Animalia paradoxa

Carl Linnaeus was born in Råshult, Sweden, on 23 May 1707.  His father Nils was the minister of the parish of Stenbrohult but was also an avid gardener, and the story goes that when Carl was young and got upset, Nils would bring him a flower and tell the little boy its name, and that always calmed him down.

The love of botany -- and of knowing the names of living things -- was to shape Carl Linnaeus's life.  Prior to his time, there was no systematic way of giving names to species; there were dozens of names in various languages for the same species, and sometimes several different names in the same language.  Additionally, the fact that this is before the recognition of the relatedness of all life meant that things were named simply by their superficial appearance, which may or may not indicate an underlying relationship.  We still have some leftovers from this haphazard practice, such as the various birds called buntings (from the Middle English buntynge, "small bird") that aren't necessarily related to each other.  (For example, the North American indigo bunting is in the cardinal family; the European pine bunting in the family Emberizidae.) 

Young Linnaeus was lucky enough not only to have supportive parents, but a variety of people who recognized his intellect and ability and nurtured him in his studies.  (Amongst them was the scientist and polymath Olof Celsius, whose nephew Anders gave us the Celsius temperature scale.)  He was primarily interested in botany, but quickly became frustrated with the fact that the same plant could have six different names in six different villages -- and worse still, it was impossible to communicate taxonomic information clearly to botanists in other countries, where the names would have come from their native language.

So he decided to do something about it.

Linnaeus came up with the idea of binomial nomenclature -- the "two-name naming system," more commonly called "scientific names."  Each species would be assigned a unique and unambiguous name made of the genus and species names, each derived from Latin or Greek (which were the common languages of science at the time).  The genus would include various related species.  His determinations of who was related to whom were based upon appearance -- this is long before genetics became the sine qua non of systematics -- and some of Linnaeus's classifications have been revised in the 250-odd years since he wrote his magnum opus, the Systema Naturae.  But even so, the system he created is the one we still use today.

And this is why scientists the world over will know, if you say Mustela nigripes, that you are talking about the black-footed ferret.  (The scientific name translates to... "black-footed ferret."  Just because they're fancy-sounding Latin and Greek words doesn't mean they're all that revelatory.)

So Linnaeus took the first steps toward ordering the natural world.  But what is less well-known is that he included a few animals in his book that are more than a little suspect -- and labeled them as such, illustrating an admirable dedication to honoring hard evidence as the touchstone for scientific understanding.

In a section called "Animalia paradoxa," Linnaeus listed some "species" that had been reported by others, but for which there was no clear evidence.  From the tone of his writing, it's obvious he was doubtful they existed at all, and was only including them to point out that any reports of them were based upon hearsay.  These included the following genera, along with his description of them:

• Hydra: "body of a snake, with two feet, seven necks and the same number of heads, lacking wings, preserved in Hamburg, similar to the description of the Hydra of the Apocalypse of St.John chapters 12 and 13.  And it is provided by very many as a true species of animal, but falsely.  Nature for itself and always the similar, never naturally makes multiple heads on one body.  Fraud and artifice, as we ourselves saw [on it] teeth of a weasel, different from teeth of an Amphibian [or reptile], easily detected."
• Monoceros: "Monoceros of the older [generations], body of a horse, feet of a 'wild animal,' horn straight, long, spirally twisted.  It is a figment of painters.  The Monodon of Artedi [= narwhal] has the same manner of horn, but the other parts of its body are very different."
• Satyrus: "Has a tail, hairy, bearded, with a manlike body, gesticulating much, very fallacious, is a species of monkey, if ever one has been seen."
• Borometz: "The Borometz or Scythian Lamb is reckoned with plants, and is similar to a lamb; whose stalk coming out of the ground enters an umbilicus; and the same is said to be provided with blood from by chance devouring wild animals.  But it is put together artificially from roots of American ferns. But naturally it is an allegorical description of an embryo of a sheep, as has all attributed data."
• Manticora: "Has the face of a decrepit old man, body of a lion, tail starred with sharp points."

