existence, along with the current best iteration of the family tree of birds, to try and figure out where along the way iridescence evolved, and how it spread so widely among this class of animals.  

And what they found was that 415 distantly-related branches of the tree have iridescent feathers, and the common ancestor of all modern birds -- something like eighty million years ago -- was very likely iridescent.

"I was very excited to learn that the ancestral state of all birds is iridescence," said Chad Eliason, of the Field Museum in Chicago, who was the paper's lead author.  "We've found fossil evidence of iridescent birds and other feathered dinosaurs before, by examining fossil feathers and the preserved pigment-producing structures in those feathers.  So we know that iridescent feathers existed back in the Cretaceous -- those fossils help support the idea from our model that the ancestor of all modern birds was iridescent too."

There are still a lot of questions left unanswered, however.  "We still don't know why iridescence evolved in the first place," Eliason said.  "Iridescent feathers can be used by birds to attract mates, but iridescence is related to other aspects of birds' lives too.  For instance, tree swallows change color when the humidity changes, so iridescence could be related to the environment, or it might be related to another physical property of feathers, like water resistance.  But knowing more about how there came to be so many iridescent birds in the tropics might help us understand why iridescence evolved."

Which is extremely cool.  Something to think about next time you see one of those brilliant little flying jewels flit by.  The stunning colors we appreciate every day on our bird feeders and in the wild have a very long history -- going back to a trait that evolved something like eighty million years ago.

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

Jaw dropping

One consistent misapprehension a lot of people have about evolution is that the process of natural selection always leads toward organisms becoming stronger, smarter, faster, and more complex.

As my evolutionary biology professor put it, this is incorrect because at its core, "evolution is the law of whatever works."  The most successful, widespread, diverse, and numerous animals on Earth are, by far, insects -- they're not necessarily any of the aforementioned things (especially smart), they are just exceedingly good at reproducing fast and filling available niches.  Whatever traits happen to be selected for by the environment at the time result in the direction evolution takes.  And this can change if the environment changes -- as has been observed in a number of fossil lineages where the average body size increased for a while, then reversed course and decreased.

Evolution is not goal-oriented.  The idea that it's heading in a particular pre-determined direction is a holdover from the old Aristotelian idea of the scala naturae, where there's a ladder of increasing complexity and intelligence, with humans, of course, occupying the top rung.  (At least until the concept was adopted by medieval Christian scholars; at that point humans got knocked down a couple of pegs, with the higher rungs taken up by angels and, at the top, God.)  But you still hear people -- even scientific, rational types -- talk about "primitive" and "advanced" species, and ones being "highly-evolved" (or not), when the truth is that all modern life forms, from bacteria to birch trees to baboons, have exactly the same length of evolutionary history, going back to LUCA (the "last universal common ancestor") something like four billion years ago.

It's just that in those four billion years, some of them have changed a great deal more than others have.

Given that even people who are quite knowledgeable often still have that bias floating around, it can come as a significant shock to find out that there are some anatomically simple animals that are actually quite recently evolved -- and close to other species we consider "advanced."  Two of the most striking examples are echinoderms (such as starfish and sea urchins, which undergo a peculiar decentralization during development, losing most of their sophisticated organs up to and including the central nervous system) and tunicates (sometimes referred to as "sea squirts," which superficially look like filter-feeding sponges but are actually some of the closest invertebrate relatives to vertebrates).  In both cases, the larvae give away their actual placement in the family tree of life, as does their DNA; both of these groups represent fairly recent developments, as these things go.

Another example, and the reason this topic comes up, is Class Agnatha, which includes lampreys and hagfish, and sometimes are called "jawless fish."  (The term "fish" actually has no evolutionary relevance; it lumps together very distantly-related groups, excluding others that are far closer cousins.  Lungfish and coelacanths, for example, are more closely related to amphibians -- and thus to us -- than they are to your standard-issue fish.)

European river lamprey (Lampetra fluviatilis) [Image licensed under the Creative Commons Tiit Hunt, Jõesilmud2, CC BY-SA 3.0]

In any case, lampreys and hagfish are distinguished on the gross anatomical level by lacking lower jaws, and -- by the typical way of thinking about this -- must be some kind of "primitive" holdover from before paired jaws were developed by the rest of us vertebrates.  It's true they branched off early, and are only distantly related to other vertebrates, but some research that came out last week in Nature Ecology & Evolution suggests that their lineage lost their lower jaws, not that our direct ancestors somehow gained them along the way.

