Darwinism Genetics

Biology prof: Darwin’s finch variations may also be driven by “hidden genes”

Spread the love

Re Darwin’s finches not a good example of Darwinian evolution? (Because they are so heavily hybridized):  David A. DeWitt writes to say:

When considering the ‘evolution’ of the finches, we also need to take into account hidden genes. These are genes that, while present in the population, are not linked to an observed phenotype. For example, I crossed a brown mouse and a white mouse and the offspring were all grey. When the grey mice were crossed, the next generation included mice that were white, brown, white with brown spots, white with grey spots, a grey/brown mix, and one that was yellow. All of these varieties were derived from the same ancestral pair, yet all of these coat color traits were hidden and only showed up in successive rounds of inbreeding and within 2 generations. There were no mutations, just different combinations of genes.

The same thing is likely happening with finches, with Ensatina salamanders, Hawaiian honeycreepers and a variety of other populations of organisms.

He adds,

See the issue is some genes will mask the expression of others. Two of my daughters have red hair, but my wife and I both have brown hair. That means we both have genes for red hair but you can’t tell. If we married other people, we would be passing on genes for red hair in the population, but you couldn’t tell unless our children happened to marry and then voila: red hair.

So what might look like evolution (change in gene frequency over time) may simply be fluctuation in the expressed genes that are part of the variation in the population from the beginning.

Thoughts?

It strikes a layperson that a variety of genetic patterns that do not display in a given generation could help account for the tenacity of life forms such as the mouse—in a world where thousands of species are on the endangered list. But not mice. Never mice. (Never rats either, worse luck.)

Readers may remember neuroscientist deWitt from: Contemplating Bill Nye’s 51 skulls slide, where the discoveries mad in Nye’s absence are more informative than those made in his presence.

Follow UD News at Twitter!

19 Replies to “Biology prof: Darwin’s finch variations may also be driven by “hidden genes”

  1. 1
    Zachriel says:

    David A. DeWitt: So what might look like evolution (change in gene frequency over time) may simply be fluctuation in the expressed genes that are part of the variation in the population from the beginning.

    The fifteen or so species of Darwin’s finches do not all have the same set of genes differently expressed.

    http://mpkb.org/_media/home/pa.....logeny.jpg

    http://www.nature.com/scitable.....lanmax.jpg

  2. 2
    Zachriel says:

    Better image of the phylogeny of Darwin’s finches.
    http://scienceblogs.com/starts.....nches.jpeg

  3. 3
    Joe says:

    Zachriel:

    The fifteen or so species of Darwin’s finches do not all have the same set of genes differently expressed.

    Your links do not support your claim.

  4. 4
    Joe says:

    In 1967 100 identical finches were released on atolls in the Pacific. Within 17 years these once identical finches diversified- morphological beak differences along with the accompanying musculature and behavioral differences.

    All within 17 years.

  5. 5
    Bob O'H says:

    So what might look like evolution (change in gene frequency over time) may simply be fluctuation in the expressed genes that are part of the variation in the population from the beginning.

    When we look at evolution we’re looking at populations, not single crosses. So any variation due to dominance and epistasis gets averaged out pretty quickly, and if it’s expressed as variation it’s expressed as standing variation.

  6. 6
    Joe says:

    Bob:

    When we look at evolution we’re looking at populations, not single crosses.

    The part you were responding to said “population”. What is your point?

    So any variation due to dominance and epistasis gets averaged out pretty quickly, and if it’s expressed as variation it’s expressed as standing variation.

    Your point?

  7. 7
    ppolish says:

    Hidden Genes & Hybridization leading to a plethora of beak shapes makes a lot more sense than birds randomly pecking on rocks and Naturally Selecting mutant beaks over the eons. NS & RM a minor player, even with the Famous Finches.

  8. 8
    wd400 says:

    As Bob says, “hidden” phenotypes can stay hidden in a pedigree for a few generations. They can’t stay hidden in a population. The Darwin’s Finches paper also talks about the actualy genetic changes that have gone on in these species….

    It strikes a layperson that a variety of genetic patterns that do not display in a given generation could help account for the tenacity of life forms such as the mouse—in a world where thousands of species are on the endangered list. But not mice. Never mice. (Never rats either, worse luck.)

    I don’t see how. And, FWIW, there are plenty of endangered mouse and rat species.

  9. 9
    News says:

    wd400 knows perfectly well that I was referring to the common house mouse (mus musculus) and the common rat (rattus Norviegicus).

    Funny what people have to do these days to make their point.

  10. 10
    wd400 says:

    I didn’t know that, when someone says “rat” I presume they mean “rat”. Especially as there are multiple species of “common” rats, and you seemed to be suggesting some property of mouse and rats generally.

