Real species

Bob Mesibov mesibov at SOUTHCOM.COM.AU
Sat Apr 17 16:47:49 CDT 2004

Richard Pyle wrote:

"An alternative view would represent the world of living things as one great
big spectrum of progressively darker shades of grey, starting with the white
end representing the two most distantly-related organisms on the planet, and
continuing to the black end representing any given pair of identical twins
or clones.  The metric for the level of grey can be something like time
since most recent common ancestor, or overall genetic divergence, or
probability that future generations of descendents will exchange genes --
whatever (that's a whole 'nother debate).

Obviously, the spectrum of grey is not perfectly smooth (i.e., the most
distantly-related living humans are a LOT closer to each other, than either
is to any given Pan or Pongo), and it is this sort of sharp discontinuity
among the extant global biome that makes it easy to think of species as
"real". But just as there are cases of extant populations that fall into
your "fuzzy" grey zone between the black and white zones, every organism
unambiguously within the white (heterospecific) zone is the descendant of a
lineage of information-flow that began in the black (conspecific) zone and
passed through the grey zone.  Thus, when you view the spectrum across time,
even the things that seem black and white disjunct today are following a
path of continuous blend from black to ever paler shades."

Very nice way to color in the instantaneous cross-section of a flow! And it
avoids entirely the 'species question'. It's therefore a great way to think about
Life and its history, but not a useful way to think if you're keen on classifying
things. Getting back to your original question about the reality of 'species', are
you happy to think about Life in a dynamic, non-'species' way for some
purposes, and in a static, 'species' way for others?
Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
Home address: PO Box 101, Penguin, Tasmania, Australia 7316
Home phone: (03) 6437 1195

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