How did life actually originate on earth? – Evolution theories

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

Darwinism

Darwinism is the evolutionary theory of Charles Darwin (1809 – 1882). This is evolution through natural selection. Darwin claimed that evolution is accelerated specifically by the competitive behavior that occurs in nature, since only the best adapted and strongest creatures survive in the struggle for food and habitat. Also, these best-adapted creatures are more likely to reproduce as well. As a result, their strengths are passed on to their offspring. It is less likely that the weaker conspecifics will reproduce, partly because of the competition – they eventually die out.

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

Lamarckian theory of evolution

Lamarck (1744 – 1829), a French botanist and zoologist, was one of the most important biologists of the early 19th century. His reasoning was that every living being wants to live in harmony with their environment. However, since this is in constant change, the 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 features they don’t need and develop features they need in their environment through constant use of those organs. Lamarck’s second observation was that living beings passed on these acquired characteristics to their offspring.

The most famous example of his theory is the giraffe’s long neck. Due to a period of 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 offspring.

Lamarck’s theory of evolution was the scientific explanation of species diversity. However, the Lamarckian theory of evolution has a major flaw in that it assumes that skills acquired throughout 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

In 1952, Stanley Miller and Harald Urey attempted to recreate the earth’s primordial atmosphere in a test tube. The primeval atmosphere allegedly consisted of the energy-rich gases hydrogen, methane and ammonia, which could react to form organic compounds using the available energies. In the experiment, the suspected components of the primordial atmosphere were exposed to electrical spark discharges. These should 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 primordial 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. However, the criticism of the experiment by Miller and Urey is that it has not been proven whether the suspected substances were really present in the primeval atmosphere.

The black smokers

Black smokers are hydrothermal vents located about 2000 meters at the bottom of the deep sea. These are cone-shaped chimneys formed by mineral deposits. Water with a temperature of 400 degrees and containing minerals emerges from them, which cools down when it meets the 2 degrees cold water of the deep sea and thus forms 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 only grow where volcanic activity comes to the surface. Cold seawater penetrates kilometers deep into the earth’s interior through the cracks in the oceanic crust, heats up and reacts with the ocean floor rocks. It then returns to the sea floor laden with volcanic gases, metals and  sulfur  and emanates from there. Because of the high pressure, the water does not boil despite the high temperature.

But although these conditions prevail there, archaic bacteria can only thrive there, because they can only start growing at 90 degrees and tolerate temperatures well above 100 degrees. It is therefore assumed that the first forms of life must have evolved without oxygen in the deep sea. In the lightless environment, they used hydrogen sulfide as an energy source to convert carbon dioxide into organic compounds.

Conclusion

Even today there is still no clarity about the origin of living beings on earth. However, we can rule out a few theories with what we know today, such as Lamarck’s.