Daniel Smith
Posts: 970
Joined: Sep. 2007
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| Quote (Albatrossity2 @ Feb. 13 2009,18:27) | | Quote (Daniel Smith @ Feb. 13 2009,19:24) | Albatrossity,
Let's take a look at this and see what we actually have here.
Polyploidy is common in the plant world: | Quote | | Polyploidy is an important evolutionary force. Recent estimates suggest that 70% of all angiosperms have experienced one or more episodes of polyploidization. The frequency of polyploidy in pteridophytes could be as high as 95% |
The polyploid production of these Tragopogon varieties is a repeatable and frequent occurence: | Quote | | Tragopogon mirus Ownbey and T. miscellus Ownbey are allopolyploids that formed repeatedly during the past 80 years following the introduction of three diploids (T. dubius Scop., T. pratensis L. and T. porrifolius L.) from Europe to western North America. |
| Quote | | Tragopogon miscellus and T. mirus, two allopolyploid species of goatsbeard, may have formed as many as 20 and 12 times, respectively, in eastern Washington and adjacent Idaho (USA) in only the past 60–70 years; multiple polyploidizations have even occurred within single small towns. Studies of recent allopolyploidy in Tragopogon indicate that multiple origins can occur frequently over a short timespan and in a small area. |
In polyploid varieties, the genetic distance between parents determines the amount of change in the resultant progeny: | Quote | | Therefore, Brassica provides two important suggestions regarding genomic change after polyploidization: (1) the more divergent the parents, the greater the subsequent genomic change in the polyploid; and (2) the nuclear genome of maternal origin experiences less change than the paternal contribution. |
| Quote | | Analyses of rDNA ITS (internal transcribed spacer) + ETS (external transcribed spacer) sequence data indicate that the parental diploids are phylogenetically well separated within Tragopogon (a genus of perhaps 150 species), in agreement with isozymic and cpDNA data. |
link and link
So what we have here is the normal product of polyploid reproduction in plants that are hybridized from two distantly related parents. It works like recombination only with two (or more) copies of the genome.
(BTW, the term "speciation" is a term largely without meaning - since the term "species" is essentially undefined.)
Now you want to suggest this as an answer to my challenge for a new biological system with known precursors. OK, let's assume you're correct. This is the evolution of an entirely new morphological feature in one step. All the enzymes are pre-positioned and pre-regulated. The biochemical pathways are functional and intact - in one step. If this is evolution (and technically it is), it's much more like the saltational evolution predicted by Berg, Schindewolf, Davison, Goldshmidt et al, than that predicted by Darwin.
In fact, the Soltis, Soltis paper on multiple origins reads a lot more like Berg's Nomogenesis, than Darwin's Origin: | Quote | From Nomogenesis:
"Evolution bears a sweeping character, and is not due to single, accidentally favourable variations." (pg. 400)
"...evolution is... an unfolding or manifestation of pre-existing rudiments." (pg. 403)
"The evolutionary process should be imagined in the following manner. A considerable quantity... of primitive organisms have developed on parallel lines, convergently experiencing approximately the same transformations and effecting that process at various rates" (pg. 404)
"Species arising through mutations are sharply distinguished one from another." (pg. 406)
"...evolution was chiefly convergent (partly divergent)... based upon laws... affecting a vast number of individuals throughout an extensive territory... by leaps, paroxysms, mutations" (pg. 406)
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It also presents strong evidence in favor of Goldschmidt's hypothesis that the unit of evolution is the chromosome rather than the gene.
It's also strangely reminiscent of prediction I made way back when...
| Quote | | Phylogenetic trees will produce results that will increasingly rely on gene swapping and other mechanisms that cause large scale genetic changes. |
link
Are you sure you want to cite this example Albatrossity? |
Quit handwaving.
The fact that this is "normal", or "common" is an argument for my side. You are the fellow who claims that there are no examples of complex systems for which we know the immediate precursors. The fact that there are lots of them, including this one, is NOT an argument in your favor in any rational universe.
So, yeah, I'm sure that I want to cite this example, or any of a few dozen other examples, because it proves my point, rather than yours.
I assume, from your convoluted yet totally irrelevant comment, that you finally agree that this is an actual example of a complex system for which we know the immediate precursors.
If so, thanks for playing. If not, tell me your latest argument for why this is not the case.
eta - First rule of holes: When you are in one, stop digging. When will Daniel stop digging? When will he understand the contradiction in simultaneously asserting that this example is something that he claims never happens, and yet it is also cleverly predicted by the theories of his scientific heroes? The mental contortions engendered by a conclusion-first approach to science will never cease to amuse me!
eta II - Daniel, do you understand that you were hilariously wrong when you said that this was an example of "recombination"? Will you admit that you were wrong? Or were you hoping I would forget that great moment in the history of hubris? |
So what is the mechanism by which this evolution (of a new morphological feature in one step) was accomplished?
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"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." Orville Wright
"The presence or absence of a creative super-intelligence is unequivocally a scientific question." Richard Dawkins
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