Common descent
The theory of descent, also called the theory of descent, is the scientific theory that states that all species go back to one or a few primordial forms as a common ancestor to which every living thing is connected in a straight line of descent.
According to the monophyletic (Greek: single-stemmed) theory of descent, all species go back to only one original species. Thus, any set of any living organisms always has only one most recent common ancestor and a successive series of other common ancestors. This is true of all living and ever-existing organisms on earth.
According to the polyphyletic (Greek: multi-stemmed) theory of descent, all present species go back to several basic stems.
The question of the mechanisms behind the emergence of species in this process is the subject of evolutionary theories. The question of the origin of the common ancestor is explored in natural science in the framework of chemical evolution.
The best known representative of the theory of descent was Charles Darwin.
The theory of descent explains the following essential facts:
- Similarities between blueprints of different animals that are descended from each other, e.g. the ancestry of the horse.
- rudimentary organs and atavisms
- Bridge forms (Archaeopteryx, coelacanth)
- fossils of extinct species
- genetics (in particular the broadest possible universality of the genetic code)
- Biochemistry (similarity of important molecules in related animal groups e.g. insulin, haemoglobin)
- Developmental biology, possible connection between ontogenesis and phylogenesis
A statistical study from 2010 has shown that life is very likely to have descended from a single ancestral species. A single common ancestor is 102,860 times more likely than several.
The ability of primitive organisms for horizontal (lateral) gene transfer opens up the possibility that instead of a single universal ancestor, a community of primitive unicellular organisms emerges, which, however, were in constant gene exchange with each other (common ancestral community), and therefore appear from today's perspective as one unit (species). At the beginning of life, vertical gene transfer (inheritance) had to be invented first (see RNA world hypothesis), while horizontal gene exchange was at the beginning with still incomplete separation of the cells.
Questions and Answers
Q: What is evolutionary biology?
A: Evolutionary biology is the study of how living organisms have evolved over time, and how they are related to each other.
Q: What did Charles Darwin propose in On the Origin of Species?
A: In On the Origin of Species, Charles Darwin proposed the theory of universal common descent through an evolutionary process. He believed that all living organisms on Earth were descended from a common ancestor.
Q: What is the last universal ancestor (LUA)?
A: The last universal ancestor (LUA), also known as the last universal common ancestor (LUCA), is the most recent common ancestor of all currently living organisms. It is believed to have appeared about 3.9 billion years ago.
Q: How does evolutionary biology support Charles Darwin's theory?
A: Evolutionary biology supports Charles Darwin's theory by providing evidence that all living organisms on Earth are descended from a common ancestor, and that this process occurred through an evolutionary process over time. This provides strong support for his hypothesis.
Q: What does it mean when a group of organisms have "common descent"?
A: When a group of organisms have "common descent", it means that they share a single common ancestor at some point in their evolution. This suggests that these species are related to each other in some way, and can trace their ancestry back to one source organism or species.
Q: How did Charles Darwin describe his view on life?
A: Charles Darwin described his view on life as having "grandeur", saying “There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one”
