variation

HURDLE NUMBER 59. THE VARIATION HURDLE.

The following quote is from the book Darwin And His Flowers, by Mea Allan (In 1967 she was awarded the Leverhulme Research Scholarship to write about the botanists William Hooker and Joseph Dalton Hooker.), published by Faber and Faber, 1977, pages 122 to 123:- The author quotes Charles Darwin – “Does not Lyell (ie:- geologist Charles Lyell, Professor of Geology at King's College London in the 1830s.) give some argument about varieties being difficult to keep on account of pollen from other plants.” - - - - The author then tells us:- “The conclusion Darwin reached - - - was that transmutation of species had taken place when populations were isolated - - - and no longer able to prevent THE VARIATION NORMALLY KEPT IN CHECK BY BREEDING THROUGHOUT THE POULATION.” (My capitals.)

This next quote is from the book Purpose and Desire – What Makes Something “Alive” And Why Modern Darwinism Has Failed To Explain It, by J Scott Turner (Professor of Biology at the State University of New York), published by HarperOne, 2017, page 109:- “The problem for natural selection - - - was the unlikelihood that such strict control of a blood line (as enforced by animal breeders with selective breeding) could be sustained in nature. The problem is a statistical one. Imagine that a sport – a stallion with stripes – emerged in a population of wild horses - - - What sort of mate wouold our lucky striped stallion be likely to find? Most probably it would be a uniformly colored mare. Sports are, by definition, rare, making the “nonsports” or “wild types” abundant and more likely to be mating partners. Blending of their respective germ plasms would then produce offspring that, if they were striped at all, would be less distinctly so. If these dimly striped offspring managed to survive and mate, it would also likely be with other more abundant plain-colored horsed, further dimming the striping in their offspring. With every generation, - - - stripiness would be diluted more and more - - - the new trait would be “swamped.” Natural selection - - - - therefore could not work in a regime of blended inheritance.”

(My comment:- What this boils down to is that any variation in a species will be “kept in check” or removed because the animal possessing the variation is likely to breed with an animal that does NOT possess the variation, in which case the variation will become “diluted”, and over a few generations of “dilution” finally lost altogether. If a variation is to pass down the generations, then the animal possessing the variation must breed with another animal who also possesses that same variation, which is unlikely to happen. Then the progeny must also breed with animals possessing the same variation. A dog breeder can “enforce” selective breeding to maintain a particular variation, resulting in breeds of dogs that never appear in the wild state, because the variation would soon be “bred out” in the wild state. (In fact, when pedigree dogs are released into the wild, after a few generations, they have “bred out” the “variations”, and look more and more like wolves as the generations proceed.) The notion that this hurdle can be surmounted by small isolated populations encounters the following problem:- In a large population there is a good chance that more than one example of a particular variation exists in a cohort. In a small population, the chance of there being more than one example of a particular variation in a cohort is drastically reduced. I considered combining this “hurdle” with The Evolutionary Stasis Hurdle, because it helps to explain why Evolutionary Stasis is a constant feature of the geological record. However, I decided that it deserves a place as a separate hurdle.