Re: [asa] Re: Reading Genesis theologically NOT historically

Cameron, what I am objecting to is your erroneous thinking about how "traits" work genetically and how speciation works. Yes, variation enters a population through mutation and within an individual. No, continuous traits are not controlled by single genes, nor would a single mutation be likely to cause such a marked change in one individual. No, populations do not derive from single ancestors or ancestral pairs, except in the rarest of cases.

Again, an introductory text on genetics, with reference to the population genetics and quantitative genetics sections, would be advised.

Any progress on that paper?
Dennis

On 06/10/09 5:01 PM, "Cameron Wybrow" <wybrowc@sympatico.ca> wrote:

Jon:

First, the giraffe example isn't mine; it's the standard example that's been used to promote Darwinism in both textbooks and popular science presentations since time immemorial. I was "defending" it not because I find Darwinian explanation probable (I don't), but because Dennis does accept such explanations, and I didn't see how his remarks squared with it.

Second, I'm not sure I follow your example. You mention three giraffe ancestors, one with a .5 cm increase, one with a 1 cm increase, and another later on with a .5 cm further increase. Do the two with later increases both descend from the first one, and are the increases they display "built on", so to speak, the genomic changes initiated by the first one? If so, then in Darwinian terms, it is the first one who should be called the giraffe ancestor. (I am presuming, of course, that the increase in the first one was not due to the "normal variation" of height typical of that population, but was a genuinely new trait, caused by a mutation, that had never previously existed in the population.)

Of course, in selectionist terms, it is very unlikely that a jump of merely .5 cm would give a decisive advantage to the creature in reaching higher leaves; that is why I suggested a more dramatic jump of six inches, which would make literally tens of thousands more leaves available to the creature during a time of food shortage.

Regarding the fossil record, I was not claiming that we could ever in practice locate the bones of the first individual with the mutation in question. Nor, obviously, do we have any remaining genetic material from giraffe ancestors to analyze. My argument is not empirical, but conceptual. I was claiming only that a first individual with a trait must exist before that trait can enter the population. And I still don't know why Dennis cannot simply grant this. It's hardly even biology, it's mostly just logic.

Cameron.

----- Original Message -----

From: Jon Tandy <mailto:tandyland@earthlink.net>

To: 'asa' <mailto:asa@calvin.edu>

Sent: Tuesday, October 06, 2009 11:01 AM

Subject: RE: [asa] Re: Reading Genesis theologically NOT historically

Cameron,

Just a question about the okapi example. What if the offspring of the five-foot animal was not five foot six (presumably an unlikely event), but five foot plus half a centimeter, with the extra half centimeter being in the length of its neck. What if three generations down the line, there was a descendent who was five foot plus a full centimeter. Offspring for several generations might have been similar, within a degree of normal variability. What if ten generations later one of the offspring of one of those lines had a neck that was another half centimeter longer, while many of its cousins had been killed off through various environmental events. And so on, until there was a population, maybe 1000 generations later, whose survival had preserved the longer-neck genes and became what we call the giraffe.

At what point in this sequence would you identify the first *giraffe* ancestor? Which half centimeter (or quarter centimeter, to make the challenge more difficult) increase in which lineage would classify as being the first? Biologists would tell us that the *first individual* of the population is in most cases immaterial, that the migration of population and genetic traits over time are what's more important.

I have no idea whether this is how it happened, and I suspect that biologists don't really *know* either, but infer something like the above from the gradual nature of the (incomplete) fossil record. It could have been entirely different, with one mutant having a half-foot longer neck and also happening to be the lucky survivor when most of his fellow population got killed, being the proud father of longer necked descendents to a new population. But unless one could find the complete fossil record of every generation before and after that individual (and be able to prove that the fossil record was unbroken), there would be no way to prove that there was a first distinctive individual. Am I wrong?

Jon Tandy

From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On Behalf Of Cameron Wybrow
Sent: Tuesday, October 06, 2009 2:10 AM
To: asa
Subject: Re: [asa] Re: Reading Genesis theologically NOT historically

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Received on Tue Oct 6 22:30:25 2009