deadman_932
Posts: 3094 Joined: May 2006
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Dave says Quote | DEADMAN: [Dead silence on current debate. Changes subject.] "Dave, you need speciation for your theory, not just variation." [We have it. I will cover it here or somewhere.] |
Yet here is what I DID say: Quote | Your scenario calls for a small number of breeding pairs to give rise to millions ( yes, millions...you didn't include plants, bacteria or fungi) of SPECIES not varieties.
I agree that SOME **less-complex rapidly breeding** species like drosophilia ( fruitflies) can successfully move through a bottleneck and diversify [IN VARIATION]...this is not in question...
But you need SPECIES, and lots of them...NOT JUST VARIATIONAL DIVERSITY WITHIN A SPECIES. |
Dave says Quote | I am into EVIDENCE, not theory. Isn't that what scientists (even amateur ones like me) are supposed to be into? And the EVIDENCE says that "recombination does not create new variation", Darwinist wishful thinking notwithstanding. | Well, then you should be able to give the evidence that actually supports your claims on all the subjects we've discussed on your thread...things like carbon dating being wrong ( which you claim is supported by some guy assuming variables without any underlying evidence at all)
At any rate, Dave, I wanted to point out what is obvious to everyone else, but not to you: What Carson is dealing with is polygenic traits...traits that are differentialy affected/created by the influences of MANY UNDERLYING GENES. Variation, following a bottleneck event or inbreeding is GENERALLY expected to decrease by a proportion F, the inbreeding coefficient of the population (WRIGHT, Sewall., 1951 The genetical structure of populations. Ann. Eugen. 15:323-354)
When variation underlying a quantitative trait is controlled by POLYGENICALLY, by genes that act additively within and between loci, the additive genetic variance within a population **CAN** increase. (remember EPISTASIS, Dave?)
This phenomenon has been observed for: (1) morphometric traits (Bryant et al. 1986 ; Bryant and Meffert 1995, Bryant and Meffert 1996) and (2) behavioral traits (Meffert and Bryant 1992; Meffert 1995) in the house fly, and for (3) fitness components in Drosophila melanogaster (Lopez-Fanjul and Villaverde 1989; Garcia et al. 1994) and Tribolium castaneum (Fernandez et al. 1995). One explanation for the increased additive genetic variance following bottlenecks is dominance, the interaction between alleles within a locus. Alan Robertson (The Effect of Inbreeding on the Variation Due to Recessive Genes . Genetics. 1952 Mar;37(2):189–207.), showed that when genetic variance is caused by rare recessive genes, inbreeding or bottlenecks can temporarily increase the additive variance. Willis and Orr (1993) examined the effect of the degree of dominance on the expected additive variance following a bottleneck and found that a broad range of dominance coefficients could cause an increase in additive variance.
Another explanation is epistasis, the interaction among loci. Theoretical work has shown that genetic drift during a bottleneck can "convert" additive x additive [meaning additive TIMES additive, multiplying, in other words] variance (Goodnight 1988; Whitlock et al. 1993) and other forms of epistatic variance (Cheverud and Routman 1996) into additive genetic variance. Thus, provided the proportion of epistatic variance in the ancestral population is high enough, a founder event may result in an increase in additive genetic variance.
Bryant, Edwin H.; Combs, Lisa M.; McCommas, Steven A. Morphometric Differentiation among Experimental Lines of the Housefly in Relation to a Bottleneck. Genetics. 1986 Dec;114(4):1213–1223.
Bryant, Edwin H.; McCommas, Steven A.; Combs, Lisa M. The Effect of an Experimental Bottleneck upon Quantitative Genetic Variation in the Housefly. Genetics. 1986 Dec;114(4):1191–1211.
Bryant, E. H. and L. M. Meffert, 1995 An analysis of selectional response in relation to a population bottleneck. Evolution 49:626-634. Bryant, E. H. and L. M. Meffert, 1996 Nonadditive genetic structuring of morphometric variation in relation to a population bottleneck. Heredity 77:168-176.
Cheverud, J. M. and E. J. Routman, 1996 Epistasis as a source of increased additive genetic variance at population bottlenecks. Evolution 50:1042-1051.
Fernandez, A. and C. Lopez-Fanjul, 1996 Spontaneous mutational variances and covariances for fitness-related traits in Drosophila melanogaster. Genetics 143:829-837
Goodnight, C. J., 1988 Epistasis and the effect of founder events on the additive genetic variance. Evolution 42:441-454.
Lopez-Fanjul, C. and A. Villaverde, 1989 Inbreeding increases genetic variance for viability in Drosophila melanogaster. Evolution 43:1800-1804
Meffert , L. M., 1995 Bottleneck effects on genetic variance for courtship repertoire. Genetics 139:365-374
Meffert, L. M. and E. H. Bryant, 1992 Divergent ambulatory and grooming behavior in serially bottlenecked lines of the housefly. Evolution 46:1399-1407.
Whitlock, M. C., P. C. Phillips, and M. J. Wade, 1993 Gene interaction affects the additive genetic variance in subdivided populations with migration and extinction. Evolution 47:1758-1769.
Willis, J. H. and H. A. Orr, 1993 Increased heritable variation following population bottlenecks: the role of dominance. Evolution 47:949-956.
This is not NEW, Dave, it's been known or suspected for a long time...but it is LIMITED and doesn't give the kind of variation YOU need to sustain a "complex" species AND PRODUCE DAUGHTER SPECIES FROM A PAIR OF ORGANISMS, following a genetic bottleneck 2300 years ago, not **JUST** a "SMALL POPULATION" of MULTIPLE individuals like those found in the Drosophilia example .
DID THOSE DROSPHILIA IN YOUR CITATION SPECIATE? CAN YOU SHOW THAT MAMMALS WOULD UNDER THE SAME CIRCUMSTANCES? NO and NO.
In short, Dave, again you don't KNOW what the he11 you're talking about.
It works fine with SOME VARIATION in SOME TRAITS in SOME RAPIDLY BREEDING species, not ALL variation in ALL Traits in ALL species. AND DAVE? VARIATION IS NOT SPECIATION. VARIETIES OF DOGS =/= (does not equal) NEW SPECIES
The above data was taken from Wang,Jinliang, et al (1998) Bottleneck Effect on Genetic Variance: A Theoretical Investigation of the Role of Dominance. Genetics, Vol. 150, 435-447, September 1998 which gives the mathematical basis for such models. Available online at http://www.genetics.org/cgi/content/full/150/1/435
-------------- AtBC Award for Thoroughness in the Face of Creationism
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