Many have encountered such a concept as biogenetic laws of development, but few can explain their meaning. Now this term is rarely used due to criticism of modern scientists. What is the essence of biogenetic law? Briefly, this concept can be described as follows: every living organism in its development passes to a certain extent the same stages as its ancestors.
The biogenetic law was first formulated by Charles Darwin in his famous work The Origin of Species, published in 1859. However, his wording was rather vague. Ernst Haeckel, a famous German scientist who introduced terms such as ontogeny, ecology, phylogeny and some others, as well as his famous theory of the origin of multicellular organisms, gave a clearer definition of the concept of the biogenetic law of development.
The formulation of Haeckel said that the ontogeny of the organism is a repetition of phylogenesis, that is, the historical development of organisms of the same species. Biogenetic law for a long time was called "Haeckel's law", as a tribute to a brilliant scientist.
Regardless of Haeckel, another German naturalist, Fritz Müller, formulated his own definition of biogenetic law in 1864.
Relationship with evolutionary theory
A modified definition of biogenetic law, according to which one species can acquire signs of a species that existed earlier, confirms the evolutionary theory. Because of the reduction in the stages of ontogenesis and arhallaxis, the organism acquires some features peculiar to its long-standing ancestors, but it can not acquire all characteristic features of them. This confirms the second law of thermodynamics for living organisms (the impossibility of spontaneous reduction of entropy in an open system) and the law of irreversibility of evolutionary processes (restoration of features lost during the evolutionary process is impossible).
The biogenetic law, in the form in which Ernst Haeckel formulated it, has been severely criticized by researchers. Most scientists found the arguments of the colleague to be unprovable. At the end of the 19th century, when researchers wanted to know what the biogenetic law was, they discovered some contradictions and inconsistencies in the truth. From observations and experiments it became clear that ontogeny is not complete, but only partly repeats the stages of phylogenesis. An example of this is the phenomenon of neoteny - a reduction in ontogeny and loss of its individual stages. Neotenia is characteristic of amphibians - axolotls, which, due to individual hormonal characteristics, reach sexual maturity at the stage of the larva.
The concept, the reverse of neoteny, - anabolia, - is defined as the elongation of ontogeny, the appearance of additional stages in the development of the organism. With this form of ontogeny, the embryo actually passes through the same stages of development as its adult ancestors. However, with anabolia, it is possible that at the late stage of development, ontogeny does not go the other way, and the organism does not acquire definite differences from the adults of its species. That is, a complete repetition of all stages of development of ancestors of the same species is impossible, since the ontogeny of the organism occurs under the influence of various factors (environmental impact, spontaneous mutations in the genome), and not only through the realization of genetic material.
Russian biologist A. Severtsov introduced the term arhallaxis - a change in ontogeny, in which the earliest stages of the development of the body differ from the phylogeny of its ancestors. Obviously, recapitulation (repetition) of features characteristic of adult individuals of the same species is impossible, and the body acquires new features that were not characteristic of its appearance before.
From a number of scientific studies it became clear that the biogenetic law formulated by Haeckel has many exceptions and contradictions. The scientist was sure that ontogeny completely repeats phylogeny. This was his mistake. In fact, phylogeny is formed from a number of ontogenes of representatives of a certain species, and not vice versa. Now the term "biogenetic law" is not used in scientific literature.