Backyard birdfeeders driving avian evolution

To: "Andrew Bell" <>
Subject: Backyard birdfeeders driving avian evolution
From: Michael Tarburton <>
Date: Mon, 7 Dec 2009 21:50:45 +1100
G'day All

Andrew suggested:
"There are many examples of such minor changes in bird populations being
cited as evidence for observable evolution, including melanotic urban rock doves. Darwin hypothesised that the development of all species was due to
the gradual accumulation of just such minor variations over very long
periods of time."

But there is a problem here:
Selective breeding to enhance certain characteristics has long been common farming practice. Darwin pointed to artificial breeding such as this in his book On the Origin of Species. He saw it (as many still do today) as showing that selection can give uphill improvement, which could eventually lead to totally new creatures. However, he was unaware that enhancing one characteristic through selection is likely to be at the expense of others. This is logical, since selection creates no new information, it only 'chooses' from what is there. As a variety becomes more specialised through such selection, it loses some of the genetic richness of its ancestors.

This means that each new variety of dog & pigeon or whatever, has lost some of the original genome and can never get back to the original ancestor by selective breeding amongst the same breed. Though I guess Peter is correct if you let them breed between the different breeds you would get at least some of the way back to the original Rock Dove or Wolf. But that is not evolution and actually demonstrates what I said above about selective breeding actually selecting some genes and losing others - not making new ones.

To get new genes you need mutations (or at least that is what most uni texts say), but the problem here is that mutations are almost always deleterious so that does not support evolutionary processes either.

So here is to more happy thinking.


Michael Tarburton



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