Question for Mike #2

The_Fragile
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Question for Mike #2

I was reading The Blindwatch Maker, and came across the section about mutations being random within the constraints of embryological develoment. He used examples such as, humans being unable to sprout wings from their back. I guess I didn't really understand the whole concept. So I was wondering if you could explain this process in a little greater detail. Thanks again Mike.

In reason,

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I hope they cannot see
the limitless potential
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to murder everything.
I hope they cannot see
I am the great destroyer.


Yellow_Number_Five
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The_Fragile wrote:I was

The_Fragile wrote:
I was reading The Blindwatch Maker, and came across the section about mutations being random within the constraints of embryological develoment. He used examples such as, humans being unable to sprout wings from their back. I guess I didn't really understand the whole concept. So I was wondering if you could explain this process in a little greater detail. Thanks again Mike.

In reason,

~Th3_Fr@gil3

Forgive the lateness of my reply.

If we look at the genome of different species, we will find that many species share similar genes. One of the most startling things we found when we began do decode the genome of the organisms that inhabit our planet are how similar they are. Depending on how you measure it, chimps and humans are about 96% on the genetic level, and humans and dandelions are about 33% similar. The difference is how the genotype is expressed phenotypically.

In stickleback fish for example, sticklebacks with hind projections and without hind projections BOTH have the genes for that projection - all the stickleback without the hind projection lacks is a small segment of DNA that initiates the function of many other genes in the embryo. Without that master gene, you won't get the projection. This projection sometimes can prevent the fish from becoming food for other fish, as it makes them tough to swallow, but it also makes them less streamlined, which is a disadvantage when finding food of their own. Hence in populations with large numbers of predators, we see more sticklebacks with the hind projection; less in envioronments where there is less predation.

It is similar in the gene expression between chimps and humans.

We share many of the same genes, but they are expressed differently and to different degrees.

What Dawkin's is essentially alluding to is that while we may share genes with other organisms, that sudden leaps in activating these genes and having the activated genes actually serving a selective function would be difficult to come by. There are humans who are occasionally born with vertebrate tails (coccyx retroposition), and this is a relatively small mutagenic glitch that does not effect the viability of the organism to a large degree. More radical changes are much less likely as they would require a much more extensive and less likely mutation. Humans sprouting wings or even simply being able to produce their own vitamin C, a feature we may have shared with a common ancestor very, very, very, very long ago is essentially statistically unthinkable, wheras sprouting a tail or being born completely covered with hair can and does happen. The vitamin C gene for example exists as a broken gene in chimps and humans, yet canines can make their own.

The genome can only change from the existing genome, and radical changes generally result in non-viable offspring - they are naturally aborted, die in the womb or shortly after birth.

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Yellow_Number_Five
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I'm happy to go into more

I'm happy to go into more detail on how genetic similarity is actually measured and what it actually means, if need be, but hopefully the above answeres your question.

I am against religion because it teaches us to be satisfied with not understanding the world. - Richard Dawkins

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The_Fragile
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Another great answer Mike.

Another great answer Mike. Again I appericate your counsel as always. Don't worry about the late answer I'm sure your a busy guy.

I hope they cannot see
the limitless potential
living inside of me
to murder everything.
I hope they cannot see
I am the great destroyer.