A manticore, from Johannes Jonston's Historiae Naturalis (1650) [Image is in the Public Domain]

I've always admired Linnaeus -- like him, I've been fascinated with the names of things since I was little, and started out with plants -- but knowing about his commitment to avoid getting drawn into the superstition and credulity of his time makes me even more fond of him.  He was unafraid to call out the Animalia paradoxa as probable hoaxes, and that determination to follow the rules of scientific skepticism still guides taxonomists to this day.

Of course, sometimes there are some bizarre "forms most beautiful and most wonderful" in the natural world, to borrow a phrase from Darwin.  When the first taxidermied pelts and skeletons of the duck-billed platypus were sent from Australia back to England, many English scientists thought they were a prank -- that someone had stitched together the remains of various animals in an attempt to play a joke.  And once convinced that they were real, the first scientific name given to the platypus was...

... Ornithorhynchus ("bird-billed") paradoxa.

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Birds of a feather

The word species has got to be the mushiest term in all of science.

It's one of those situations where you think you know what something means until you start pushing on it.  When humans started to put a serious effort into categorizing other life forms -- Aristotle is usually credited with being the first to do this in a systematic way -- it seemed obvious enough.  Members of a species are similar morphologically.  Put more simply, you can tell a cat from a dog because they look different.

The problem is, this starts to cause problems just about immediately.  What about organisms that look very different, but we still consider to be the same species?  Dogs, in fact, are a good example.  Imagine you're an alien scientist arriving on Earth, and you're looking at a St. Bernard and a chihuahua.  If a human said, "These are the same species," my guess is you'd do whatever passes for laughter on your home world, then get back in your spaceship and fly away after writing "No intelligent life" on the map of the Solar System.

Dogs, of course, aren't the only ones; there are lots of examples in nature of different-looking organisms that are considered conspecific.  So in the 1800s, the definition was revised to, "a group of organisms that are capable of mating and producing offspring."  This worked until people started to think about mules, which are the offspring of a horse and a donkey (usually considered separate species).  Then, it was pointed out that although alive and well, (most) mules are infertile, so a word was added to take care of that problem: "a group of organisms that are capable of mating and producing fertile offspring."

It only got worse from here.  An awkward difficulty with the above definition is, what about asexual species?  They kind of don't fit in no matter how you look at it.  Oh, well, maybe they get their own version of the definition.  But what about ring species?  This is a group of populations, often arranged in a ring around a geographical barrier (thus the name) where all of them can interbreed except for the ones at the "ends" of the ring  It's been observed multiple times, including a group of salamanders in California, the Greenish Warbler of central Asia, and a ring of gull species -- the latter of which goes all the way around the world.

So do these represent one species, or many?  Within the ring, some of them are interfertile, and others aren't.  And splitting the ring doesn't help; then you're separating populations that are interfertile.  In fact, like asexual species, ring species seem to be unclassifiable with the canonical definition.

It all comes, my evolutionary biology professor said to us, from the desperation humans have to pigeonhole everything.  "The only reason we came up with the concept of a species in the first place," he said, "is because humans have no near relatives."

Of course, none of this sits well with the creationists, because a central tenet of their beliefs is that each kind of life form was created by God as-is and nothing's changed since.  Which is all well and good until you ask, "What do you mean by 'kind of life form'?"  They respond that God created "discrete forms with genetic boundaries to interbreeding," which they call baramins (a neologism coined from the Hebrew words for "created" and "kind").  So the ring species of gulls isn't a problem because gulls are a "kind."  In fact, you can define "kind" in this context as "a classification of life forms that conveniently makes all of the internal contradictions go away.  Now stop asking questions."  

In any case, there really is no good, consistent definition of species that covers all the exceptions.  Even now that we have genetic analysis -- which is currently the touchstone for classification -- it only further reinforces the fact that evolution generates a continuum of forms, and you're asking for trouble if you try to subdivide them.  Only in cases like ourselves, where there are no living near relatives, does it seem clear-cut.

