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Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: "Homo troglodytes" Genome Project, DNA 96% {us} | |||||||||||||||||||
RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
It's in the graphs that Sylas made. The actual discussion\conclusion that you refer to was on another thread, this one has the evidence for it. I thought the bonobos were closer to us than troglodytes too.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Your argument fails to show that the morphological differences betweeen humans and chimps exceeds those of every other {species vs Genus} divisions.
Scientists were perfectly able to distinguish superficially very similar animals (such as Echinacea and Hedgehogs) using morphology long before genetic analysis became available, indeed before evolution was even identified. And they also made some mistakes based on just morphology that have been corrected now that we have the genetic information. This is just another such case, but complicated (as noted by Lithodid-Man) by our species-biased outlook. Heck some of us have trouble accepting other races ...
Dogs are considered the same species ... And are also an example of artificial selection which, frankly, bends things somewhat. But that makes them a perfect example of the failure of just morphology as a basis for differentiating species. This is not a refutation of the genetic similarity of chimps and humans. I don't mean to belittle morphology, or relegate it to the scientific dust-bin, but it is one part of the picture of species and higher (artificially constructed human concept) divisions. {abe}: and I have already 'recanted' the "more" in response to MangyTiger
RAZD, msg 3 writes:
There is more morphological (surface differences) than between human and chimp.msg 9 writes: Of all of those differences the only one that I would agree doesn't fit the different dogs is ... Is one difference enough to justify a different Genus? So if one were serious they would catalog the morpological difference between all closely related species and see if there were some common level of {noticeable diffences} that marked such divisions into species, do the same for varieties (like dogs) and see if there is some kind of correlation curve that would take us to genus and above ... and then see where the differences between human and chimp fall on that curve. Sorry to take so long getting back to you, but I am really disturbed by the events in nola, the abject failure to take care of the people just stuns me. This message has been edited by RAZD, 09*03*2005 09:11 AM we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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Lithodid-Man Member (Idle past 2930 days) Posts: 504 From: Juneau, Alaska, USA Joined: |
This may be an aside, but I wonder about the designation of Chimpanzees as Pan troglodytes versus Homo troglodytes. While that is better for our ego I wonder about ICZN rules about precendence. Pan was described as a genus in 1779 (I believe, by Blumenbach). If Robert Bakker is correct in his analysis of Linnaeus' work then the genus Homo was not described formally until 1993. All of the 20th century fossil discoveries claiming Homo as the genus might be suspect. As I understand the ICZN rules then we would become Pan sapiens rather than chimps becomming Homo troglodytes. Holy ego blow Batman!
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.7 |
Lithodid-min,
...genera (not genii, plural of genius not genus) Doh! Sorry.
The numbers of invert congenerics that differ more than that would stagger the imagination. "Invert congenerics" - I don't know the term, please explain?
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.7 |
Your argument fails to show that the morphological differences betweeen humans and chimps exceeds those of every other {species vs Genus} divisions. I didn't say they exceeded "every other" one, I said they were sufficent to grant a seperate genus. Edit actually re-reading my first post, I did, didn't I? I should have said something slightly less absolute. There is more morphological difference between chimps and humans than is usually accepted at a genus level classification.
But that makes them a perfect example of the failure of just morphology as a basis for differentiating species. But I haven't advocated a pure morphological approach. But I do think it has a role to play if our categories are to be useful. Lithodid's point about recognising differences more readily in similar species is a good one though. This message has been edited by Mr Jack, 09-05-2005 07:43 AM
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Ah, middle ground.
