Potential falsifications of the theory of evolution

Click on the "Search" link at the top of the page. For "Search Terms" enter "genetic drift" between double quotes. For "Search Forum or Category" select "Search All Open Forums". For "Search by Author Name" enter "Percy". Click on Search. Peruse the results going back to 2001. Evidently I've been familiar with the term for a long time.Now change "genetic drift" to "Kimura" and repeat the search. Peruse the results going back to 2002. Evidently I've been familiar with Kimura's work for a long time, too.So since I'm familiar with genetic drift and Kimura, you must have misunderstood my answer. Where you've gone wrong is that you've forgotten what you're defending. Back in my Message 104 I quoted Sanford, saying:

Let me explain the contradiction again. Sanford says these mildly deleterious mutations are "too subtle" individually to be subject to the natural selection filter, and that they accumulate over time and degrade fitness. When deleterious mutations have aggregated to the point where they degrade fitness then this aggregation is not "too subtle" to be subject to natural selection. Natural selection would operate against aggregations of deleterious mutations degrading fitness.

Sorry if I wasn't clear. Of course climate change of any sort affects selection. The scenario was supposed to be one of rapid climate change within a single generation, causing previously advantageous traits like hairlessness to become deleterious. Let me illustrate this another way. Say you transported hairless creatures from the desert to the North Pole. Their advantageous alleles for hairlessness would suddenly be deleterious. What is advantageous or deleterious is often a function of environment.

The point I was making is that genetic processes will not cause aggregations of deleterious mutations to spread throughout a population and degrade fitness. Natural selection would operate against this. And if you want to argue that such aggregations have too subtle an effect for natural selection to operate on, then since there is no effect on survival to reproduce there cannot have been any degradation in fitness.

Although both processes drive evolution, genetic drift operates randomly while natural selection functions non-randomly. This is because natural selection emblematizes the ecological interaction of a population, whereas drift is regarded as a sampling procedure across successive generations without regard to fitness pressures imposed by the environment. While natural selection is directioned, guiding evolution by impelling heritable adaptations to the environment, genetic drift has no direction and is guided only by the mathematics of chance.[20]As a result, drift acts upon the genotypic frequencies within a population without regard their relationship to the phenotype. Changes to the genotype caused by genetic drift may or may not result in changes to the phenotype. In drift each allele in a population is randomly and independently affected, yet the fluctuations in their allele frequencies are all driven in a quantitatively similar manner. Drift is blind with respect to any advantage or disadvantage the allele may bring. Alternatively, natural selection acts directly on the phenotype and indirectly on its underlying genotype. Selection responds specifically to the adaptive advantage or disadvantage presented by a phenotypic trait, and thus affects genes differentially. Selection indirectly rewards the alleles that develop adaptively advantageous phenotypes; with an increase in reproductive success for the phenotype comes an increase in allele frequency. By the same token, selection lowers the frequencies for alleles that cause unfavorable traits, and ignores those which are neutral.[21]In natural populations, genetic drift and natural selection do not act in isolation; both forces are always at play. However, the degree to which alleles are affected by drift or selection varies according to population size. The statistical effect of sampling error during the reproduction of alleles is much greater in small populations than in large ones. When populations are very small, drift will predominate, and may preserve unfavorable alleles and eliminate favorable ones (this means purifying selection has a stronger effect in species with a larger effective population[22]). Weak selective effects may not be seen at all, as the small changes in frequency they would produce are overshadowed by drift.[23]In a large population, the probability of sampling error is small and little change to the allele frequencies is expected, even over many generations. Even weak selection forces acting upon an allele will push its frequency upwards or downwards (depending on whether the allele's influence is beneficial or harmful). However, in cases where the allele frequency is very small, drift can also overpower selectioneven in large populations. For example, while disadvantageous mutations are usually eliminated quickly in large populations, new advantageous mutations are almost as vulnerable to loss through genetic drift as are neutral mutations. It is not until the allele frequency for the advantageous mutation reaches a certain threshold that genetic drift will have little effect.[21]Most mutations have a clear negative selective effect and cause the gametes that they occur in to disappear after a few generations. It is possible to calculate how many percent of each generation will be removed by such mutations. The size of the remaining population, is said to be a factor f0, the equilibrium frequency of non-deleterious alleles, times the total population (f0 is between zero and one). When a neutral mutation spreads by drift in a population, some of the occurrencies will be removed because they are linked to such negative mutations. That is, they are located in chromosomes that are removed because of selection against a mutation in another part of the same chromosome. As a consequence, the effective population size is reduced by the factor f0. This means that mutation and selection in combination, causes the drift to have more effect. Because strength of genetic linkage varies along the chromosome, effective population size, and thereby genetic drift, also varies. With a higher recombination rate, linkage decreases and with it this local effect on drift.[24][25] This effect is visible in molecular data as a correlation between local recombination rate and genetic diversity,[26] and negative correlation between gene density and diversity at noncoding sites.[27]

