Tuesday, 6 April 2010

Awareness in Classification 2

In response to Michael from last 'Awareness in Classification' post

Several relationships are proposed, some conflict with others:
    1. Bird - dinosaur
    2. Humans - Apes
or:
    3. Bird - non-avian dinosaur
    4. Human - non-human ape
In examples 1 and 2 above dinosaur implies some distinct group of animals, as does apes. In examples 3 and 4 above 'non-avian' stands for 'not-bird', and 'non-human' stand for 'not human'. Thus,
    5. Bird - not bird
    6. Human - not human
It is tempting to explore the idea of what a 'not bird' might be (resisting exploring what a 'not-human' might be): a flower, a rabbit, a house...

Another relationship might be:
    7. Vertebrate-invertebrate
or
    8. Vertebrate-not vertebrate
It is tempting to explore the idea of what a 'not vertebrate' might be: a flower, a rabbit, a house...

One might argue that context is all important. Of course, a 'not vertebrate' doesn't mean a flower. Well, once again, what does it mean? 'Not vertebrates' are paraphyletic. One might re-classify all 'not vertebrates' as vertebrates, thus making 'not vertebrates' monophyletic (One might re-classify birds as dinosaurs making them monophyletic). Does this mean, now, that birds are invertebrates? Prokaryotes are paraphyletic. One might re-classify all 'prokaryotes' as eukaryotes, thus making 'prokaryotes' monophyletic. Does this mean, now, that birds are prokaryotes?

Words do indeed have multiple meanings. A taxon name is best associated with a relationship. Then the meaning can be empirically explored.