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

Cameron,

You wrote:

"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."

Besides the vast oversimplification, I think your presumption here is precisely the problem. While I'm sure there are documentable trait variations that cause noticeable overt changes or increases in survivability in a particular individual, there are vastly more complex issues surrounding the subject of genetic variation, population variation, etc.

As you admit, the 6 inch variation in neck size is very unlikely, so while not impossible, it's not necessarily very useful. I used the .5 cm (times three, in different members of the species) as still an oversimplification, but to illustrate that it is precisely possible that such changes might be due to the "normal variation" in typical height, which is still (presumably) affected by genetic markers, trends, variations, selection, etc. The fact is, you might see 10 successive generations of one species, where the neck height was toward the upper end of the "normal distribution", who later survive to become a dominant population, while their peers fail to survive for any number of reasons. I can imagine that there might have been a particular genetic "transcription error" that conveyed that upward-trending neck length to that particular line, but I think the genetics question is still too little understood on most traits in most species to be able to say for sure. And then, you speak of the "single ancestor" of the modern giraffe, but this just focuses on one aspect, the neck length. I can imagine that it's much more complex than that. For starters, the ancestor "in one trait" as you say, might have different ancestors for different traits.

Again, I'm not trying to defend the Darwinist worldview, but simply responding to the unrealistic nature of your example (six inch change in one generation), as well as the potentially unrealistic assumption that a normal upward-trending distribution pattern can necessarily lead us to point to a single individual where the trend started. It might, but it might not, as far as I can see.

Jon Tandy

From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On Behalf Of Cameron Wybrow
Sent: Tuesday, October 06, 2009 7:01 PM
To: 'asa'
Subject: Re: [asa] Re: Reading Genesis theologically NOT historically

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 Wed Oct 7 09:15:40 2009