XII.4.3 The transition from (inter)individual to inter-allelic selection may have been the basic prerequisite for the emergence of multicellular organisms with functionally differentiated tissues including germinal and somatic cell lines

The fact that the interests of the individual alleles became superior to the interests of individuals created the preconditions for the evolutionary emergence of various types of cooperation between individuals in the population.This category of cooperation includes, for example, ethological patterns of pseudoaltruistic behaviour (see IV.4.8.2.1), i.e. patterns of behavior through which an individual increases the chance of survival of genetically identical individuals formed by asexual reproduction, at the expense of its own reproduction (Dawkins 1976).However, it is quite possible that a very similar explanation can also be applied to the formation of multicellular organisms, to be exact in explaining the differentiation of lines of somatic and germinal cells within a biological individual.Somatic cells do not pass their genes on to future generations, but can fundamentally affect the degree and the probability with which copies of their genes will be passed on to future generations through genetically identical germinal cells.If amphimixis did not occur, cells would pass the genome on to the next generation in unaltered form, i.e. basically like a single universal gene controlling all the properties of the future organism.In this case, constant selection pressure would act on fixation of mutations capable of increasing the probability that the cell in which they are located would begin to act as a germinal cell and would cease to act as a somatic cell – even if this leads to a reduction in the fitness of the particular organism.All the genes in the cell would be engaged in this result and would cooperate with the mutated allele.In contrast, in organisms with amphimixis, in the subsequent generations the individual genes will find themselves next to other alleles of the originally mutated gene and will not participate in the advantage that the particular mutation provides.Thus, groups of alleles in the genome of a certain somatic cell cannot “organize a conspiracy” against the interests of the other alleles and against the interests of the multicellular individual.To the contrary, all the alleles in all the loci will share a joint interest in creating the most effective mechanisms that would prevent the spreading of mutations permitting the passage of cells from the somatic line to the germinal line.The integrity and thus also the fitness of the organism will consequently not be consistently endangered by selection “penalization” of “loyal” alleles, i.e. alleles that participate in the ability of a multicellular organism to control, during ontogenesis, the division of cells into somatic and germinal lines in the optimal manner from the viewpoint of the fitness of a multicellular organism.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.