Inferences based on and conclusions drawn from taxonomic classification?

I had posted the below pasted post on salty's "home board". I did so in an attempt to actually discuss one of the underlying "supports" for salty's hypothesis, as mentioned in the manifesto. Basically, the claim is that because "no new genera" of hominid has arisen in the last 2 million years, this is evidence that evolution has stopped:

quote:

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As taxonomic rankings are often arbitrary, is drawing conclusions - or even making inferences - based on taxonomic rankings a logical scientific pursuit?

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Recently, it has been suggested that, for Primates at least, using estimated time of divergence from a common ancestor be used as a criterion for assigning taxa their rank - that is, deciding whether or not species X belongs to one genus or a subgenus, etc.

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Say such a system were adopted. It would require the reworking of many aspects of taxonomy. Would this reworking then demonstrate some 'fact' about evolution?
or would this reorganization have no bearing at all on evolution, and only reflect a name change (if anything)? A different way of doing the same thing?

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I ask as I have recently read something wherein limits are suggested of evolution because of a lack of "new genera" within a certain timeframe.

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Comments welcomed.

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Salty did not comment. Only a creationist named "Don" even attempted any sort of discussion, and this was to make a few snide comments about "evolution science."But it is an important point. If one is going to claim as support for a "no more evolution" claim the 'fact' that there have been no new genera of hominid in 2 million years, it stands to reason that the criteria for establishing a new genus is a fair topic of discussion.Lumpers, splitters, etc. But no comment from the one using this as 'proof.'

Color me ignorant, but isn't the latest breakout that there were three genera at the 2 million year mark? Kenyanthropus, Paranthropus, and Homo, not counting any lingering australopithecines. Heck, I could be wrong - they change the bloody taxonomy so often it's hard to keep up.However, from the Manifesto, I thought salty was proclaiming that Homo sapiens differentiated from Homo neanderthalensis through a hypothetical instant speciation event (although it seems to be a huge leap across an empirical chasm devoid of evidence). IIRC that was about the only mention of human species he made.Oh what do I know? I'm just an ignorant darwinist - not even the armchair variety.

Regarding the meaning of genus, the world taxonomists are curiously silent over this. Wood & Collard (1999) suggested this definition in their discussion of human genera:'The evolutionary systematic definition of the genus is rejected by those who subscribe to cladistic classification, because they do not
accept that paraphyletic taxa are real evolutionary units. However, defining genera solely on the basis of monophyly is equally problematic because there is no criterion for specifying how many species should be included in a genus. A pragmatic solution is to revise the first, gradistic, definition of the genus category (Mayr 1950) so that paraphyletic taxa are inadmissible. Because phylogenetic methods are unable to distinguish between ancestor-descendant and sister group relationships, the problem of how to classify an ancestral species that has a different adaptive strategy from those of its descendants simply does not arise. The problem of
how to classify a terminal species that forms a monophyletic group with one taxon but shares an adaptive strategy with another can be overcome by recognizing the terminal species as an adaptively coherent evolutionary unit and classifying it as a monotypic genus. We suggest, therefore, that a genus should be defined as a species, or monophylum, whose members occupy a single adaptive zone.'Wood, B. & M. Collard. 1999. The human genus. Science 284: 65--71.They suggest that the genus be defined over its adaptive property, or ecologically. By that criterion they pulled out Homo habilis and H. rudolfensis from Homo and name them Australopithecus.

Sorry for the inflammatory subject heading but your question actually leads to another, related basic question. Namely, are species real entities. I read a book a while ago by Niles Eldredge, The Pattern of Evolution, which spent a fair amount of time discussing and answering that question. In short, yes they are real and actually can play, according to the concepts put out in the book, a role in the evolution of larger heirarchical groupings (now I think that you can see why I brought it up here). That said I do not think that time from divergence alone would be a good measure due to the possibility of differing rates of evolution within the different sub-genera and species. This would lead to spurious results. I am afraid that a combination of morphology and genetic analysis, with their obvious limitations, is still a better way of analyzing the relationships.One comment re: the generation of new genera. They each started with one or a few species, older ones have been eliminated through extinction and newer ones split and grow into families ect. This is part of the flaw in the "evolution has stopped" arguement.------------------
"Chance favors the prepared mind." L. Pasteur
Taz

Hi Taz, Since Elvis seems to have left the building, maybe you can help me out. In the part of salty's magnum opus where he talks about speciation, he makes a couple of claims:1) evolution in sexually reproducing organisms has halted. I didn't follow the rationale for this, or what part of sexual reproduction was the mechanism that put the brakes on.2) he seemed to be saying that evolution can occur in single-celled or other clonal species, because a mutation will be inherited.Evolution is therefore either instantaneous or non-existent. Did you follow this part? Can you explain it in words of one syllable so that I can understand at least what YOU think he's saying?