But I do think it has a role to play if our categories are to be useful. Lithodid's point about recognising differences more readily in similar species is a good one though Let us say that we share enough characteristics that we could be considered in the same genus in comparison to other species\genus classifications, but that the evidence is not conclusive enough (and the point is still being debated) to make the change at this time. I had some information ona recent proposed reclassification of Pan into the hominidae family, but I've lost the link. Perhaps this is just another reason to change to the phylo-code approach| American Scientist The core proposition of the PhyloCode is to abandon Linnean hierarchical ranks and recognize only species and clades. (A clade is a group of all the organisms that share a particular common ancestor.) The scheme does not dispense with hierarchical organization, as clades will be nested within one another according to phylogeny. The key advantage is that changes made in one part of a classification do not require altering other group names. There is some interesting information here about hominid classifications and that argues for Homo troglodytes ... or to exclude a lot of other hominids from the family?http://www.rfthomas.clara.net/papers/porshnev.html The main criterion for placing fossil forms in the family Hominidae is in practice the presence of accompanying stone implements. Such practice contradicts the purely morphological principle of classification. Before it opens a can of worms, creating more divisions and sub-divisions. There is this MRI study of brain similarities:MRI reveals similarities between the human and chimpanzee brain Studies such as this confirm that human and chimp brains are not only asymmetrical, but asymmetrical in the same way. The findings echo previous looks at the non-limbic parts of chimpanzee brains, which also appear human-like in their patterns of asymmetry. This fact, especially if studied in the context of functional behaviors that reflect asymmetries, may help scientists get a better fix on the evolution of the limbic system in all primates, including humans. But this may also be of interest:http://www.mnh.si.edu/...norigins/whatshot/2002/wh2002-2.htm Humans and chimpanzees share 98.7% of their DNA sequences yet are very different in morphology, behavior and cognitive abilities. According to this paper, these distinctions result not from differences in the protein products produced by the DNA, but in the ways in which the genes are expressed. Gene expression changes can occur when genes are deleted or duplicated, or when levels of transcription factors change. The study found high levels of intraspecific variation in gene expression. They showed that the amount of variation between individuals of the same species was high compared with the amount of variation between chimpanzees and humans. However, a different pattern was discovered in the expression patterns of the brain, with chimpanzees showing greater similarity to macaques than to humans. The human brain had a rate of change of gene expression levels that was 5.5 times faster compared to the other lineages. Could we be looking at "macroevolution" and not recognizing it because we are the ones? Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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Lithodid-Man Member (Idle past 2930 days) Posts: 504 From: Juneau, Alaska, USA Joined: |
quote: I apologize for being unclear. I was referring to invertebrates that are placed in the same genus but differ significantly more than do humans and chimps. In a very real sense the variation within tetrapods even is small when compared to some invertebrate taxa we are comfortable lumping together. As for congenerics I wanted to illustrate using the polychaete genus Prionospio but couldn't find good photos online to link to. Within this genus there are variations in the number of gills. Because they are worms one with two pairs of gills looks pretty much like one with four or seven pairs to us. But what is missed is that developmentally this would be like vertebrates varying by having six limbs or extra pharyngeal pouches within a single genus.
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JustinC Member (Idle past 4843 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
Isn't this argument kindof pointless since all categories above the species level are arbitary?
Common descent is a great (only) explanation for the heirarchial nature by which we classify all life, but it doesn't give us any insights into how we should make our classification. How much genetic divergence do two species need to be considered to be in different genuses? Families? To expect all of our groups across the tree of life to be consistent with regard to mutational distance seems a little absurd. The classifications are meant to help us, not to be some objective reality.
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Chiroptera Inactive Member |
quote: And somethimes the species level, too!
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Perhaps, but we can use the phylo code, and we could talk about "degrees of separation" rather than {genus\family\etc} divisions which are arbitrary and a left-over from the time before genetics (BG)
This would answer problems of ring-species to phylum differentiation while still being able to track interrelations between close relatives. I'll admit to being "old-school" here and have trouble leaving linnaen taxonomy behind. from | American Scientist
The core proposition of the PhyloCode is to abandon Linnean hierarchical ranks and recognize only species and clades. (A clade is a group of all the organisms that share a particular common ancestor.) The scheme does not dispense with hierarchical organization, as clades will be nested within one another according to phylogeny. Now that's all well and good, but how do we convert linnaean to phylo nomenclature?
at least a dozen proposed methods are on the table. Several involve retaining the binomial name (genus, species: Homo sapiens) but formatting it differently to distinguish from clade names, so that human beings might become homosapiens in the Hominid clade. and then we would ask if that puts pantroglodytes also in the Hominid clade, and what is the degree of separation there? one could then look at the number of other branches off either and from that judge the degree of relatedness, and in this regard all the ancestral species of hominid back through australopiticusafarensis would be intermediate species. But it still leaves pantroglodytes as the closest living relative, so that would fomr one clade, whether you considered that {genus} or a {family} differentiation would not be that important. I can't say I know how phylocode deals with {archaic\extinct} species designations. (still learning after all these years) we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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JustinC Member (Idle past 4843 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
quote:True! Stupid nature making things so complicated.
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Chiroptera Inactive Member |
I am (as a non-biologist) a big proponent of cladistics. However, it does seem silly to completely abandon Linnean classification altogether. Linnean classification and phylogenic classification each have their strengths, and I suspect that both are going to be used side-by-side for some time to come.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
The biggest problem I see for the phylo code is how to deal with the nodes of the branches.
Some proposals have been put forward but none I have seen seem too compelling as a system, and when the name used depends on the (arbitrary) order of the branches then we can end up with disagreement on which is "more" correct. Until then we will stagger along with the Linaean system, possibly converting only species to phylo? we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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