Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The Origin of Speciation
The modern synthesis offers a powerful paradigm for the evolution of life, but looks still inadequate to explain the origin of species. The problem is that it is very difficult to create a new animal. New traits must be assembled in such a way that they allow the organism to survive at least a few generations. The new traits must stabilize. The mutating individuals must avoid being rapidly re-assimilated into the original species through interbreeding. And, last but not least, both sexes must arise at the same time.
Darwin did not solve the mystery of the origin of species, despite the fact that he titled his book that way. Only after the advent of genetics, and mainly thanks to the work of the German zoologist Ernst Mayr, were biologists able to advance hypotheses. If a population splits in two because of whatever accident, both random mutations and environmental differences (natural selection) will cause the two groups to evolve differently until they become two separate species. If the two groups ever meet again, they are more likely to compete than to interbreed, as any species that have similar behavior in the same territory.
Today, there is consensus that species are born (at least) from geographic isolation of a population, but then it is not clear what biological mechanism originates hybrid infertility (this population cannot inbreed with other populations anymore) and fertile diploids (this population has both male and female that can breed).
It is not clear whether the same sudden discontinuity at the level of the phenotype (the organism) occurs as well at the level of the genotype (its genome). We know that the genotype is not the same for every member of a species, that small changes occur all the time. It may well be that changes can accumulate for a long period of time without any visible consequence on the phenotype while they are reaching a crisis point. At that point of genetic “drift”, the smallest change in the genotype may have catastrophic consequences for the phenotype.
In the opinion of Harold Morowitz, this is the way organisms acquire new levels of organization, the way they evolve towards more and more complexity. All of a sudden a “gateway” opens up that leads to a whole new range of possibilities. For example, a glue that can hold cells together may be responsible for the sudden appearance of multicellular organisms which in turn quickly acquired a completely new behavior.
The US linguist Philip Lieberman believes in “functional branch-points”. He recalls two principles. The first principle is that natural selection acts on individuals who each vary: species that successfully change and adapt are able to maintain a stock of varied traits coded in the genes of the individuals who make up their population. The second principle is the "mosaic" principle, which holds that parts of the body of an organism are governed by independent genes. There are no central genes that control the overall assembly of the body. Given these principles, a series of small, gradual changes in structure can lead to an abrupt change in the behavior of the organism; and an abrupt change in behavior may cause an abrupt change in morphology which causes the formation of a new species. New species are formed at "functional branch-points".
By surveying “adaptive radiation” (the spread of species of common ancestry into different niches) and “evolutionary convergence” (the occupation of the same niche by outcomes of different adaptive radiation), the US biologist Edward-Osborne Wilson argued that opportunity is likely to cause an explosion of species formation.
The problem is that the genetic mechanism that fosters variation is not well understood. Several researchers have observed that bacterial cells tend to choose for themselves advantageous mutations over harmful mutations. Darwinism and modern genetics, instead, prescribe that mutations must be absolutely random. One possible explanation that is not in conflict with Darwinism is that, under conditions of stress, cells generate many more mutations than they would normally do, and of these mutations the most advantageous survive and are observed. If confirmed, this would imply that cells know when the survival of their species is in jeopardy and enter a state of frenzy in which they produce as many mutations as possible, hoping that at least one will be able to adapt and resolve the stress. Natural selection is certainly a weak process for evolving species, but it would be far more effective if it turns out that it is coupled with another process which is capable of generating a lot of diversity every time evolution is desirable because of environmental pressure.
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