This has the potential to head off topic, so here is a brief example:
Evolution of genes and genomes on the Drosophilaphylogeny
Drosophila 12 Genomes Consortium
Nature 450, 203-218 (8 November 2007)
Abstract
Comparative analysis of multiple genomes in a phylogenetic framework
dramatically improves the precision and sensitivity of evolutionary
inference, producing more robust results than single-genome analyses
can provide. The genomes of 12 Drosophila species, ten of which are
presented here for the first time (sechellia, simulans,yakuba, erecta,
ananassae, persimilis, willistoni, mojavensis, virilis andgrimshawi),
illustrate how rates and patterns of sequence divergence across taxa
can illuminate evolutionary processes on a genomic scale. These genome
sequences augment the formidable genetic tools that have made
Drosophila melanogaster a pre-eminent model for animal genetics, and
will further catalyse fundamental research on mechanisms of
development, cell biology, genetics, disease, neurobiology, behaviour,
physiology and evolution. Despite remarkable similarities among
theseDrosophila species, we identified many putatively non-neutral
changes in protein-coding genes, non-coding RNA genes, and cis-
regulatory regions. These may prove to underlie differences in the
ecology and behaviour of these diverse species.
On 08/12/2009, at 7:42 AM, Michael Tarburton wrote:
G'day All who are following this thread that Laurie so kindly
brought to our attention.
Ok I said "almost always" because it is known in science (&
hopefully common sense) that it is very hard in practical terms to
exclude every possibility. ie. to prove something all you have to
do is show that it is true in one or more cases. To disprove
something you have to have investigated all cases - how do you know
when you have achieved that? In many situations you cant so you
have to look at probabilities.
So can you come up with an example of an "occasional advantageous
genetic mutation"? If you cant then this aspect of evolutionary
theory is baseless.
Going back to the original example of the Blackcap Sylvia
atricapilla we can use Darwinian or neo-Darwinian selective theory
to explain that those birds going to the UK instead of Spain would
have an advantage in that they are better fed in winter and have
less distance to return to their breeding grounds. This means they
arrive at the breeding grounds in better condition and earlier than
the birds wintering in Spain. David Lack's research shows this
probably gives them the choice of the best breeding sites and
greater success in producing more offspring than those going to
Spain. In time they will (have?) outnumbered the other portion of
their population.
I see no problem with that - and they probably can revert to the
other form if conditions change back (but that varies between
characters) but they are still blackcaps no new genes have been
produced just an advantage to those whose genes allowed them to go
to the UK instead of Spain. This is similar to Biston betularia the
Peppered Moth that was touted in Uni & high school text books ad
nauseam as examples of evolution. Problem is they are still
Peppered Moths and they have started to revert to the lighter form
and the evidence is that they started to do so before the UK started
their clear air program. Problem with that example is that much of
the research has been shown to be faulty & fraudulent. [see
Evolutionary Biology 30: 299-322. The Scientist 13(11):] That has
not stopped some text books still using it.
The examples of Darwin's finches is not too different. Now that good
times have returned to the Galapagos Islands (at least for the
finches) the heavy-billed birds have lost their advantage and are
returning to the narrow-billed form. This is not evidence for the
development of new genes. is is evidence that Darwin's selection
pressures can select for certain genes under certain circumstances.
Nothing new has been created.
So there is good evidence that the environment can selectively
favour certain genes but I am still waiting for just one example of
a new gene having evolved.
Cheers & happy thinking
Mike
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Michael Tarburton
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www.birding-aus.org
birding-aus.blogspot.com
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