The research looked at the genetic control over jaw development, and found that the pattern was strikingly similar between vertebrates with jaws and those without -- but that those without had switched off a gene called pou5 that guides cells in the neural crest, a cluster of cells in the head of the embryo that specialize to produce a number of different structures.  Lampreys and hagfish have the gene, they just don't express it in the embryonic tissue that in other vertebrates leads to the mandible -- suggesting strongly that they evolved from ancestors that had it and expressed it.

"While most of the genes controlling pluripotency are expressed in the lamprey neural crest, the expression of one of these key genes -- pou5 -- was lost from these cells," said Joshua York of Northwestern University, lead author of the paper.  "Amazingly, even though pou5 isn't expressed in a lamprey's neural crest, it could promote neural crest formation when we expressed it in frogs, suggesting this gene is part of an ancient pluripotency network that was present in our earliest vertebrate ancestors."

So this once again confounds our tendency to fit things into a scala naturae-like pattern.  Evolution can happen not only from gaining features, but from losing them.  In the case of lampreys and hagfish, a pretty important structure -- without which, nevertheless, they appear to do just fine.

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

Song of the Rifleman

As an avid birdwatcher, I've learned many of the vocalizations of our local species.  Some, especially the migratory species we only hear from May to September, I have to relearn every year, but a few of them are so distinct that my ears perk up whenever I hear them.  One of my favorites is the whirling, ethereal song of the Veery (Catharus fuscescens):

Another lovely one, often heard in the same sorts of deep-woods habitats as the Veery, is the Wood Thrush (Hylocichla mustelina):

By far the strangest bird songs I've ever heard, though, we came across when we visited the lowlands of eastern Ecuador about twenty years ago.  There were two we heard but never saw -- first, the aptly-named Screaming Piha (Lipaugus vociferans), which can be heard for miles:

And second, the Great Potoo (Nyctibius grandis), which is cryptically-colored and nocturnal, so they're almost never seen.  But when they sing at night... holy crap.  Imagine being out in the jungle, alone, at night, and hearing this:

It's no wonder the locals thought there were monsters out there.

Bird songs serve two main purposes.  They're territorial defense signals and mate attractants.  (Which led a former student of mine to say, in some astonishment, "So birds only sing when they're mad or horny?")  Songs are usually only done by males, and mostly during the breeding season.  Calls, on the other hand, are done by both males and females, at any time of the year, and can mean a variety of things from "there's food over here" to "watch out for the cat" to "hey, howsyamommaandem?"  (The latter mostly from birds in the southeastern United States.)  Those of you in the eastern half of North America certainly already have heard the difference; our local Black-capped Chickadee (Poecile atricapillus) has a call, the familiar "chicka-dee-dee-dee-dee" that gives the species its name, and a song -- a two-note whistle with the second note a whole step below the first.  Listening to them, you'd never guess it was the same bird.

There's an interesting distinction in how animals vocalize.  Some vocalizations seem to be innate and hard-wired; the barking of dogs, for example, doesn't need to be learned.  A great many bird species, however, including songbirds and parrots, learn vocalizations, and deprived of examples to learn from, never sing.  (This includes the amazing mimicry of birds like the Australian Superb Lyrebird (Menura novaehollandiae), which can learn to imitate not only birdsongs but a huge variety of other sounds as well):

The topic comes up because of a study that came out this week in the journal Communications Biology about the Rifleman (Acanthisitta chloris), a tiny species from New Zealand that is one of only two surviving species in the family Acanthisittidae, the New Zealand wrens, which are only distantly related to the more familiar and widespread true wrens.  (If you're curious, its odd common name comes from the cheerful colors of the plumage, which someone decided looked like a military uniform:

[Image licensed under the Creative Commons digitaltrails, Lake Sylvan - Rifleman (5626163357) (cropped), CC BY-SA 2.0]

The Rifleman is not a songbird, and (if the preceding distinction holds) should be unable to learn vocalizations; any sounds it makes should be instinctive and fixed, like the clucking of a chicken.  But the study found that there were variations in the vocalizations of different individuals, and those variations were independent of how closely related they were; what mattered was how nearby they lived to each other, implying that the alterations in sound were learned, not innate. 

