Such expressions as that famous one of Linnæus, and which we often meet with in a more or less concealed form, that the characters do not make the genus, but that the genus gives the characters, seem to imply that something more is included in our classification, than mere resemblance. I believe that something more is included; and that propinquity of descent,—the only known cause of the similarity of organic beings,—is the bond, hidden as it is by various degrees of modification, which is partially revealed to us by our classifications (Darwin, 1859, p. 413f).

Monday, 31 March 2008

Didn't we discuss this before?

I once walked into my colleague's room and pointed out that his sink was leaking and getting some boxes full of reprints wet. I suggested he should get it fixed or move the boxes. We discussed it a little and after a short while it was forgotten. A year later I noticed that the problem had not been fixed. The reprints were all moldy and the leak had spread staining his carpet. I pointed it out to him again. He simply dismissed it with the line "Didn't we discuss this before?"

That same line is used throughout systematics and biogeography to dismiss lengthy heated debates that never were resolved. Who, for instance, were the victors in the following debates?

  • Cladistics versus Phenetics

  • Pattern Cladistics versus Numerical cladistics

  • Modern Synthesis versus Cladistic Revolution

  • Dispersal versus vicariance

  • It is said that history is written by the victors. Looking at the above examples we assume that cladistics triumphed over phenetics (overall similarity); Pattern cladistics simply lost a pointless debate; The Modern Synthesis was expelled from numerical revolution and that the dispersalist have finally won in their campaign against the dusty old vicariance biogeographers. In every case above, a heated debate occurred, the problems were addressed and everyone went home feeling like something was resolved. If this is the case why is vicariance still the most prominent theory in systematic biogeography? Why does everyone use phenetic methods? Where have all the cladists gone?

    None of the above debates were resolved. Phenetists kept doing phenetics. The idea of overall similarity (a non-cladistic idea) swept over all of numerical phylogenetics. The pattern cladistics never left, the Modern Synthesis never died and vicariance was never abandoned. If we are to complain that this was all discussed before, then isn't it because the debate never really ended?

    In a recent paper all opposition to DNA Barcoding was dismissed has “... having been controversial” (Lahaye et al. 2008). The paper suggests that by doing DNA Barcoding regardless of its flaws, immunizes it from any criticism. I am sure if another paper is published criticizing barcoding it would be dismissed with that one line "Didn't we discuss this before?" This is the same tactic used by phenetists (overall similarity), Modern Synthesists and Dispersal Biogeographers. It seems that history is not written by the victors, but by those with leaky sinks, a stained carpet and no ambition to do anything about it. But surely "we have discussed this before?"

    References

    Lahaye, R., van der Bank, M. Bogarin, D., Warner, J, Pupulin, F., Gigot, G., Maurin, O.,Duthoit, S., Barraclough, T.G., Savolainen, V. 2008. DNA barcoding the floras of
    biodiversity hotspots. PNAS.10.1073/pnas.070993610395.

    1 comment:

    Joe Felsenstein said...

    "The idea of overall similarity (a
    non-cladistic idea) swept over all of
    numerical phylogenetics."

    No, it didn't. You must misunderstand what "overall" means.