Fwd: Re: Human and ape phylogeny

[John Grehan]

>At 10:15 AM 4/4/2003 -0500, Richard Jensen wrote:
>>My first response is that all characters are phenetic - the distinction is
>>based on how we use them.
>
>I'm still confused. I thought the priciple of cladistics - at least as
>proposed by Hennig, was to utilize only those characters that qualified as
>being derived through outgroup comparison while those that were present in
>the outgroup were not included in the analysis. My understanding of a
>phenetic character was that there was no such distinction made.
>
>>Second, it is not necessary to polarize characters in order to conduct
>>phylogenetic analyses.
>
>Agreed. I am not questioning this. I am only interested to clarify my
>understanding of cladistic systematics as to whether cladistics is just
>the analysis of proposed synapomorphies or is it any parsimony or other
>analysis of characters of any or unknown status.
>
>>That can be accomplished by using an appropriate
>>outgroup or by recognizing one member of the ingroup as being basal (a
>>decision
>>that should based on criteria external to the data set being examined).
>
>In this case there appeared to be no criteria involving a group outside to
>that being analyzed (humans and great apes.
>
>John Grehan
>
>
>>Dick
>>
>>John Grehan wrote:
>>
>> > Here's a question for all the cladistic experts on this list. I admit to
>> > having a relatively superficial expertise with cladistics so I want to
>> > measure my current perceptions against any responses on this list. My
>> > question concerns the 'cladistic' quality of an article cited on this list
>> > as increasing the support for a human-chimp/african ape clade vs human
>> > orangutan by S. Gibbs, M. Collard, and B. Wood (2002) Soft-tissue anatomy
>> > of the extant hominids: a review and phylogenetic analysis. Journal of
>> > Anatomy 200: 3-49.
>> >
>> > At first glance the paper seemed very impressive. The authors utilized 171
>> > characters and a cladistic analysis. The number of taxa was limited to
>> > humans and extant apes only which did make me wonder if some of their
>> > characters might not qualify as synapomorphies with further comparison
>> > including at least the old world monkeys. Then I read that "No a priori
>> > judgements were made as to the primitive or derived condition of
>> > characters". My reading of that statement is that the characters were not
>> > 'cladistic' in the sense of each standing as proposed synapomorphies.
>> > Instead they were phenetic.
>> >
>> > The authors then state that "Hylobates was assumed to be the basal
>> hominoid
>> > genus and the cladograms were rooted accordingly". Since the characters
>> > were not defined as synapomorphies with respect to an outgroup, making one
>> > of the taxa the basal lineage seems to be an externally imposed criterion
>> > rather than being generated from the characters themselves. With this root
>> > the characters were subject to 'cladistic' analysis.
>> >
>> > Am I correct to view this paper as a 'cladistic' analysis of phenetic
>> > characters with an arbitrary rooting of one of the taxa being analyzed. If
>> > I am then this paper hardly seems to me to stand up as a reliable support
>> > for the human-chimp clade. I am getting old and perhaps my
>> understanding of
>> > cladistics based on what I read by Hennig, Nelson where cladistics was all
>> > about the analysis of proposed synaomorphies is now out of date and I
>> > missed the boat where cladistics is now all about the analysis of phenetic
>> > characters.
>> >
>> > John
>> >
>> > Dr. John Grehan
>> > Director of Science and Collections
>> > Buffalo Museum of Science
>> > 1020 Humboldt Parkway
>> > Buffalo, New York 14211-1293
>> > Voice 716-896-5200 x372
>> > Fax 716-897-6723
>> > jgrehan at sciencebuff.org
>>
>>--
>>Richard J. Jensen              | tel: 574-284-4674
>>Department of Biology      | fax: 574-284-4716
>>Saint Mary's College         | e-mail: rjensen at saintmarys.edu
>>Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen
>
>Dr. John Grehan
>Director of Science and Collections
>Buffalo Museum of Science
>1020 Humboldt Parkway
>Buffalo, New York 14211-1293
>Voice 716-896-5200 x372
>Fax 716-897-6723
>jgrehan at sciencebuff.org

Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
1020 Humboldt Parkway
Buffalo, New York 14211-1293
Voice 716-896-5200 x372
Fax 716-897-6723
jgrehan at sciencebuff.org