Backyard birdfeeders driving avian evolution

To: Andrew Bell <>
Subject: Backyard birdfeeders driving avian evolution
From: Michael Tarburton <>
Date: Tue, 8 Dec 2009 08:42:23 +1100
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


Michael Tarburton


On 07/12/2009, at 11:52 PM, Andrew Bell wrote:

They key is in the statement "almost always" - ie not always. Although artificial selection often retains maladaptive characteristics through human interference, natural selection can be expected to eliminate most maladaptive mutations quite efficiently while selecting for the occasional advantageous one. This is the evolutionary process as generally understood. My understanding is that genetic material is not necessarily lost at all, expression of genes can be turned off and altered, only to be turned on again later in descended species - maybe by changes in bits of DNA we don't conventionally see as genes - it seems we are just beginning to understand a lot of this and the roll of the so called "junk DNA" - watch this space over the next ten years!. Genetic evolution is quite conservative, ie it used and re-uses the same genes, often in new and different ways. I

I don't know where the quote below comes from, but I'm not sure why enhancing one characteristic "is likely to be at the expense of others" , one could just as easily write "is likely to benefit other characteristics". Evolution through the natural selection of novel mutations and rearrangements does indeed enhance the richness of the information - hence the diversity of life birds to marvel at. Just wish they 'ld diverged a bit more at times when struggling to ID those LBJs and waders!


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