"The vocal behavior that we were unravelling in this study is very similar to what is known as vocal accommodation in human linguistics," said Ines Moran, of the University of Auckland, who led the research.  "It's similar to our ability to adjust our ways of speaking in different social, dialectal, or hierarchical settings -- modulating our voices to better fit in certain social groups."

So bird vocalizations may not be as simple as we'd thought.  Like most things, I suppose.  It brings up the silly distinction that I heard over and over again from students, that there's a split between "human" and "animal."  We're clearly animals; and, conversely, what we call "animals" share a great deal more with us than we often realize.  We have a lot to learn from the other species we whom we cohabit the planet.  It's nice that we're beginning to pay more attention.

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

Species, types, and the "No True Scotsman" fallacy

One of the most frustrating of logical fallacies is the No True Scotsman fallacy.

It gets its name from an almost certainly apocryphal story, in which a serial rapist and killer is being pursued by the police in Glasgow, and a Scottish MP encourages the police to search amongst the immigrant population of the city.  "No Scotsman would do such a thing," the MP said.

When the criminal was caught, and turned out to be 100% Scottish, the MP was challenged about his remark.

"Well," he said, drawing himself up, "no true Scotsman would have done such a thing!"

The crux of this fallacy is that if you make a statement that turns out, in view of evidence, to be false, all you do is shift your ground -- redefine the terms so as to make your original point unassailable.

Very few other fallacies have such a capacity for making me want to smack my forehead into a wall as this one.  Someone who commits this fallacy can't be pinned down, can't be backed into a corner, can't receive his comeuppance from the most reasoned argument, the most solidly incontrovertible evidence.  The dancing skills of a master of the No True Scotsman fallacy are Dancing With The Stars quality.

All of this comes up because of an online discussion that I read, and (yes) participated in, a couple of days ago, on the topic of the demonstrability of evolution.  Someone, ostensibly a supporter of evolution but seemingly not terribly well-read on the subject, was using such evidence as the fossil record as a support for the idea.  A creationist responded, "The fossil record, and fossil dating, are inaccurate.  You evolutionists always think that bringing us a bunch of bones and shells proves your point, but it doesn't, because no one can really prove how old they were, and none of them show one species turning into another.  You can't show a single example, from the present, of one species becoming another, and yet you want us to believe in your discredited theory."

Of course, I couldn't let a comment like that just sit there, so I responded, "Well, actually, yes, I can.  I know about a dozen examples of speciation (one species becoming another) occurring within a human lifetime."

Challenged to produce examples, I gave a few, including the ones that I described in an earlier post (Grass, gulls, mosquitoes, and mice, February 9, 2012), and then sat back on my haunches with a satisfied snort, thinking, "Ha.  That sure showed him."

Well.  I should have known better.  His response, which I quote verbatim: "All you did was show that one grass can become another grass, or a mosquito can become another mosquito.  If you could show me a mosquito that turned into a bird, or something, I might believe you."

Now, hang on a moment, here.  You asked me for one thing -- to show one species turning into a different species, in the period of a few decades.  I did so, adhering to the canonical definition of the word species.  And now you're saying that wasn't what you wanted after all -- you want me to show one phylum turning into a different one, in one generation?

I sat there, sputtering and swearing, and not sure how to answer.  So I said something to the effect that he'd pulled a No True Scotsman on me, and had changed the terms of the question once he saw I could answer it, and he'd damned well better play fair.  He humphed back at me that we evolutionists couldn't really support our points, and we both left the discussion as I suspect most people leave discussions on the internet -- unconvinced and frustrated.  So I was pondering the whole thing, and after taking my blood pressure medications I had a sudden realization of where the confusion was coming from.  It was from the idea of a type of organism.

Most people who aren't educated in the biological sciences (and I'm not including just formal education, here; there are many people who have never taken a single biology class and know plenty about the subject) really don't understand the concept of species.  They think in types.  A bird is one type of thing; a bug is a different one.  If you pressed them, they might admit that there were a few types of birds that seemed inherently different.  You have your big birds (ostriches), your medium-sized birds (robins), and your little birds (hummingbirds).  I've had students that have thought this way, and when they hear I'm a birdwatcher, they seem incredulous that this could be a lifelong avocation.  Wouldn't I run out of new birds to see pretty quickly?  When I tell them that there are over 10,000 unique species of birds, they seem not so much awed as uncomprehending.

