6. The Heritages of the Chordate Phylum

6.0 Introduction

Homo sapiens sapiens is characterized by several attributes that were needed together for the attainment of an evolutive level superior to that of other primates. The chances for the phylum of the chordates to fulfil its potentialities and reach human consciousness were remote: had the scorpions not been such terrible predators, there might have been no need for the development of a cephalic shield by the first chordates, and hence ultimately no skull. Among the fishes, only the crossopterygians possessed the attributes useful for a passage to dry land. Once on dry land, only that amphibian group which adopted a dry keratinous skin and oxygenation through lungs alone, was successful. Mammals superseded dinosaurs only because a short warm burst that took place at the end of the Mesozoic era provoked the disappearance of the dinosaurs. In the mean time, angiospermic plants became successful, on which insects could feed. These, in turn, were edible by insectivorous mammals, which barely managed to survive during the dinosaurian dominance. Among mammals, the primordial condition for further evolutive progresses was the device of a system of intrauterine embryonic growth. The mammals, and these alone among all animal classes, evolved a group where the embryo remains within the mother’s womb – being part of the mother’s body – for a long time after fecundation. Vivipariness is known to exist, e.g. among fishes, but this is not comparable with the intimate relationship of embryo and mother via a placenta.

Child bearing required a considerable adaptation of the immunological defences of the gravid mother. It allowed the development of the offspring’s central nervous system in a protected environment until it was sufficiently developed to permit a fully aquatic or arboreal life. An arboreal life can be successful only if the adequate ramified trees are at hand but also requires on the part of the animal group making such a step, the ability to adequately solve spatial and visual problems. The capacity to solve such problems was acquired by vertebrates only very late in the course of evolution. Sunspots, the proximity of a moon, ice ages, meteorites, volcanic activity, plate tectonics and dry lands all contributed to force the issue. Other phyla went through the same events but did not respond in the same way.

The phyletic line of the hominids is a privileged convergent line that, through rapid adaptive changes, exploited all the predispositions at hand to devise a system of transfer of information that resulted in turn in the attainment of a new evolutive level. A lengthening of individual lives and a development of the sense of individuality that made obsolete the concept of species seen as a privileged system of transfer of information through sexual exchange accompanied this.

Two intertwined evolutive trends within the chordate phylum are remarkable. The first is the trend to individualization of each member of a species. The immune system, hormones and the nervous system that developed along lines different from those taken by other animal phyla achieve this individualization. The second is the development of the brain to such a point that a level of cognition was reached where conscience, morality and mental life acceded to a unique level of spirituality.

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