cladism's greatest weakness

Tom DiBenedetto tdib at UMICH.EDU
Wed Sep 22 19:01:41 CDT 1999

Ken Kinman wrote:

>     The notion or assumption that an ancestral species becomes extinct at
>the moment of cladogenesis (and then becomes two new daughter species) was
>proposed by Hennig, but I believe he regarded this as just a methodological
>assumption (perhaps to get around the problem of budding).
>     But I get the distinct impression from strict cladists today that many
>actually believe this is some kind of real evolutionary event.

Could you refer me to a single cladist who has ever said anything that
even approximates this?

>I guess the
>thought that the original species could survive unchanged by the budding off
>of a small peripheral population----well, it's just too paraphyletic for
>them to contemplate seriously.

But obviously this issue has nothing to do with the survival of any
population; it has to do with what we choose to recognize with a name.

>By now, I would guess most students are
>never presented this dilemma, and Hennig's methodological assumption is
>often presented as reality.

Pretty bad guess. I have never in my life run across the "ancestral
species go extinct" notion except as a long-forgotten proposal in
Hennig's book.

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