Friday, December 20, 2013

What Do Neon Slugs Tell Us About Bigfoot?

Nothing, really.  How could any reasonable person expect them to?

Some fans of cryptozoology, though, think otherwise.

Mount Kaputar in Australia is apparently a kind of snail paradise, serving as home to a number of rare species of snails and slugs with little predation from vertebrates.  New Guinea may have its birds of paradise, but Mount Kaputar has the slugs of paradise -- large, hot pink slugs.  (Sexual selection drives the colors, patterns, and displays of the birds of paradise, but the reason for the hot pink color is not yet known.)  Until recently, these were thought to be just a variant of the red triangle slug, but careful morphological and genetic studies now indicate that these slugs should be grouped under a new species name.

Although this has nothing obvious to do with cryptozoology, it was reported on cryptozoology web sites (to which I will not here link), usually with the "therefore ..." unstated -- until, predictably, one of the regulars filled in what the take-home message was supposed to be:
You can have something like that crawling around, suddenly Bigfoot ain’t so farfetched, eh?
A statement like that isn't just pseudoscientific; it's pseudorational.  It's pseudoscientific because it seems intended to be the same kind of statement as when biologists say that, based on what we have discovered so far, probably around 90% of all species remain undescribed, whereas in fact, the writer's confidence that Bigfoot is a real, corporeal animal has no relationship whatsoever to science.

First a caveat regarding the word "species".  Sadly, determining what constitutes a species is not at all as straightforward as it seemed in my elementary school textbooks.  Those books said that two animals are of different species if they cannot produce offspring with each other or if, as with a horse and donkey producing a mule, the offspring is always infertile.  That is not really something that paleontologists can usually confirm or deny, though, so they have tended to create new species names whenever the differences seemed large enough to justify it -- in the process creating far too many species names, since sometimes two pieces of animals (for example, heads and legs) would be found separately and assigned different species, or juveniles would be mistaken to be different species than the adults, or the differences between males and females would be mistaken for the differences between different species.  Even when genetic information is available, though, the meaning of "species" has changed, as is clear when we are told that most of us are hybrids of two or three "species" of humans -- Homo sapiens, Neanderthals, and for many, the Denisovans.  (Even this is messed up, since according to taxonomic convention, Carl Linnaeus is the "type specimen" of Homo sapiens, meaning the species is defined by him.  Because he was a European, though, he must have had some Neanderthal ancestry, if the genetics studies are correct.)  In many cases, species boundaries are fuzzy, indistinct, and ultimately dependent on the varying criteria used to set them.
What can we infer from the discovery that the bright pink slugs of Mount Kaputar are a different species?  Extrapolations can be constructed on the basis of a "sample space".  A sample space has to be a collection of genuine possibilities, of which the observed cases can be said to be a typical sample.  For example, the trans-Neptunian object Sedna is near the limits of modern telescopes even when it is closest to the sun (at about 76 times the earth-sun distance), but it follows a very eccentric orbit.  Kepler's 2nd Law insures that Sedna is most often near its farthest point from the sun -- 937 times as far away as earth is.  Our sample space would consist of all possible numbers (consistent with current observations, that is) of Sedna-like objects at random locations on their orbits.  If Sedna is unique, we have been remarkably lucky to catch it in the brief period it is close enough to the sun for us to see.  It is much more likely that there are dozens, maybe even hundreds, of Sedna-like objects orbiting the sun.

What would be a corresponding sample space for these slugs?  As with the case of Sedna, it would have to be built of a population of possibilities that are related to the discovery about the slugs, so how would the discovery be described?
  • The existence of the pink slugs had been known already; in that sense they were not a new discovery at all.  
  • They are obviously somewhat different in appearance than red triangle slugs, but not so different in coloration or size to be obviously a different species.   
  • It could not have been "ethno-known" that they are a different species from red triangle slugs, since "species", with all its caveats and technicalities, does not entirely correspond to any concept outside modern biology.
  • The slugs are restricted to a remote, relatively inaccessible, and geographically limited range.
  • This was an evolutionary, not a revolutionary, change for science.  That's not an insult -- almost all science is that way -- but it serves to put the discovery into context.
Reasonable inferences, then, would include the following.
  • Genetic studies will show that other isolated populations of invertebrates with no visible differences are in fact different species.  (This happens all the time.)
  • Genetic studies will show that other isolated populations of land animals with no visible differences are in fact different species.  (Again, this is common.  It happened just recently with crocodiles, even though their populations do not appear to be as completely isolated.)
Every time the sample space is expanded, though, the inferences become less useful.  We're approaching the season of predictions for 2014, so we can take an example from the kinds of predictions psychics make. 

  • An actor who played a central character in MASH will die in 2014.  This has a very small "sample space", making it an interesting prediction.  It might well come true, but probably has no more than a 10% chance of coming true at random.
  • An actor who played a character on at least one episode of MASH will die in 2014.  This includes many more actors, so it is easier for this to come true. However, the implications of this for Alan Alda aren't quite so scary.
  • An actor who played a character on TV during the 1970's or 1980's will die.  It would be something like a miracle if this did not happen.  It's a prediction so safe as to be utterly useless.

Now let's look at the characteristics of a discovery of Bigfoot.
  • The mere existence of Bigfoot is not recognized by science at all.
  • Anything that could be called a "Bigfoot" would be obviously different from any animal known to have ever existed.  It would be larger and heavier than known human relatives like Paranthropus, and with different feet.  No other ape is known to be fully bipedal, including Gigantopithecus.
  • It is claimed that Bigfoot is ethno-known, on the basis of both modern alleged sightings and American Indian folklore.
  • Alleged Bigfoot sightings come from every U.S. state other than Hawaii and several of the Canadian provinces.  Depending on whether cryptids like the Almas, Yeti, and Yowie are considered the same thing as Bigfoot, this range might be extended to cover much of the world.
  • The verified discovery of a real Bigfoot would be a revolutionary discovery for (at least) primatology, evolutionary biology, and anthropology.  It would easily be worth a Nobel Prize.
In order to expand the sample space to include the discovery of Bigfoot, the sample space would have to include the addition of a new species of any land animal, important or unimportant, known or unknown, obviously different of visually indistinguishable, with a range of any size whatsoever.  With a sample space that big, only thing that can be said is that new species of animals remain unnamed, a fact as indisputable as that someone who has appeared on TV will die in the next 12 months.  The implications of this for the existence of Bigfoot, though, are even less than the implications of "an actor will die" for Alan Alda.

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