Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

Rates of anagenetic changes

Taxonomic systems employed in the past or at the present can be classified as artificial systems and natural systems. In creating artificial systems, systematists attempted to classify organisms for practical and didactic purposes. As long as only a few species were known, systematists tried basically to create, not a generally valid system, in which it would be possible to also classify newly discovered organisms, but rather a determination scheme that would make it possible to differentiate the members of the individual known species. Only with an increasing number of discovery voyages and the recognition of the enormous biodiversity in newly discovered countries did it become apparent that there are fundamental differences between the determination scheme and the taxonomic system.
Some artificial systems classified organisms on the basis of various combinations of a small number of, where possible, universally occurring traits, while others used a great many traits for classification, where the groups of these traits could differ from one taxon to another. An artificial system based primarily on the basic cell shape and affinity for certain dyes was used until recently for classification of bacteria. Even today, artificial systems remain a basis for the creation of determination keys (determination schemes) for the individual groups of organisms. Their closed nature is a great disadvantage. An artificial system only allows classification of organisms that were known at the time of creation of the particular system. As soon as a new species appears, its proper assignment need not be possible in the majority of cases. An originally unknown species would either be classified under some other species or a suitable category would be lacking in the system. Another great disadvantage of artificial systems lies in their subjectivity. A single group of organisms can be classified on the basis of other traits into a completely different system of taxa, where the selection of traits is a matter of the subjective decision of the systematist.
Natural systems attempt, not only to meaningfully classify organisms for practical and didactic purposes, but also, in creation of the individual taxa, to reveal and especially respect the natural, objectively existing relationships amongst the created taxa. The natural system has three basic advantages. Primarily, the natural system is open, which permits it to be used to also classify species that were not yet known at the time when the system was created. The second advantage lies in the fact that, if there is actually, objectively a natural system of organisms, then its discovery should not be dependent on the subjective selection of traits and procedures of systematists. Systems created by individual systematists using various methods and employing various traits should gradually approach one another as knowledge is steadily accumulated and skills acquired. The third advantage of the natural system is its predictive potential. While an artificial system allows only description of the distribution of the traits on the basis of which the particular system was created, a natural system should also enable prediction of the distribution of those traits that were not used for classification of the organisms or that were not known at the time of creation of the system.

see History of evolutionism – classical Darwinist period

See goal-orientation.

Theory of frozen plasticity– see Frozen plasticity Theory

see Darwin

As molecular biological data gradually accumulated, it began to be clear that some important evolutionary processes occur beyond the direct influence of selection. Molecular biological techniques enabled study of these evolutionary processes. As a consequence, the relevant areas gradually began to penetrate into textbooks on evolutionary biology and thus into the general consciousness of biologists. Neutral evolution was the first to become an object of the interest of evolutionary biologists, i.e. evolution occurring as a consequence of genetic drift. Sewall Wright was the first to study the aspect of random fixation of selectionally neutral traits. However, molecular biology was the first to demonstrate what an important biological phenomenon this actually is. All indications suggest that incomparably more traits become fixed in evolution through genetic drift than through selection. It is true that the most interesting traits, i.e. adaptive structures, are fixed exclusively through natural selection. On the other hand, genetic drift can be of fundamental importance in the formation of biological diversity and possibly also in speciation. The Japanese biologist and geneticist, Motoo Kimura (1924–1994), made the greatest contribution to elaboration of the theory of neutral evolution. It was found in the study of molecular evolution that interactions of drift with selection are of great importance in the evolution of molecular traits. At the present time, this extensive area is the subject of the theory of “almost neutral evolution” (Ohta 1993; Ohta 1996)) and also the theory of genetic draft (Gillespie 2000; Gillespie 2001)).

            Evolutionary drives are another important mechanism that was discovered in direct connection with the development of molecular biology. Research has shown that some alleles are fixed in the population, not because they increase the chances of survival of their bearers in competition with other individuals, but because they are capable of preferentially spreading in the genome of an individual and amongst sexually reproducing organisms, as well as in the gene pool of the population, at the expense of other alleles. Molecular drive was described by Dover (Dover 1986); other types of evolutionary drives have been studied within the context of individual, mostly narrowly oriented studies by a number of authors {5957, 435, 3200, 4530, 8645}, so it is difficult to designate specific persons as the authors of the particular concepts.

