Without evolution there is no life
“Nothing in biology makes sense except in the light of evolution.” This is the famous title of an article by Teodosi Dobžanski from 1973. In the article, the Russian-American evolutionary biologist describes evolution as the means by which God created life and created the earth. But what exactly is evolution?
In biology, evolution is defined as the gradual change of hereditary traits from generation to generation. So when an originally hairless species of rhinoceros develops a protective coat during an ice age, that’s evolution. Even if new variants of the corona virus keep appearing, it is called evolution.
Evolution occurs only when there is selection among the characteristics of a group of organisms. In this process, also known as natural selection, characteristics are passed on to the next generation with varying frequency: some become more common, others become rarer or disappear.
Thus, selection is the driving force of evolution. In order for the election to be made, the following conditions must be met:
- The characteristic must exist in different variants.
- The characteristic must be hereditary.
- Different manifestations of a trait must lead to differences in fitness.
British naturalists Charles Darwin and Alfred Wallace discovered these fundamental principles of evolution. They explain the enormous diversity of life on earth: individuals with different characteristics compete with each other for scarce resources and pass their characteristics on to offspring. As a result, individuals constantly adapt to new environmental conditions and thus produce a wide variety of forms and survival strategies.
An incredibly simple principle for such an incredibly diverse phenomenon as life!
Evolution – just a theory?
When researchers draw conclusions from their research, they are called a hypothesis or theory. The “theory of evolution” is therefore not a purely hypothetical assumption, but was based on measurements and observations from the very beginning. Today, evolution can be simulated and examined in the laboratory. Today, it is a scientifically recognized fact that life on Earth developed according to the principles of evolution.
Organisms on Earth pass on their traits through their genetic makeup. All the information necessary for an individual’s function is stored in his DNA. In addition, there are chemical changes in the DNA molecule. Thanks to these so-called epigenetic changes, the organism can also pass on the traits it acquired during its life to its offspring.
For evolution to take place, the genome and/or epigenome must be modified. Such changes are called mutations. Changes in DNA occur more or less randomly as a result of environmental influences such as radiation or mutagenic substances. Even when cells divide and duplicate their DNA so they can distribute it to their daughter cells, copying errors can occur, creating new variants for evolution.
Max Planck researchers have discovered that some regions of DNA are better protected against mutations and why this is so. In this way, the cell repair machinery protects particularly important genes from potentially harmful changes. This discovery contradicts the prevailing dogma that mutations do not occur with the same frequency in important and less important genes – that is, they are not evenly distributed.
From start to finish
Thus, evolution has been taking place on Earth since, several billion years ago, molecules capable of reproduction first appeared and could pass on their properties and variants to the next generation. Many researchers now assume that RNA molecules were the first to be copied and duplicated. It is still not known how the first cells were formed. Tiny droplets of fat, which offered RNA molecules a protected space to react, may have played a role. Hot springs or freshwater pools could have provided suitable living conditions for this on early Earth.
During millions of years, life adapted to different environmental conditions in new stages of development and new habitats were opened. Thus, a biodiversity of as many as ten million animal and plant species was created on Earth. This diversity can in some ways be explained only in this way. So you can say: Evolution is life – and life is evolution!
Progress is not always a snail’s pace
The evolution continues to this day. In many cases, it happens so slowly that we don’t notice its impact throughout our lives. However, some changes occur within a few years. In particular, organisms with a short generation time can adapt relatively quickly to new environmental conditions.
An example of this is the house mouse). The species split into western and eastern subspecies after the last ice age. Since then, the two lines have evolved so far that they are genetically distinct. However, the differences are not yet so great that the members of these two lineages cannot mix with each other. Researchers at the Max Planck Institute for Evolutionary Biology in Plön are using this to investigate key evolutionary processes based on differences.
Bacteria have even shorter generation times than mice. Some of the microbes form several generations per day. Evolutionary changes can therefore be observed after only a few months. Bacteria are therefore an ideal model system for monitoring evolution live in the laboratory. And not only that – it can even be controlled. By changing the living conditions in culture vessels, researchers can direct the development of bacteria in different directions. Scientists from the Max Planck Institute for Evolutionary Biology discovered how bacteria Pseudomonas tolaasii they can combine to form clusters of cells. Thus, they found a possible path from unicellular to multicellular.
Evolution relies on the tried and tested
The results of Max Planck scientists and other research groups also show that evolution is often very conservative. It uses existing genes and gives them new tasks. This also explains why creatures as diverse as earthworms or fruit flies have so many genes that we humans also carry. Gene reassignment is a central principle of evolution and the environment plays a key role in this.