Take the study out of the University of Colorado that appeared in Nature Communications this week.  It's about a trio of species of birds, so being a rather fanatical birder, it immediately caught my eye.  The species involved (and I use that term guardedly, for reasons that will become obvious) are the Common Redpoll, (Acanthis flammea) the Hoary Redpoll (Acanthis hornemanni), and the Lesser Redpoll (Acanthis cabaret), all types of finch with a characteristic red splotch on the forehead.  

Common Redpoll (Acanthis flammea) [Image licensed under the Creative Commons Cephas, Carduelis flammea CT6, CC BY-SA 3.0]

The Lesser Redpoll is only found in Europe, but the other two occur in North America.  They have pretty obvious color differences; the Lesser Redpoll is brownish, the Hoary Redpoll is almost white, and the Common Redpoll is somewhere in the middle, with reddish flanks.  The size differs, as well, with the Lesser at the small end and the Hoary at the large end.

Lesser Redpoll (Acanthis cabaret) [Image licensed under the Creative Commons Carduelis_cabaret.jpg: Lawrie Phipps derivative work: MPF (talk), Carduelis cabaret1, CC BY 2.0]

However, the differences aren't huge.  We get Common Redpolls at our bird feeders in winter fairly regularly, but Hoary Redpolls are a rare sighting in our area.  Every winter I scan the flocks of redpolls looking for whiter individuals, but I still have never seen one.  However, I may be able to cross that one off the list of "species I haven't seen" -- because the current study has shown that despite the differences in appearance, all three are a single species.

Hoary Redpoll (Acanthis hornemanni) [Image licensed under the Creative Commons Ron Knight from Seaford, East Sussex, United Kingdom, Arctic Redpoll (Acanthis hornemanni) (13667519855), CC BY 2.0]

The color and size differences, the researchers found, are due to a "supergene complex" -- a single cluster of genes that work together to produce a specific phenotype.  What's striking is that despite the differences in that gene complex between the three different groups of redpolls, they are otherwise about as genetically identical as it's possible to get.  And... they're all potentially interfertile.

"Often times we assume that a lot of traits can act independently, meaning that different traits can be inherited separately from one another, but this particular result shows that sometimes these traits are actually tightly linked together," said Erik Funk, lead author on the paper, in an interview in Science Daily.  "At least for these birds, they're inheriting a whole group of traits together as one."

Birders tend to hate it when confronted with "lumpers," as they call researchers who merge species together, therefore reducing the number of potential birds to chase after.  They much prefer "splitters," who take previously single species and subdivide them, like another "winter finch," the Red Crossbill (Loxia curvirostra), which according to some taxonomists isn't a single species but several -- possibly as many as seven.  In any case, my point here is that this kind of thing happens all the time.  Like I said at the beginning, we think we have a clear idea of what's meant by a species until we start examining it.

But to me, this only increases my fascination with the natural world.  It's a beautiful, subtle, and complex interlocking web of organisms, and maybe the most surprising thing of all is that we do think it should be simple and easily classifiable.  As usual, our scheme for understanding the world turns out to be woefully inadequate -- and once again, science has come to the rescue by turning a lens on a small and unassuming bird as a way of pointing out how much more we have to learn.

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As I've mentioned before, I love a good mystery, which is why I'm drawn to periods of history where the records are skimpy and our certainty about what actually happened is tentative at best.  Of course, the most obvious example of this is our prehistory; prior to the spread of written language, something like five thousand years ago, most of what we have to go by is fossils and the remnants of human settlements.

Still, we can make some fascinating inferences about our distant ancestors.  In Lost Civilizations of the Stone Age, by Richard Rudgely, we find out about some of the more controversial ones -- that there are still traces in modern languages of the original language spoken by the earliest humans (Rudgely calls it "proto-Nostratic"), that the advent of farming and domestication of livestock actually had the effect of shortening our average healthy life span, and that the Stone Age civilizations were far more advanced than our image of "Cave Men" suggests, and had a sophisticated ability to make art, understand science, and treat illness.

None of this relies on any wild imaginings of the sort that are the specialty of Erich von Däniken, Zecharia Sitchin, and Giorgio Tsoukalos; and Rudgely is up front with what is speculative at this point, and what is still flat-out unknown.  His writing is based in archaeological hard evidence, and his conclusions about Paleolithic society are downright fascinating.