Great! Then if you are familiar with these theories, then you are aware that today's population geneticists think that creationists are talking crap?

You even brought your own rope.
You actually quoted and highlighted your source saying: "When populations are very small, drift will predominate".This is just embarrassing. It's like watching someone hang himself in public.

Care to tell us what pop. gen. work he has published in the last 20 years? The only thing I can find that comes close, and not very close at that, is a comparison of different Raspberry cultivars.

Bear in mind that molecular genetics, i.e. the biolistic method of introducing genetic material, is not the same as population genetics.

I'm also not sure that what everyone else in this thread is talking about a lot is population genetics, in terms of long term patterns of ancestry it is mostly comparative genetics that is more relevant, although I understand that as sequencing technologies improve the 2 fields are converging to some extent.

The fact that someone more knowledgeable than you finds your gibberish downright embarrassing to read ... supports your position?Perhaps you could explain why. Or perhaps you could post more gibberish. Only time will tell, although I believe that I can guess.

You are, of course, wrong.

Ah, yes. So if Jimmy cracks corn, he's an expert on the subject of evolution.

Instead of blathering about how creationists have found one guy with equivocal qualifications who after "finding Jesus" started talking garbage --- why don't you put his garbage up for discussion?

In suggesting this, I am not seeking an unfair advantage, because goodness only knows how many genuinely eminent scientists I could quote saying that Sandford is talking crap.

This is just a restatement of the original statement that I questioned. Again, just how do you envision this happening? Yes, slightly deleterious alleles can become fixed in a population, but you go beyond Kimura and Ohta in claiming that deleterious genes must inevitably accumulate in populations to the point of making them less fit than prior generations. This is not a valid extrapolation of Kimura and Ohta.Here's why you're wrong:Imagine you have a population with slightly deleterious allele X that is not affected by natural selection and that eventually becomes fixed.Later slightly deleterious allele Y occurs in a different gene. It, too, is unaffected by natural selection, even in combination with allele X, and it, too, eventually becomes fixed in the population.Still later, slightly deleterious allele Z occurs in a different gene. It, too, is unaffected by natural selection, even in combination with alleles X and Y, and it, too, eventually becomes fixed in the population.This population can go on accumulating and fixating slightly deleterious alleles that are unaffected by natural selection even in combination with all the other deleterious alleles, and since there is no impact on natural selection then there cannot possibly be any impact on fitness.As soon as you introduce a slightly deleterious allele into the population that in combination with the older and now fixated deleterious alleles is subject to natural selection because it diminishes fitness, then that allele will be selected against. It will not spread through the population and cause the population to be less fit than prior generations.

So how many generations does it take for extinction?
300 generations?6,000 years?

Hi AOK,
Let's deal with your most serious error first:

Fitness is the primary criteria of natural selection.

Fitness and natural selection are extremely highly correlated.

You are so wrong and this is so fundamental that I can't imagine how you make sense of anything concerning evolution. You have a lot of rethinking to do.

It can be defined either with respect to a genotype or to a phenotype. In either case, it is equal to the average contribution to the gene pool of the next generation that is made by an average individual of the specified genotype or phenotype.

X, Y and Z are deleterious to such a slight extent that they are not subject to natural selection.

