Mutations and natural selection in giraffes (revisited)
October 26, 2013 | James Kohl
Excerpt: “The two fundamental principles of evolution are mutation and natural selection.” Evolution, Games, and God: The Principle of Cooperation (p. 210)
My comment: We see similar statements consistently used in failed attempts to explain anything at all about evolution. That’s why addressed the nonsense of the statement above in an earlier blog post. In ‘Natural cooperation’ is nutrient dependent and pheromone controlled, I wrote, “Natural cooperation in deer would be exemplified if there were two deer in this picture and one deer was helping another reach leaves that were higher up in the tree, or helping to carry leaves back to their ‘nest’. With a picture like that, we could place mutations theory in the context of natural selection for nutrients in ants, in the context of natural cooperation, and in the context of the metabolism of nutrients to species-specific pheromones that control reproduction. Without a picture of one deer helping another to acquire nutrients, we are left with the concept that deer might somehow mutate and become like giraffes that have adaptively evolved to acquire nutrients from taller trees.”
The idea that “…deer might somehow mutate and become like giraffes that have adaptively evolved to acquire nutrients from taller trees” has been dropped in the latest article about the ecologically-based evolution of differences in giraffes. See the news report: “They found that regional differences in the timing of precipitation, and the resulting increase in local vegetation and plants (“greening”), could best explain the source of genetic differences. Each species seems to be tied to their local seasonal cycle of greening, which is markedly different among species, suggesting that annual climate cycles may help maintain genetic and phenotypic divergence in giraffes.” See also the journal article: Regional Differences in Seasonal Timing of Rainfall Discriminate between Genetically Distinct East African Giraffe Taxa.
Differences in species of giraffes are now tentatively supposed to be due to visual input. “In our hypothesis of ecologically mediated maintenance of population divergence, differences in reproductive timing need not act alone. For instance, mate recognition mechanisms may also contribute to isolation. In this context, differences in pelage pattern may serve as visual cues in mate choice, possibly through imprinting on the conspecific pelage pattern during the early stages of life .”
Pelage is “The coat of a mammal, consisting of hair, fur, wool, or other soft covering, as distinct from bare skin.” It is important to note that the authors of the latest article on speciation in giraffes add: “However, to our knowledge no field data exist on the use of pelage patterns in mate recognition.” If you have followed the argument so far, you realize that mutation and natural selection (i.e., the two fundamental principles of evolution) have just dissapeared from the explanation of mate choice in giraffes for pelage differences. Thus, despite no evidence that visual cues are involved in speciation, the concept of mutation-driven evolution in giraffes is gone.
Where did that ridiculous concept go, and why weren’t we told where it went? I think that researchers today are reluctant to even mention the concept of mutation-driven evolution because they know how ridiculous it sounds to an educated audience. But, without a theory to substitute, these researchers are left only with an unsupported claim that “…differences in pelage pattern may serve as visual cues in mate choice…” That claim is equally ridiculous, but would fit best with the context of visual cues being responsible for the evolution of long necks in giraffes, which was formerly attributed to mutations and natural selection.
Clearly, the model of nutrient-dependent pheromone-controlled adaptive evolution presents a problem for anyone who claims that visual cues may be responsible for mate choice, whether in giraffes or any other species. For example: Diet alters species recognition in juvenile toads.
These authors attest to the fact that: “Regardless of mechanism, our results suggest that diet could affect the ontogeny of species recognition.” They also suggest that: “Early experience during critical developmental periods could generate long-lasting effects on species recognition, resulting in stable lifetime preferences within individuals but striking variation among individuals (mimicking a genetic polymorphism). Alternatively, an individual’s contemporary environment could affect its immediate expression of species recognition, such that the degree to which an individual preferentially associates with conspecifics (and, therefore, hybridization) becomes closely tied to environmental stochasticity.”
Since there is no evidence to suggest that mutation-initiated natural selection for visual cues is responsible for mate choice in any species from microbes to man, recent reports from the study of speciation in toads and the study of speciation in giraffes seem to attest to the fact that speciation is nutrient-dependent and pheromone-controlled as it appears to be in all species.