Darwin

see Darwin

From the point of view of evolution of behavior, it is very important that the same individuals repeatedly come into mutual interactions. These individuals are able to adjust their behavior according to the response to the behavior in the past and, at the same time, they have to expect that their behavior will influence the future behavior of a partner (opponent). In this case, even in the prisoner’s dilemma game, a number of strategies exist that are far more advantageous (and friendly) than the always betray strategy. Among the first recognized and yet relatively most successful strategies is the "Tit for Tat" strategy (Axelrod & Hamilton 1981). It always begins with cooperation and in every next step the individual repeats the opponent’s strategy in the last step. If two individuals following this strategy meet, they can, in the long-term, profit from mutual cooperation while, if they meet an opponent who follows the always betray strategy, they lose in the first step but in the next ones they give the chronic betrayers no advantage. In the overall balance, the simple Tit for Tat strategy wins.

             The above-mentioned conclusions are valid only under one vitally important condition: neither opponent is not allowed to know when their interactions will finish, i.e. how many steps (moves) are left in the game. As soon as it would be obvious that the game is ending and the opponents would know they are not going to meet in the future, for any of them the most advantageous thing to do would be to betray in the last step and get the extra reward for one-sided betrayal. So the last step would be determined and immediately the question would arise as to how to act in the previous move – the most advantageous solution would be betrayal again. From the beginning, the game would be about who will be the first to betray. The situation is completely different when the players do not know which step will be the last, which is much more favorable for spreading of cooperative game strategies.

An analogy of the prisoner’s dilemma game is used in situations when an individual who follows its own goal against a large group of players, e.g. against a whole society. In this case, the behavior of all the participants will end up in a situation called the “Tragedy of Commons” (Hardin 1968). The course and result of this game were very graphically described using the example of the fate of English country commons, the pastures open to all. If a village’s commons were not regulated as to how intensively they could be pastured, they were completely destroyed by immoderate pasturing and the cattle of villagers, which were dependent on the commons, died of hunger. If the commons were divided among villagers, each could only have as many animals as his pasture would be able to feed. In the commons case, the most advantageous strategy for each individual was to get as many animals as possible as soon as possible; before someone else’s animals would destroy the pasture and without – moreover - losing out against other herdsman until complete devastation of the commons occurred.

see Crossing valleys in the adaptive landscape

Transversion – see Point mutations

The Trivers-Willard model describes the behavior of an organism in a situation where the external conditions permit determination in advance of whether sons or daughters will have greater fitness (Trivers & Willard 1973). Under these conditions, it is advantageous for an individual if it is capable of adapting to the momentary conditions and can produce individuals of a single particular sex.

            The situation amongst parasitic hymenopterous insects can serve as an example (King 1994). A simple mechanism exists in hymenopterous, haplodiploid insects, which can determine in a female whether an egg should develop into a male or female. Males are haploid and are hatched from unfertilized eggs, while females are diploid and hatch from fertilized eggs. Because, following copulation, females store the male sperm in their spermatheca, sometimes for the rest of their lives, rotation of the egg in the oviduct can determine whether it is fertilized or not and whether it will produce a female or a male. For example, the larvae of parasitic wasps of the genus Nasonia parasitize on the larvae of grain-eating insects, so that the amount of nutrients that they have available during their development and thus the size to which they grow and will also have as adults can be estimated in advance according to the size of the grain into which the female lays its eggs. If the grain is small, the grain-eating larvae inside will also be small and the future larvae and adults of the parasitic wasp will not grow to the required size. This is a handicap for females, as the number of eggs produced during its lifetime is directly proportional to its size. In contrast, even a small male is capable of producing more than enough sperm to fertilize every female that it encounters during its lifetime. Thus, it is advantageous for a female to lay unfertilized eggs in small grains and fertilized eggs in large grains.

