Ontogenesis is the development of an individual being and differs from phylogenesis, which is known as tribal development. The concept of ontogenesis goes back to Ernst Haeckel. In modern psychology and medicine, both ontogenetic and phylogenetic considerations play a role.
What is ontogenesis?
Developmental biology and also modern medicine usually consider the development of living beings from the fertilized egg to the adult living being under the term ontogenesis. The term ontogenesis originates from Ernst Haeckel, who first used it in the 19th century. Meanwhile, ontogenesis is associated with the development of an individual being and is consequently opposed to phylogenesis. Ontogenesis deals with the history of structural change of a particular entity. In developmental psychology, ontogenesis stands for the psychological development of the individual. The biology understands by it analogously the individual development of the body and deals under this term with the development of an individual living being, which begins with the stage of the fertilized egg cell and ends with the adult living being. The embryo develops step by step organic attachments that become full organs. In each organ, cells are organized into tissues that differentiate and specialize.
Function and task
According to popular opinion, ontogenesis is closely related to phylogenesis and often makes its features visible. From basis of the Ontogenese thus conclusions can be drawn to the Phylogenese of living beings. For Ernst Haeckel this was the basic biogenetic law. To the Ontogenese belongs the beginning of the individual development. This beginning is localized for the Metazoa on the fertilized egg cell. The end of the development and thus of the Ontogenese is finally only the death of the living being. Multicellular organisms differ from unicellular organisms in this respect. The mother cell of unicellular organisms merges with the daughter cells during reproduction. Thus, unlike multicellular organisms, unicellular organisms potentially possess immortality. Without death as an end point, the ontogenesis of the individual living being still has a starting point, but no end. In the case of unicellular organisms, the ontogenetic consideration of the one living being from reproduction onwards thus overlaps with the ontogenetic consideration of the newly created living being. The development biology and also the modern medicine consider under the term of the Ontogenese mostly the living being development from the fertilized egg cell up to the adult living being. With the development of the individual being stages occur according to widespread assumption, which can be aligned with the development stages of the phylogenetic development. Thus, the phylogenetic developmental series are passed through in ontogeny by each individual of the species. This theory is controversial today. The ontogenetic consideration today includes mainly the consideration of cell differentiation in the embryo, which leads to the development of certain organs. The biological ontogenesis of multicellular organisms is now considered in terms of the stages of conception, blastogenesis, embryogenesis, fetogenesis, birth, infant stage, toddler stage, juvenile stage, pubescence and adolescence, and climacteric, senescence, and death. In psychology, the situation is different. Freud elaborated four phases for the development of the individual human being, which became a part of the teachings on infantile sexuality. After Freud, Granville Stanley Hall referred to the biogenetic basic law with his psychogenetic basic law, invoking ethnology, just as Haeckel invoked tribal history. Carl Gustav Jung used the term ontogenesis in connection with the individual and collective psyche. The latter was the inherited and supra-personal part of each individual soul and thus a product of phylogenesis, which everyone passes through, as it were, during ontogenesis. The upper parts of soul functions are to be distinguished from it and form the individual part of the soul, which can be perceived by becoming conscious of the personal unconscious. In psychology, however, ontogenesis can also correspond to the development or change of mental capacities and mental structures in the course of the individual life history.
Diseases and disorders
Psychology recognizes ontogenetic reduction, in the sense of tracing one’s condition back to events in one’s life history, as a psychotherapeutic method.For example, people respond to traumatic events in different ways. A traumatic event can cause pathological changes in the mental state and thus mental illness in one person on the basis of ontogenesis, while a second person does not react to the same event with the same changes in the psyche. Thus, ultimately, all mental illnesses manifest at an ontogenetic level and can hardly have phylogenetic origins. On the other hand, phylogenesis in the sense of humanly widespread developmental tendencies may favor certain diseases of the psyche. According to Haeckel’s original theory, conclusions about phylogenesis can be drawn on the basis of ontogenesis. Thus, in relation to ontogenetic disease developments, inferences could be drawn about the phylogenetically determined propensities of a species to certain diseases. Just as this conclusion might be valid for physiological diseases, it may also be valid for mental diseases. Modern pathology is concerned with both phylogenetic and ontogenetic considerations of particular diseases. If there is a phylogenetic basis for a certain disease, that disease automatically manifests itself ontogenetically more often than a disease without a phylogenetic basis.
