How Did Life Actually Originate on Earth?: Theories of Evolution

There are the most different evolution theories, but the most well-known are probably those of Darwin and Lamarck. But also the Miller experiment and the black smokers show other possibilities of the origin of living beings on earth. Evolution is the phylogenetic development of animal and plant species. The living beings want to adapt to their environment by this development. The evolution takes place in the course of many generations. We will now go into more detail about the most interesting and well-known theories:

Darwinism

Darwinism is the name given to the theory of evolution by Charles Darwin (1809 – 1882). This involves evolution by natural selection. Darwin claimed that evolution is accelerated specifically by the competitive behavior that occurs in nature, because in the struggle for food and habitat, only the best adapted and strongest creatures survive. In addition, it is more likely that these, best adapted creatures, will also reproduce. Thus, their strengths are passed on to their offspring. The weaker members of the species are less likely to reproduce due to competition, among other things – they eventually die out. Thus, according to Darwin, species do not evolve according to a predetermined plan, but rather random mutations (changes in genetic material) create new variants of a species that replace their weaker predecessors through their strength and adaptation to the environment. If the offspring with the new characteristics eventually diverge so far from their ancestors or other offspring with new characteristics that they can no longer reproduce with them, then a new species has emerged. Darwin himself later applied his theory to humans.

Lamarck’s theory of evolution

Lamarck (1744 – 1829), a French botanist and zoologist, was one of the most important biologists in the early 19th century. His thinking was that every living thing wants to live in harmony with their environment. However, since this is in a constant state of change, species must also change in order not to become extinct. His theory of evolution was based on two “observations”. The first was that living things eventually lose the features they don’t need and instead develop features they do need in their environment through constant use of the organs in question. Lamarck’s second observation was that living things inherited these acquired traits to their offspring. The most famous example of his theory is the long neck of giraffes. Due to a drought, food could only be found on tall trees. The giraffes had to stretch their necks, which made them longer over time. This longer neck was passed on to their offspring. Lamarck’s theory of evolution was the scientific explanation of species diversity. However, Lamarck’s theory of evolution has a major flaw in that it assumes that abilities acquired during life can be inherited. For this to happen, the genetic information in the sex cells would have to change accordingly. According to our current knowledge, however, this is not possible.

Miller-Urey experiment

Stanley Miller and Harald Urey attempted to recreate Earth’s primordial atmosphere in a test tube in 1952. The primordial atmosphere was supposedly composed of the high-energy gases hydrogen, methane, and ammonia, which could react using available energies to form organic compounds. In the experiment, the presumed components of the primordial atmosphere were exposed to electrical spark discharges. These were intended to simulate lightning strikes. The gases that condensed in the cold were then collected in a flask filled with water, which was supposed to represent the primeval ocean. By heating the flask, these gases were finally transported back into the primordial atmosphere and again exposed to the lightning strikes. The experiment continued like this for a week. After one day, the water had already turned pink; by 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 of life. The criticism of the experiment of Miller and Urey is, however, that it is not proven whether the assumed substances were really present in the primordial atmosphere.

The black smokers

Black smokers are hydrothermal vents located at about 2000 meters at the bottom of the deep sea. They are cone-shaped chimneys formed by the deposition of minerals. From them emerges 400-degree hot and mineral-rich water, which cools by meeting the 2-degree cold water of the deep sea, forming the minerals, which in turn are deposited on the chimneys. In this way, the chimneys reach heights of 20 to 25 meters. The black smokers grow up only where the volcanic activity comes to the surface. Through the fissures in the oceanic crust, cold seawater thus penetrates kilometers deep into the earth’s interior, heats up and reacts with the ocean floor rocks. Then, laden with volcanic gases, metals and sulfur, it returns to the ocean floor and flows out. Because of the high pressure, the water does not begin to boil despite the high temperature. But although these conditions prevail there, archaic bacteria can only thrive there, because they can only begin to grow at 90 degrees and can also tolerate temperatures far above 100 degrees. Therefore, it is assumed that the first life forms must have evolved without oxygen in the deep sea. In doing so, they used hydrogen sulfide as an energy source in the lightless environment to convert carbon dioxide into organic compounds.

Conclusion

Even today, there is still no clarity about the origin of living things on Earth. However, we can rule out a few theories with our current knowledge, such as Lamarck’s.