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

All the species existing on the Earth at a given moment have behind them a line of ancestors of identical length, as they were apparently all formed by gradual branching off from a single common ancestor.Consequently, it does not make sense to differentiate species into evolutionarily old and evolutionarily young, unless we are referring only to the actual length of existence of the particular species.Similarly, it is difficult to differentiate the individual evolutionary lines as evolutionarily old and young.The situation is somewhat different with taxa, as they are mostly defined in modern systems on the basis of an attained level of anagenesis.Every evolutionary novelty emerged at a certain moment in phylogenesis and, together with it, the relevant taxon was also de facto formed.Of course, de jure, a taxon was formed when a taxonomist defined it separately from other taxa; in this sense, the differences in the ages of taxa are really negligible on an evolutionary time scale.The ages of the individual taxa existing at a certain moment thus vary substantially and consequently it makes sense to speak of old and young taxa.However, this could lead us to begin to speak of evolutionarily primitive and evolutionarily advanced or even evolutionarily higher and evolutionarily lower taxa.Darwin was already aware of the pointlessness of classifying organisms as higher and lower.Evolution is not directed towards some predetermined result.Thus, it is not possible to determine how far the individual taxa have reached on some common evolutionary scale.All evaluations in this sense are thus entirely subjective and are mostly based on our anthropocentric view of the world.The more similar an organism is to humans, the evolutionarily higher it seems to us.It is obvious that, if a similar evaluation were to be performed by a squid or a sequoia, they would arrive at quite different results when classifying organisms as higher and lower than, for example, A. Portmann on the basis of study of the level of encephalization amongst the members of various taxa (Portmann 1960).

            The classification of organisms as evolutionarily primitive and evolutionarily advanced apparently makes somewhat more sense than their classification as lower and higher organisms.In a phylogenetic line, it is possible to recognize which species branched off from a common ancestor sooner and which later.By comparing the phenotype traits of the individual species, the polarity of the individual anagenetic changes can be determined and thus it is possible to say in which species more primitive (in the sense of ancestral) forms of traits predominate and in which derived forms tend to be more common.Once again, however, it must be borne in mind that that an evolutionarily younger form of a trait need not be the best form from a functional viewpoint.Which species will tend to undergo speciation and which extinction is also determined by their adaptation to the environment; however, species selection is decisive and can select traits on the basis of quite different criteria.In addition, the element of chance is very important here.The survival of a species is mostly not determined by its evolutionary adaptation to the prevalent natural conditions, but rather by fortunate chance, specifically the presence of pre-adaptations that enable the species to come to terms with an environmental change for which it was not selectionally adapted (see XXII.2).

            It is not clear whether modern species are better adapted to their environment than primitive species and it is even more disputable whether it is even possible to find a suitable measure of perfection of adaptation in organisms that evolve, not only at different rates, but also in different directions.The fact that primitive and evolutionarily advanced taxa have been preserved to the present time indicates that they do not differ much in this respect.In any case, it must be emphasized that the rates of evolution of the individual traits, for example individual organ systems, need not be in any way correlated.A taxon can be highly advanced evolutionarily with a highly functional organ or certain organ system and can simultaneously be very primitive, both from the evolutionary point of view and functionally, in its organs or in other organ systems.Thus, the members of any taxon are a sort of mosaic of evolutionarily primitive and evolutionarily advanced traits.