Freethought & Rationalism Archive

Quetzal · 02-19-2002, 01:19 AM

I've run across a new creationist subspecies. This one apparently accepts natural selection as a mechanism for speciation. However, he postulates some kind of limitation on the number of potential species that can develop from a single parent lineage. This "limit" is what he's calling "programmed variability". To wit:

Quote:

Speciation should occur as a product of the great variability programmed into living things, combined with mutations.

This is such an odd statement I thought I'd share it with y'all and see what responses we can come up with. (I've already asked for some evidence of what programmed variability means - i.e., how is it recognized, what are the limitations, etc.) He also mentioned two corollaries to this idea (or explanations?):

Quote:

The overall diversity of species INCREASES over time.
The overall diversity of the new species is less than that of the first species

I've already pointed out he's conflating biodiversity and inherited variability, but beyond that I'm not quite sure what he's trying to say.

Anyone ever heard of this before? Anyone have any good responses?

[Edited to add additional background]

Quote:

For example: Let's say Darwin's finch traveled to the Galapagos. The first two finches had enormous variability programmed into the way their beaks may be. After droughts and environmental conditions or whatnot, certain forms of these beaks begin to become advantageous. Natural Selection picks them over time. Now we have 13 different species with different beaks. But, two Finches with beak A cannot mate and produce babies with beak B. Similarly, beak B finches cannot produce beak A offspring. Therefore, the variety of the species of finch has increased, yet the variability within each species of finch has decreased.

My response:

Quote:

Biodiversity refers to the relative numbers of different species within an ecosystem. We often talk about the “richness” of biodiversity. For example, a tropical rainforest is “richer” in biodiversity than a temperate pine forest, because there are simply more, different species for the same size geographical area. Variability refers to the relative frequency of different traits (alleles) within a species. For example, among butterflies there is huge variation in coloration and patterning within a single species – so much so that often only an expert with time on their hands can tell whether a particular specimen is the same or a different species.

Speciation occurs by natural selection (which you apparently accept) operating on inheritable variability. IOW, variability causes (or permits, anyway) biodiversity. I guess my question is: how does an increase in biodiversity translate into a decrease in inheritable variability? By observation, it appears the opposite is true: more species yields more opportunities for mutation to create novel alleles for natural selection to operate on. It isn’t a zero-sum game. The parent species in the Galapagos example gave rise to 13 new daughter species – the parent species is still living in Ecuador. In point of fact, there’s a fourteenth daughter species living on Cocos Island (about 850 km from the Galapagos). Simply because they are different species and can’t inter-breed does not mean there is any loss of variability within species.

[ February 19, 2002: Message edited by: Morpho ]</p>

Blinn · 02-19-2002, 02:29 AM

I've also encountered this recently. The cretinist maintains that there is an "original genetic endowment" that was carried among the 2 or 7 of each "kind" on the alleged ark. The processes of natural selection and genetic drift narrowed this original diversity (de-evolved?) into today's species, and the reason for today's loss of biodiversity is due to species inability to adapt because of their lack of variation!

And her prime example of this is the cheetah which I used an example of a "bottleneck" when I was foolishly trying to educate her.

I decided to play her a game for a while, which limits a gene to a maximum of 14 alleles, since she maintains that all genetic variation existed in a maximum of 7 founder animals. I showed her a study of leopards that demonstrated they have high genetic variation and in some case, far more than 14 alleles for a gene. Of course this was all ignored...

<img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

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02-19-2002, 02:29 AM	#2
Blinn Veteran Member Join Date: Aug 2001 Location: Ohio, USA Posts: 1,162	I've also encountered this recently. The cretinist maintains that there is an "original genetic endowment" that was carried among the 2 or 7 of each "kind" on the alleged ark. The processes of natural selection and genetic drift narrowed this original diversity (de-evolved?) into today's species, and the reason for today's loss of biodiversity is due to species inability to adapt because of their lack of variation! And her prime example of this is the cheetah which I used an example of a "bottleneck" when I was foolishly trying to educate her. I decided to play her a game for a while, which limits a gene to a maximum of 14 alleles, since she maintains that all genetic variation existed in a maximum of 7 founder animals. I showed her a study of leopards that demonstrated they have high genetic variation and in some case, far more than 14 alleles for a gene. Of course this was all ignored... <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

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