[Taxacom] Type of Homo sapiens (was: Are species real? Doesn't matter.)

[Vazrick Nazari]

Richard,
I have a hard time placing the ‘existence of a clade’ in the same category with the ‘existence of atoms’ or ‘existence of multicellular organisms’. To me, clades are just as real as species. The scientific reasoning (and support) for existence of different clades can be variable to a great extent, just like species can be delineated with various degrees of certainty (re. Tautaras, versus whatever species-complex out there that works for you). Unlike your other examples, the existence of a clade (defined as ‘a group of biological taxa that includes all descendants of one common ancestor’) can just as easily be threatened as the existence of species. Reproductive events cannot be the “definable and mostly unambiguous boundary” of a clade. Monophyly is the only “definable and mostly unambiguous boundary” of a clade. As far as I know, any violation of the principle of monophyly will undermine the existence of a clade, and this violation happens quite regularly in phylogenetics
 and taxonomy. Clades are being re-shaped or nullified all the time, just as species are being shuffled into various genera or synonymized with one another all the time. Existence of any clade is dependent upon the amount of data available and the methodology used for inference, just as existence of species depends upon the amount of data available and the species definition adopted.

For what it is worth 

Vazrick Nazari, PhD student
Department of Integrative Biology
101 Axelrod Building, University of Guelph
Guelph, Ontario, Canada N1G 2W1
Phone: (519) 824-4120 ext. 52226
http://www.uoguelph.ca/~vnazari



Richard Pyle <deepreef at bishopmuseum.org> wrote: 
Hi Dick,

We have good scientific reason to believe that subatomic particles exist.
We have good scientific reason to believe that atoms exist.  We have good
scientific reason to believe that molecules exist.  We have good scientific
reason to believe that living cells exist. We have good scientific reason to
believe that multicellular organisms exist. We even have good scientific
reason to believe that clades exist.  We do NOT have any reason to believe
that "species" exist.  What separates the first six things from the last is
that they all have definable and mostly unambiguous boundaries (in the case
of clades, these are reproductive events -- as in the most recent
reproductive event that is shared in the evolutionary histories of all
extant organisms within a defined set).  Specifically, they have boundaries
that exist whether or not human beings exist.  The boundaries that we define
for species (i.e., the circumscription of all individual organims -- alive,
dead, and yet-to-be-born) are simply that -- definitions that we create.
Subatomic particles, atoms, molecules, cells, multicellular organisms and
probably even clades are units that exist in nature whether or not humans
are here to observe them.

Aloha,
Rich


 
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