Human beings love to classify things.  We pigeonhole items into bins of our own making, for whatever the reason, to give us a feeling of having things organized and understood.   Do our pigeonholes reflect categories that are “out there” in nature, or are they constructs of our own minds?  Science reporters are announcing in bold print that there are “8.7 million species on Earth,” but a look at the fine print shows the error bars to be so enormous, there is more error than data.  What does this imply about the scientific validity of human classification schemes?

PhysOrg announced the 8.7 million number in its summary of a paper on PLoS Biology.1 National Geographic News followed up with a headline on one of the findings by Mora et al.: “86 Percent of Earth’s Species Still Unknown?”  Right off the bat, questions arise about how anyone can know the 8.7 million number with only 14 percent data. It would seem that many among the to-be-discovered organisms in the 86 percent bin might not be species at all, but members of smaller groupings like subspecies or varieties – or even of larger taxa [biological categories] like families or phyla.  In the 08/20/11 story, for instance, a whole new family, genus, and species was created for Protoanguilla palau, an eel that was classified as the only member of its new taxon.  Not all taxa are created equal.  Some phyla like Micrognathozoa and Ciliophora have only one member (SFSU.edu) while some lower taxa, like the order Coleoptera (beetles) within the class Insecta have over 2 million species.

Other scientific classification schemes seem to carve nature at its joints more cleanly.  The periodic table in chemistry is a classic example.  Even there, though, the use of atomic number to distinguish groups of things can seem a bit arbitrary in some situations, because there are isotopes of some elements that are heavier than elements with a higher atomic number.

Planet classification continues to vex astronomers ever since Pluto got demoted from a “planet” to a “dwarf planet” (after some tried minor planet or plutoid).  The International Astronomical Union (IAU) is the panel that places a kind of scientific imprimatur on nomenclature.  Back in 2006, after much debate, they voted Pluto out of the “Planet” bin. National Geographic News reported this week, though, that “New Finds Drive Debate” about whether Pluto should be promoted back to planet.  Those finds include other bodies large and small in the outer solar system (some larger than Pluto), new computer models that show objects moving around over time (moving, for instance from planetary satellite to sun-orbiter), exoplanets, and some planet-size bodies that don’t orbit stars at all….

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