I took it to mean additionally, that that in order to speciate, all organisms had to become asexual. As with everything else I asked, salty never answered, but in recognizing Pan and Homo to be different genera he would not comment on whether the common ancestor was sexually or asexually reproducing. For his hypothesis to work, one would have to posit the unbelievably unparimonious concept that asexual to sexual reproduction occurred independently at every divergence of species...besides being falsifed on morphological and peleontological grounds..it would also not exlain the conserved genetic features of sex determination that salty ignored when I posted references....but as you noted...Elvis has left the building so no answers from him will be forthcoming.

The "no new genera" schtick may have come form the "Ontogeny..." paper, I can't recall for certain now.But the fact remains - if one is hanging their hat on "no new genera", does it not stand to reason that a concrete definition of genus should be employed? As it stands, it seems quite arbitrary, and as I mentioned, different criteria often having nothing to do with the taxa themselves (such as time of divergence) can produce different classifications.if the taxonomic rank is unstable and subject to change, how legitimate are conclusions drawn from the taxonomic name of something?

Actually I would rather finish the document before I comment on the rational behind Salties claims.However, my opinion on the end of evolution is that it has not,...ended that is. I am familiar with some of the general concepts that Salty was talking about, although I think that he has taken some of them to an illogical extreme. The general body plans for the evolution of new species is limited in part by what has come before, ie the parent and grandparent species, ect. This was explored in part in Wonderful Life by Gould and Crucible of Creation by Morris. This limits the top of the heirarchael (sp?) tree, but not the number of variations that can be produced at the ends of the bushes twigs. I agree with the people who Salty cites in that many avenues are largely closed to this series of life forms currently on earth, and I think that the data bears this out. I disagree with the conclusion that evolution is largely over because the number of new species, genera and other taxa that can come, and have been coming, from these basic plans is almost limitless.Hope that this makes sense.------------------
"Chance favors the prepared mind." L. Pasteur
Taz

I think that a lot of it is based on saving the "hopeful monster" idea.The bit about asexual reproduction is (IMHO) intended to solve the problem of where the "hopeful monster" finds a mate.The assumption of guidance is to deal with the problem of getting a viable macromutation - let alone a whole set of them that happen to produce a morphologically distinct species.But can anyone tell this poor confused layman if it even makes sense for a diploid organism to have different chromosmal arrangements for the two paired strands of DNA in its cells ? Or is the idea of being heterozygotic for a chromosomal arrangement completely nuts ?

I think his contention was more subtle than that. He first splits Pan from the lineage leading to Homo prior to 2 mya (true)via an instantaneous chromosome something-or-other (unsupported). His contention then seemed to be that all variation within the lineage was similar to the various breeds of dogs (which he goes on at great length about in his "paper"). Any new species (such as P. paniscus and P. troglidytes or Homo sapiens and H. neanderthalensis) are caused by further instantaneous chromosome thingys OR are false speciation events (i.e., like dog breeds). It smacks a bit of the "variation within kinds" argument. It would have been interesting to see his contention on the hominid lineage challenged.Where it got confusing was describing his chromosome thingy, and how it seemed to both prevent new genera but cause new species. Unless, he meant that no new species could be observed (which is where I got lost).And I got REALLY lost on his sex determination bit. That was probably the most confusing and impossible to follow part of the whole Manifesto.

Thanks Taz. Wow - I didn't pick up any of that from the Manifesto beyond "evolution has ended". I sure didn't see where he was talking about historical constraint (and I remember thinking that he was trying to deny this). I also didn't see where he was limiting his "death knell of evolution" to higher taxa - it really appeared he was saying that NO variation could occur (except rarely, by instantaneous transmutation/saltation) even at the bottom rung. This is why I thought he was denying the evidence from pop gen - and why I was pounding him on the staggered clines and karyotype bit.Man - I simply have to learn to stop arguing with cranks...

Actually much of it was not in the part of the manifesto that I have read so far, but some of it is from his cited sources and some from different interpretations of the data that his sources site. Sorry, I should have been more clear about that.------------------
"Chance favors the prepared mind." L. Pasteur
Taz

Taz, here's an interesting article (I can't yet reach the original PNAS article on-line, I don't think it's posted yet): Hermaphrodite finch hints genes mould brain is a link to the press release. Aside from the article's potential impact on the genetic basis for behavior argument, what do you think of the example as either a support FOR or refutation of salty's hypothesis? Since we have both male and female capabilities in a single organism produced in a single generation (and the PNAS article would hopefully have an explanation of how this occurred), this is saltation at its finest. A living hopeful monster. Or, it could be counterevidence as it was apparently infertile (as would be expected in this kind of chimeric hybrid), thus conforming to standard understanding of post-zygotic barriers - the main argument against the hopeful monster idea.What do you think? (Since yer back in action here - expect lots of questions on various topics. )