If you're curious about what it was like in our distant past, check out Lost Civilizations of the Stone Age!

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

The evolution of Little Red Riding Hood

Every once in a while, I'll run across a piece of scientific research that is so creative and clever that it just warms my heart, and I felt this way yesterday when I stumbled onto a link to the article in PLoS ONE called "The Phylogeny of Little Red Riding Hood," by Jamshid Tehrani of the University of Bristol.

The reason I was delighted by Tehrani's paper is that it combines two subjects I love -- evolutionary biology and mythology and folklore.  The gist of what Tehrani did is to use a technique most commonly used to assemble species into "star diagrams" -- cladistic bootstrap analysis -- to analyze worldwide versions of the "Little Red Riding Hood" story to see to what degree a version in (for example) Senegal was related to one in Germany.

Cladistic bootstrap analysis generates something called a "star diagram" -- not, generally, a pedigree or family tree, because we don't know the exact identity of the common ancestor to all of the members of the tree, all we can tell is how closely related current individuals are.  Think, for example, of what it would look like if you assembled the living members of your family group this way -- you'd see clusters of close relatives linked together (you, your siblings, and your first cousins, for example) -- and further away would be other clusters, made up of more distant relatives grouped with their near family members.

So Tehrani did this with the "Little Red Riding Hood" story, by looking at the similarities and differences, from subtle to major, between the way the tale is told in different locations.  Apparently there are versions of it all over the world -- not only the Grimm Brothers Fairy Tales variety (the one I know the best), but from Africa, the Middle East, India, China, Korea, and Japan.  Oral transmission of stories is much like biological evolution; there are mutations (people change the story by misremembering it, dropping some pieces, embellishment, and so on) and there is selection (the best versions, told by the best storytellers, are more likely to be passed on).  And thus, the whole thing unfolds like an evolutionary lineage.

In Tehrani's analysis, he found three big branches -- the African branch (where the story is usually called "The Wolf and the Kids"), the East Asian branch ("Tiger Grandmother"), and the European/Middle Eastern Branch ("Little Red Riding Hood," "Catterinella," and "The Story of Grandmother").  (For the main differences in the different branches, which are fascinating but too long to be quoted here in full, check out the link to Tehrani's paper.)

Put all together, Tehrani came up with the following cladogram:

WK = "The Wolf and the Kids," TG = "Tiger Grandmother," "Catt" = "Catterinella," GM = "The Story of Grandmother," and RH = "Little Red Riding Hood;" the others are less common variations that Tehrani was able to place on his star diagram.

The whole thing just makes me very, very happy, and leaves me smiling with my big, sharp, wolflike teeth.

Pure research has been criticized by some as being pointless, and this is a stance that I absolutely abhor.  There is a completely practical reason to support, fund, and otherwise encourage pure research -- and that is, we have no idea yet what application some technique or discovery might have in the future.  A great deal of highly useful, human-centered science has been uncovered by scientists playing around in their labs with no other immediate goal than to study some small bit of the universe.  Further, the mere application of raw creativity to a problem -- using the tools of cladistics, say, to analyze a folk tale -- can act as an impetus to other minds, elsewhere, encouraging them to approach the problems we face in novel ways.

But I think it's more than that.  The fundamental truth here is that human mind needs to be exercised.  The "what good is it?" attitude is not only anti-science, it is anti-intellectual.  It devalues inquiry, curiosity, and creativity.  It asks the question "how does this benefit humanity?" in such a way as to imply that the sheer joy of comprehending deeply the world around us is not a benefit in and of itself.

It may be that Tehrani's jewel of a paper will have no lasting impact on humanity as a whole.  I'm perfectly okay with that, and I suspect Tehrani would be, as well.  We need to make our brains buckle down to the "important stuff," yes; but we also need to let them out to play sometimes, a lesson that the men and women currently overseeing our educational system need to learn.  In a quote that seems unusually apt, considering the subject of Tehrani's research, Albert Einstein said: "I am enough of an artist to draw freely upon my imagination. Imagination is more important than knowledge.  Knowledge is limited.  Imagination encircles the world."