Tuesday, August 01, 2006

"Instant" Evolution Seen in Darwin's Finches, Study Says #6

"Instant" Evolution Seen in Darwin's Finches, Study Says, National Geographic, Mason Inman, July 14, 2006 ...

[Graphic: "Designing Darwin's Finches," Astrobiology Magazine. Continued from part #5]

.... Since then, the 1982 arrival of the large ground finch on Daphne is the first known instance of a new finch arriving in the Gal√°pagos. "The event we observed is the only one that we know about, the only establishment of a new breeding population anywhere in the archipelago," Peter Grant says. [The emphasis should be on "that we know about." As previously mentioned in part #2, since the finches' "ancestral species ... arrived from the South American mainland about two to three million years ago," presumably "the establishment of a new [finch] breeding population ... in the archipelago" has happened tens, if not hundreds of thousands of times.

While this is no doubt exciting for Darwinists like the Grants, who think that "all evolution is due to the accumulation of small genetic changes, guided by natural selection" and therefore "that transpecific evolution [macroevolution] is nothing but an extrapolation and magnification of the events that take place within populations and species [microevolution":

"The proponents of the [Neo-Darwinian] synthetic theory maintain that all evolution is due to the accumulation of small genetic changes, guided by natural selection, and that transpecific evolution is nothing but an extrapolation and magnification of the events that take place within populations and species" (Mayr, E.W., "Populations, Species and Evolution," [1970], Harvard University Press: Cambridge MA, 1974, reprint, p.351).

Therefore they think they are witnessing, before their very eyes, the same process, that writ large, created the finches, birds and all of life in the first place!

But of course if you are not a Darwinist, and don't make that assumption (or leap of faith) that "Macroevolution (major structural transition) is nothing more than microevolution (flies in bottles) [or finch beaks!] extended":

"Orthodox neo-Darwinians extrapolate these even and continuous changes to the most profound structural transitions in the history of life: by a long series of insensibly graded intermediate steps, birds are linked to reptiles, fish with jaws to their jawless ancestors. Macroevolution (major structural transition) is nothing more than microevolution (flies in bottles) extended. If black moths can displace white moths in a century, then reptiles can become birds in a few million years by the smooth and sequential summation of countless changes. The shift of gene frequencies in local populations is an adequate model for all evolutionary processes - or so the current orthodoxy states." (Gould, S.J., "The Return of the Hopeful Monster," in "The Panda's Thumb: More Reflections in Natural History," [1980], Penguin: London, 1990, reprint, pp.155-156)

then all you will see is just a minor episode in an endless ecological cycling of a species' (the large ground finch, Geospiza magnirostris) population extending its range in a time of plenty by invading a new ecosystem (Daphne Major island), which on past history (since it is not already there) it will, in a time of dearth, contract back to its core population range on an adjoining larger island, with no long-term net change.]

"Once this happened before our eyes, we realized we had a very unusual and potentially very important event to follow." [See above and note the "happened before our eyes" and "very unusual and potentially very important event" (my emphasis)!]

The two bird species immediately began competing for larger seeds. [As per usual. The medium ground finch (Geospiza fortis) eats primarily medium to large seeds and the large ground finch (Geospiza magnirostris) eats primarily large seeds. So when they occupy the same ecosystem, according to standard ecological theory they "partition" it into two ecological niches, with the smaller beaked finch specialising on smaller seeds and the larger beaked finch specialising on larger seeds.

As a consequence, one or both finch species' beaks change size to adapt to the size of the seeds they are specialising on.

The real issue is what actually causes the adaptation. As explained in part #2, because of its extreme rapidity, it simply could not be Darwinian natural selection of random micromutations, which requires typically 300 generations for a favourable allele to spread through a vertebrate population.

Therefore, as pointed out in part #1, it probably is an example of "phenotypic plasticity," i.e. "The ability of an organism with a given genotype to change its phenotype in response to changes in the environment."

The Grants actually co-authored a 2004 paper in Science, which showed that the beak size in G. magnirostris (and presumably the other finches) is governed by the expression of a single protein, Bmp4:

"Darwin's finches are a classic example of species diversification by natural selection. Their impressive variation in beak morphology is associated with the exploitation of a variety of ecological niches, but its developmental basis is unknown. We performed a comparative analysis of expression patterns of various growth factors in species comprising the genus Geospiza. We found that expression of Bmp4 in the mesenchyme of the upper beaks strongly correlated with deep and broad beak morphology. When misexpressed in chicken embryos, Bmp4 caused morphological transformations paralleling the beak morphology of the large ground finch G. magnirostris." (Abzhanov, A., Protas, M., Grant, B.R., Grant, P.R. & Tabin, C.J., "Bmp4 and Morphological Variation of Beaks in Darwin's Finches," Science, Vol. 305, 3 September 2004, pp. 1462-1465)

Therefore, despite the obligatory lip service to "natural selection," presumably the latter has little, if anything to do with it (given that as pointed out in part #1, Darwin himself insisted that "natural selection is a slow process" - my emphasis):

"Lastly, natural selection is a slow process, and the same favourable conditions must long endure in order that any marked effect should thus be produced." (Darwin, C.R., "The Origin of Species By Means of Natural Selection," Sixth Edition, 1872, Senate: London, 1994, p.180)

Therefore, it seems that the most likely explanation for this rapid adaptation of beak size to seed size and hardness is a non-Darwinian environmental feedback mechanism that triggers the expression of the gene that codes for protein Bmp4 when the young growing G. fortis finches encounter hard seeds. Or it may even be an environmental trigger that increased the expression of Bmp4 in the G. fortis embryo (which seems to be the implication of this 2004 Heredity paper).

Either way, this would be another claimed best evidence for Darwinism down the gurgler!]

Concluded in part #7.

Stephen E. Jones, BSc (Biol).
`Evolution Quotes Book'

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