Linnaean Categories

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Science  20 Dec 1996:
Vol. 274, Issue 5295, pp. 1993-1997
DOI: 10.1126/science.274.5295.1993a

Solomon W. Golomb (Letters, 8 Nov., p. 902) suggests introducing the rank of “empire” to denote the highest division(s) of the living beings. I hope that any sympathetic attitude toward this proposal will be checked against the following considerations:

  1. 1) Carl Woese's divisions of life on Earth are not “categories.” Bacteria, Archaea, and Eukarya are “‘taxa,” as are Aves (the birds), Coleoptera (the beetles), or Homo sapiens. Categories are those things (for example, the species, the genus, the phylum) to which Golomb would like to add another term (the empire).

  2. 2) These Linnaean categories, in spite of their long traditional use, are not unquestionable. An increasing number of students are arguing for abolishing them as arbitrary and, in one opinion, even nonsensical and overtly misleading (1). These matters are admittedly controversial, but this does not seem the best time for introducing new formal ranks.

  3. 3) The threefold basal split of living beings that seems to be “gaining acceptance” so as to require introducing this highest rank of “empire” has two obvious weaknesses: (i) it corresponds to an incompletely resolved phylogeny, and (ii) it takes for granted the monophyletyic character of each and all of the three taxa, that could be true (as assumed in the archea theory) but might not be so (as assumed by the eocyte theory).

  4. 4) The term “imperium” is all but new. Linnaeus (2) used the term “Imperium Naturae” as the whole embracing his three kingdoms (animals, plants, minerals), and the same term has been recently revived, more or less intentionally, by a few modern authors (3).

References and Notes

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