The phylogenetic tree of birds (Class Aves) [credit: Dr. Gavin Thomas, University of Sheffield, UK]

I suspect that the source of this misapprehension is the same as the source of the general misapprehension regarding the antiquity of the Earth and the origins of life: the Bible.  In Leviticus 11, where they go through the whole unclean-foods thing that eventually would be codified as the Kosher Law, they split up the natural world in only the broadest-brush terms; you have your animals that have hooves and chew the cud, various combinations of ones that don't, creatures that have fins and scales and ones that don't, insects that jump and ones that don't, and a few different classes of birds (which, to my eternal amusement, includes bats).  And that's pretty much it.  Plants were sorted out into ones that had edible parts (wheat, figs, olives), ones that had useful wood (boxwood, cedar, acacia), and ones that had neither of the above (thorn bushes).  And these distinctions worked perfectly well for a Bronze-Age society.  It kept you from eating stuff that was bad for you, told you what you could build stuff from, and so on.  But as a scientific concept, the idea of "types of living things" kind of sucks.  And yet it still seems to live on in people's minds, lo unto this very day.

So, anyway, that was my brief excursion into that least useful of endeavors, the Online Argument.  It gave me a nice example of the No True Scotsman fallacy to write about here.  And it really didn't affect my blood pressure all that much, but it did make me roll my eyes.  Which seems to happen frequently when I get into conversations with creationists.

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

Myth come to life

While I've been known to make fun of the cryptid hunters, there's something to be said for their persistence.

Not only do we have people working hard to prove the continued existence of animals thought by science to be extinct -- most notably, the thylacine (Thylacinus cynocephalus) of southern Australia, which actually has a Facebook page devoted to sightings -- there are the devotees of animals science has never admitted in the first place, like Bigfoot, Nessie, and dozens of lesser-known denizens of myth and legend.

Despite my skepticism, no one would be more delighted than me if one of these elusive beasties turned out to be real.  Which is why I was so tickled when a friend and loyal reader of Skeptophilia sent me a link about a cryptid I'd never heard of -- the Corsican cat-fox -- which was just proven to be very real indeed.

The legend has been around for centuries; a wildcat in Corsica that is larger than your typical house cat, has rusty brown fur, and a long, ringed tail, notorious for raiding chicken coops.  Called in the Corsican language ghjattu-volpe -- "cat-fox" -- it was thought to be a myth.

It's not.  In an intensive effort to establish the legend's veracity, the ghjattu-volpe was found -- not only photographed, but captured for DNA sampling.

Genetic analysis has shown that its DNA is distinct from domestic cats, from wildcats in mainland Europe, and wildcats in the neighboring island of Sardinia.  

The fact that this animal stayed undetected for so long has left the locals saying "see, we told you so," and encouraged the absolute hell out of the proponents of other elusive animal claims.  Even so, I think some cryptids are unlikely in the extreme -- the Loch Ness Monster topping that list.  The idea that there is a breeding population of plesiosaurs in Loch Ness, which somehow survived the last ice age (during which that region of Scotland was under a thirty-meter-thick sheet of ice) and has gone undetected despite years of searching with sonar and other high-tech telemetry devices, strikes me as a little ridiculous.

However, I don't find anything inherently implausible about there being a large, elusive proto-hominid in the Pacific Northwest.  I lived in Seattle for ten years and spent my summers camping in the Cascades and Olympics, and man, that is some trackless wilderness up there.  Neither do I doubt the possibility of the survival of thylacines, ivory-billed woodpeckers, and various other thought-to-be-extinct species.

But "possible" and "not inherently implausible" doesn't equal "real."  I remain very much a "show me the money" type.  And that means more than just blurred photos and videos.  (To borrow a phrase from Neil deGrasse Tyson, Photoshop probably has an "add Bigfoot" button.)  Until there's hard evidence, I'm not going to be in the True Believer column.

Even so, I have to admit that the Corsican cat-fox certainly is encouraging to those of us who want to believe.

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