That means that an organism's fitness is not affected by whether they possess X, Y and Z in any combination.

Whether they possess any or all of these mutations or not makes no difference, the organisms have the same rate of survival to reproduce and are just as successful.

And if you instead argue that such slightly deleterious alleles are actually subject to natural selection, then they'll be selected against and will not spread through the population.

Each generation always has more mutations than previous generations, but the fitness will not decline because deleterious mutations are filtered out while beneficial mutations are retained.

I understand that you think that very slightly deleterious mutations can sneak in to a populations genome unnoticed by natural selection because they have a negligible impact on fitness, and you're not wrong about that, but as soon as these mutations accumulate in combinations where the impact on fitness is no longer negligible then natural selection will filter such combinations out.

We don't measure fitness relative to ancestral populations, because fitness is environment-dependent and the ancestral population is dead. The comparison is a necessarly invalid one - whose environment do you use? By definition the ancestral population has greater fitness in the ancestral environment, but conversely the modern population has greater fitness in the modern environment because the ancestral population has never lived there.Fitness is always a function of the organism's adaptation to its current environment, not to any environment in the past or future.

Relative fitness is quantified as the average number of surviving progeny of a particular genotype compared with average number of surviving progeny of competing genotypes after a single generation, i.e. one genotype is normalized at w = 1 and the fitnesses of other genotypes are measured with respect to that genotype. Relative fitness can therefore take any nonnegative value, including 0.

Absolutely incorrect. As your citation proves, neither scientists nor anybody else measure fitness as relative to ancestral populations.

The evolutionary mechanism causing the
fitness decline remains unknown. We suspect
that unintentional domestication selection and
relaxation of natural selection, due to artificially
modified and well-protected rearing environments
for hatchery fish, are probably occurring
(SOM text). Considering the mating scheme for
C[CxW] and the generation time for the fitness
decline, however, inbreeding depression
and accumulation of new mutations should not
affect these results. Regardless, our data demonstrate
how strong the effects can be and how
quickly they accumulate. To supplement declining
wild populations, therefore, repeat use of
captive-reared organisms for reproduction of
captive-reared progenies should be carefully
reconsidered.

In addition to your profound ignorance of population genetics, you're also displaying an utter inability to read statements written in plain English. Why is that? Are you hoping that if you spew enough bullshit, we'll all be baffled and simply surrender?Sorry, friend, I've seen far better bullshit. You'll have to try a lot harder.

How does one do this? Do we dig them up and reanimate them?

Decreasing compared to what? To other MODERN populations of fish? And what environment are they measuring this fitness in? In the hatchery environment where the hatchery fish have been selected for or in other environments where the other modern population has been evolving?

Fitness decline in which environment?

In this study, we investigated the strength
of genetic effects of domestication on the reproductive
success of captive-reared individuals in
the wild. Confounding environmental effects
were avoided by comparing captive-reared individuals
with different histories of captive breeding
in the previous generation (Fig. 1). We
reconstructed a three-generation pedigree of the
winter-run steelhead in the Hood River (19) and
compared adult-to-adult reproductive success
(number of wild-born, adult offspring per parent)
of two types of captive-reared fish (designated C):
captive-reared fish from two wild-born parents
(C[WxW]), and captive-reared fish from a wildborn
parent and a first-generation captive-reared
parent (C[CxW]). C[CxW] and C[WxW] were
born in the same year, reared in the same
hatchery without distinction, and released at the
same time. Both fish originated from the same
local population, so we can also exclude the influence
of local origin. The only difference between
them is half of the genome. The half
genome in C[CxW] was inherited from the
captive-reared parent and experienced captivity
for two consecutive generations (during the
egg-to-juvenile development). The other half
in C[CxW] was from the wild parent and experienced
captivity for one generation (C[CxW]
itself). In contrast, the entire genome of the
C[WxW] experienced captivity for one generation.
Thus, by comparing C[CxW] with C[WxW],
we were able to evaluate the effect of a single
extra generation of captive rearing on subsequent
reproductive success in the wild, while
controlling for the effect of rearing environment
(Fig. 1).