Evolutionary theories present as their main point the defense that the planet’s organisms undergo changes over time, and therefore are not immutable.
→ What is evolutionary theory based on?
Evolutionary theories claim that changes have occurred in organisms over the thousands of years on the planet. These changes can be seen, for example, in fossils of organisms that are not found on Earth today, but that have great similarities with present-day organisms. All existing evolutionary theories speak of change, differing only on how these changes took place.
→ Main evolutionary theories
Among the existing evolutionary theories, some deserve to be highlighted: Lamarkism , Darwinism and Neo- Darwinism .
One of the first theories that explained the evolution of living beings was the one proposed by Jean-Baptiste Lamack (1744-1829). To explain evolution, he suggested two laws: the law of use and disuse and the law of acquired characters.
The law of use and disuse explains that when an organism uses a certain part of the body a lot, that part develops more than others and those that are not used atrophy. The law of inheritance of acquired characters, in turn, states that characteristics acquired during life can be transmitted to descendants.
Lamarck’s theory has some flaws that deserve to be highlighted. The first one concerns the use and disuse, which cannot be considered a truth, since the characteristics of our organism are predetermined by genes, and the use and disuse could cause alterations in the predetermined limits. Another point worth mentioning concerns acquired characteristics that cannot be transmitted, as they are not present in our genetic information.
Darwinism brings together the evolutionary ideas proposed by Charles Darwin (1809-1882). According to this researcher, species change over time due to natural selection. For him, organisms live in a constant struggle for survival and only the fittest are able to survive, reproduce and pass on advantageous characteristics to their descendants.
Despite natural selection being a correct mechanism, Darwin was unable to explain how advantageous traits arose in organisms, nor how they were transmitted. This explanation was not possible because there was no knowledge about Genetics in that period.
- Neo-Darwinism or synthetic theory of evolution
Neo-Darwinism is a theory created with the contribution of several researchers to explain factors that Darwin did not understand when he presented his famous theory. In other words, we say that neo-Darwinism consists of the theory of natural selection plus genetic knowledge acquired later. As such, neo-Darwinism embodies the idea of genetic mutation and recombination.