How did life on earth actually come about? - Theories of evolution

There are a variety of theories of evolution, but the best known are probably those of Darwin and Lamarck. But also the Miller experiment and the black smoker show further possibilities of the emergence of organisms on the earth. Evolution is the phylogenetic evolution of animal and plant species. Living beings want to adapt to their environment through this development. Evolution takes place over many generations. Now let's take a closer look at the most interesting and well-known theories:

Darwinism

Darwinism is the evolutionary theory of Charles Darwin (1809 - 1882). It is evolution through natural selection. Darwin claimed that evolution is accelerated by nature's competitive behavior, as only the best-adjusted and strongest living beings survive in the battle for food and living space. In addition, these best-adapted creatures are more likely to multiply. As a result, their strengths are passed on to their offspring. Among the weaker conspecifics, it is less likely due to the competition that they multiply - they eventually die out.

According to Darwin, species do not develop according to a given plan, but random mutations (changes in the genetic material) create new variants of a species that, through their strength and adaptation to the environment, replace their weaker predecessors. If the offspring with the new traits eventually deviate so far from their ancestors or other offspring with new traits that they can no longer reproduce with them, then a new species has emerged. Darwin himself later transferred his theory to humans.

Lamarck's theory of evolution

Lamarck (1744 - 1829), a French botanist and zoologist, was one of the most important biologists of the early 19th century. His considerations were that every living entity wants to live in harmony with their environment. However, as these are in constant change, so must the species, so as not to die out. His theory of evolution was based on two "observations".

The first was that living beings eventually lose their traits they do not need by developing the traits they need in their environment through constant use of the organs concerned. Lamarck's second observation was that the living beings inherited these acquired traits to their offspring.

The best known example of his theory is the long neck of giraffes. Due to a drought period, food was only found on tall trees. The giraffes had to stretch their neck, which made it longer in time. This longer neck was passed on to the offspring.

Lamarck's theory of evolution was the scientific explanation of biodiversity. The Lamarckian theory of evolution, however, has a big mistake, since it assumes that the skills acquired in the course of life can be inherited. For this, the genetic information in the gender cells would have to change accordingly. However, according to our current knowledge, this is not possible.

Miller-Urey experiment

Stanley Miller and Harald Urey tried in 1952 to re-create the original atmosphere of the earth in a test tube. The primeval atmosphere allegedly consisted of the high-energy gases hydrogen, methane and ammonia, which could react by means of existing energies to organic compounds. In the experiment, the suspected components of the urine atmosphere were subjected to electrical spark discharges. These should simulate lightning strikes. The gases that condensed in the cold were then collected in a water-filled flask intended to represent the urocean. By heating the flask, these gases were finally returned to the original atmosphere and re-exposed to lightning strikes.

The experiment continued for a week. After one day, the water had already turned pink, at the end of the week the water in the flask was deep red to brownish in color and cloudy. A complex mixture of organic compounds had formed in the water, including simple fatty acids, amino acids and sugars. The best conditions for the emergence life. The criticism of the experiment by Miller and Urey is however, that it is not proven whether the suspected substances were really present in the Uratmosphäre.

The black smoker

Black smokers are hydrothermal wells located at about 2000 meters at the bottom of the deep sea. These are cone-shaped chimneys, which were created by the deposition of minerals. From them comes 400 degrees hot and mineral water, which cools by the encounter with the 2 degrees cold water of the deep sea and thus forms the minerals, which in turn deposited on the chimneys. The vents reach heights of 20 to 25 meters in this way.

The black smokers only grow up where the volcanic activity comes to the surface. Through the fissures in the oceanic crust, cold seawater penetrates kilometer-deep into the interior of the earth, heats up and reacts with the ocean floor rocks. Then it returns loaded with volcanic gases, metals and sulfur back to the seabed and flows out there. Because of the high pressure, the water does not start to boil despite the high temperature.

However, even though these conditions prevail, archaic bacteria can only thrive there, because they can only start to grow at 90 degrees and tolerate temperatures well over 100 degrees. Therefore, it is assumed that the first life forms without oxygen in the deep sea must have arisen. They used hydrogen sulfide as an energy source in the lightless environment to convert carbon dioxide into organic compounds.

Conclusion

Even today there is no clarity about the origin of living things on earth. However, we can exclude a few theories with our current knowledge, such as Lamarck's.

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