taxonomy in public media

[Thomas G. Lammers]

At 10:56 PM 01-15-97 EST, Kyle Williams wrote:

>As mentioned in an earlier post the "official" explanation for the
>morphological similarities between the alien races (as well as their
>ability to interbreed) is that an ancient race populated numerous planets
>with their DNA.  By using this explanation the writers have made the
>humanoid races of the galaxy a monophyletic group which would allow for
>the (small) possibility of hybrid offspring to be created.  Of course its
>a cheesy excuse but at least its slightly better than having us believe
>that this is a case of extreme evolutionary convergence which occurred
>independently on hundreds of worlds.

At the risk of exerting too much effort on a seemingly inane topic (I do so
only because these kinds of things are often the only way to interest
students in biological concepts), I would just reiterate my original point
about cladograms. On this planet, the particular terminal taxon of interest
(Homo sapiens) ties in clearly to a phylogenetic tree that runs
ininterrupted right down through the phyla.  There is no evidence that H.
sapiens is (to use weed science parlance) adventive, introduced, or
naturalized on this planet. If we were, we'd all be sitting around,
scratching our heads, and wondering what our sister-group is, instead of
universally pointing at the apes and shouting "Cousin!"   We are far to
closely related to extant apes to adopt the view that we "came from the
stars".  I assume the same cladistic relationships hold true for sentient
species on other worlds.  Every world with an indigenous autochthonous biota
will have its oyn Master Cladogram, totally detached from all others.
Adventive species (humans colonizing a terraformed Mars, for example) will
stick out like a sore thumb.  Alternatively, if we accept some sort of Fred
Hoyle pangenesis, with the initial living unicells spreading among the
planets like drift seeds, giving rise to life wherever they "come ashore",
we are still left with a LOT of divergence separating the sentient terminal
taxa.  Draw yourself a cladogram!  Homo sapiens is still more closely
related cladistically to Nitella and Cladophora that to Mr. Spock and Darth
Vader.  Ergo, no human-alien hybridization is possible.

**************************************************************************
Thomas G. Lammers
Department of Botany                     Classification, Nomenclature,
Field Museum of Natural History          Phylogeny and Biogeography
Roosevelt Road at Lake Shore Drive       of the Campanulaceae
Chicago, Illinois 60605-2496 USA

e-mail:     lammers at fmppr.fmnh.org
voice mail: 312-922-9410 ext. 317
fax:        312-427-2530

"This whole genus [Lobelia] would richly reward any botanist for an
analytical investigation."  -- John Lindley (1826).