            In diploid organisms with heterogametic male sex, the sex of the embryo is determined by the sex chromosome brought into the zygote by the male gamete. Thus, it might seem that the female has rather limited means of influencing the sex of her progeny. However, even here, appropriate mechanisms can exist, consisting, for example, in separation of sperm with chromosome X or Y, or possibly the possibility of selectively killing zygotes, embryos or, in the extreme case, young of a certain sex (Komdeur et al. 1997; Mendl et al. 1995). The effectiveness of such mechanisms in humans is reflected, for example, by a secondary sex ratio close to a value of 5 (in favor of males) in some areas of India and Pakistan (Judson 1994).

            Shifting of the sex ratio in humans in dependence on the physiological condition of the mother apparently also occurs by natural means. For example, it has been observed that, if a mother gives birth to a girl with low birth weight (under 3.2 kg) in her first pregnancy, it is more probable that the next child will also be a girl (64%). If the first-born girl was heavier than 3.2 kg, the probability that another girl will be born is lower (33%) (Pawlowski & Cieplak 2002). Similarly, it has been observed that women with latent toxoplasmosis (approximately one quarter of women of fertile age in the population under study) have several dozen percent greater chance of giving birth to a boy than a girl (Fig. XIV.7) {12801, 13715}. It is possible that the partial immunosuppression induced by the parasite means that a greater percentage of male zygotes survive in the female organism (in general, male zygotes induce a greater immune response than female zygotes), as a consequence of which the secondary sex ratio in women infected with toxoplasmosis is much closer to the primary sex ratio (ratio of male and female zygotes immediately after fertilization of the egg).

            In some animals, specifically in a number of species of birds and mammals including humans, the female can react, not only to the external factors in the environment, for example the amount of food available, but also, for example, to her social position in the flock or herd. Because the social position of the parents can substantially affect, either genetically or nongenetically, the social position of the progeny, it is advantageous for the parents if they are capable of adapting the sex of their progeny to their social position. In most societies, if they hold a low social position, it is more advantageous for them to produce daughters, as even females with a low social position are usually able to reproduce. On the other hand, if the parents hold a high social position, it is evolutionarily more advantageous for them to produce sons. In a great many species, males with higher social position become the fathers of most of the young in the population. This phenomenon has, of course, also been studied in humans but the results are so far not entirely unambiguous (Chahnazarin 2003). In any case, the substantially greater number of sons in the descendants of the European aristocrats, American presidents or American generals (Mueller & Mazur 1998), or in women who were in the care of more expensive gynecologists {12801} is a fact for which it is rather difficult to find an alternative explanation.  The results of an extensive study performed on data derived from pre-industrial Scandinavia suggest a possibility. In contrast to the number of daughters, the number of sons is negatively correlated with the length of the life of the mother (every son meant shortening of the mother’s life by 34 weeks). This suggests that “bringing up” sons is more demanding on the maternal organism than “bringing up” daughters and only women in good condition with sufficient material security can allow themselves to invest their reproduction potential into sons {10869}.

The emergence of sexual reproduction leads to sexual dimorphism – differentiation of individuals of a single species into males and females. Simple considerations indicate that an individual that would produce only asexually reproducing progeny (parthenogenetic female) would reproduced twice as fast, expending the same amount of energy, as an individual that would “squander” half its reproduction efforts in the production of males (Fig. XIII.1). This effect of sexual reproduction is generally denoted as the two-fold ecological costs of sex (the cost of males) (Maynard Smith 1978). The two-fold ecological cost of sex is, of course, not applicable to hermaphrodites which, during mating, exchange sex cells, to unicellular organisms, to organisms with external fertilization that produce male and female cells of the same size (isogametes) or to organisms where both parents must care for the young with comparable intensity. However, the two-fold ecological cost of sex does not apply even in a situation where reproduction of individuals in the population is limited by unfavourable external factors. It cannot be excluded that this could be the reason why, in species capable of both sexual and asexual reproduction, i.e. in species with facultative sexual reproduction, sexual reproduction usually occurs under circumstances where the population finds itself in unfavourable conditions (Burt 2000).

see Scientific nomenclature