Descent theory
The theory of descent , also known as the theory of descent , is the scientific theory that says that all species go back to one or a few archetypes as a common predecessor, with which every living being is connected in a straight line of descent.
According to the monophyletic (Greek: one-stemmed) doctrine of descent, all species go back to just one primordial species. Any number of any living organisms therefore always has only one youngest common ancestor and a successive series of other common ancestors. This applies to all living and ever-existing organisms on earth.
According to the polyphyletic (Greek: multi-stemmed) doctrine of descent, all current species go back to several basic stems.
The question of the mechanisms behind the origin of species in this process is the subject of evolution theories . The question of the origin of the common predecessor is researched in natural science within the framework of chemical evolution .
The best known proponent of the descent theory was Charles Darwin .
The theory of descent explains the following essential facts:
- Similarities between blueprints of different animals derived from one another, e.g. B. the ancestry of the horse .
- rudimentary organs and atavisms
- Bridge shapes ( Archeopteryx , Coelacanth )
- Fossils of extinct species
- Genetics (especially the broadest universality of the genetic code )
- Biochemistry (similarity of important molecules in related groups of animals e.g. insulin , hemoglobin )
- Developmental biology , possible connection between ontogeny and phylogeny
A statistical study from 2010 showed that life is very likely to have descended from a single primal species. A single common ancestor is 10 2,860 times more likely than several.
The ability of primitive living beings for horizontal (lateral) gene transfer opens up the possibility that instead of a single universal ancestor, a community of primitive unicellular organisms, which, however, were in constant gene exchange with one another ( common ancestral community ), and therefore from today's point of view as a unit (species ) appear. At the beginning of life, vertical gene transfer (inheritance) had to be invented (see RNA world hypothesis ), while horizontal gene exchange was at the beginning when the cells were still incomplete.
literature
- Schischkoff: Philosophical Dictionary. 22nd edition. 1991, ISBN 3-520-01322-3 , Theory of Origin
- Rainbow, Meyer: Dictionary of Philosophical Terms. 2005, ancestry theory
Web links
Individual evidence
- ^ A formal test of the theory of universal common ancestry: Nature: Nature Publishing Group . www.nature.com. Retrieved January 15, 2011.
- ^ All Present-day Life Arose From A Single Ancestor - Science News . www.sciencenews.org. Retrieved January 15, 2011.
- ^ Geoffrey M Cooper: The Origin and Evolution of Cells , in: NCBI 2000.