    If I was mistaken, then sorry. But I’m still at loss as to how the existance of dominant and recessive genes could explain the hardyness of of some mouse and rat species. I guess perhaps heterozygote advantage could conceivably play a role… but that’s evolution

  11. 11
    Joe says:

    wd400:

    As Bob says, “hidden” phenotypes can stay hidden in a pedigree for a few generations. They can’t stay hidden in a population.

    Sure they can, especially if some epigenetic factor is required to activate them. This is exactly what happened in Mexico with the Axolotl.

  12. 12
    wd400 says:

    Joe. DeWitt is talking about dominance effects, and perhaps epistatic interactions among alleles at different loci.

    Enivronmentall induced epigeneti effects might lead these sort of “hidden” phenotypes, but that couldn’t explain the finches where multiple species share the same habitat but nevertheless have distinct heritable differences which are explained at lest in part by particular genetic sequences.

    I suspect you are mistaken about Axolotl evolution, but I’m not even going to bother asking how you think that went down.

  13. 13
    ppolish says:

    A bit OT maybe…new statement on the http://www.thethirdwayofevolution.com website:

    “It has come to our attention that THE THIRD WAY web site is wrongly being referenced by proponents of Intelligent Design and creationist ideas as support for their arguments. We intend to make it clear that the website and scientists listed on the web site do not support or subscribe to any proposals that resort to inscrutable divine forces or supernatural intervention, whether they are called Creationism, Intelligent Design, or anything else.”

    Third Way Evolution = Darwin Finches may not be the almighty NS & RM, but it ain’t the almighty Almighty either.

  14. 14
    Joe says:

    Axolotl- a Mexican delicacy. When taken back to Paris they were placed in a lake that contained some amount of iodine. This allowed them to further their development, ie reach adulthood.

    And again, in 1967 100 identical finches were released to Pacific atolls. There weren’t any finches there to begin with. Within 17 years there was observed variations in both morphology of the beaks with the accompanying musculature and behavioral changes as well. Much too fast for unguided evolution to produce.

  15. 15
    Bob O'H says:

    Joe @ 6-

    Your point?

    I was a bit too concise – sorry! My point was that De Witt was saying that with some crosses he can get a lot more phenotypic variation in the offspring than is seen in the parents. This isn’t controversial. But he then suggests that this could result in changes in variation at the population level. Yes, there can be crosses like those he describes in a natural population, but if there is no selection these will be constant (plus or minus stochastic variation) over time, so overall there won’t be any change in the proportions of the different offspring phenotypes, except by genetic drift.

    The only exception I could see would be if there was a change in mate preference over time, but I can’t see how that could be a general pattern that would be a general explanation.

  16. 16
    Joe says:

    Bob O’H:

    Yes, there can be crosses like those he describes in a natural population, but if there is no selection these will be constant (plus or minus stochastic variation) over time, so overall there won’t be any change in the proportions of the different offspring phenotypes, except by genetic drift.

    How can we test that? For one to see if there wasn’t any selection and then to see how the population shapes up?

  17. 17
    Bob O'H says:

    Joe – it’s not trivial, but we can use methods from quantitative genetics, for example see these two links:
    http://nitro.biosci.arizona.ed.....wvol2.html
    http://rstb.royalsocietypublis.....1.full.pdf

  18. 18
    Joe says:

    I doubt it is as black and white as you think, Bob. Selection pressures change.

  19. 19
    DavidD says:

    This is an interesting article this evening on how non-Darwinian mechanisms as opposed to his Tinker Bell (Natural Selection) are the creators of change. Here is the first paragraph:

    “At a time when endorsement of Darwinism is reflexively identified with belief in evolution, it may come as a surprise that alternative accounts are gaining acceptance. Scientists studying the history of life on Earth are increasingly moving beyond the nineteenth-century theory, and concepts and insights that were unknown to the founding figures are now on the table. A recent commentary section in that most mainstream of scientific journals, Nature, titled “Does evolutionary theory need a re-think,” pitted researchers who answered, “No, all is well,” against ones asserting, “Yes, urgently.” Denis Noble, a senior figure in British physiology, has recruited a group of investigators from multiple evolution-related disciplines to describe their work on a website that advances the proposition that mechanisms other than natural selection “would better explain evolution processes.” None of these critics of Darwinism is a creationist.”

    And the die hard defenders hate it with a passion. There were several beautiful new terms expression brought up and I think this one allows for a replacement of the false religious term, “Junk DNA” – Look here –

    “Precipitating events can include mutations in certain “toolkit” genes.”

    So ‘Junk DNA” could really be “Tool-Kit Genes”

    http://www.huffingtonpost.com/.....01678.html

Leave a Reply