Although every scientific community has no doubt about biological evolution, it is a very complex fact that has many questions. Currently there are several theories that try to explain it.
Neo-Darwinism or Synthetic Theory of Evolution
The most accepted theory currently is the Synthetic Theory of Evolution or Neo-Darwinism, based on Darwinism but, applying current knowledge of genetics, which makes it possible to explain the variability of individuals of a species and how these characters are inherited from an individual to their parents.
Now we know that living things are different because so is the DNA in their cells. The reproductive cells (gametes) transmit the characters of both parents to the offspring, all of which are different from each other.
In addition to sexual reproduction, another cause of genetic variability is mutations. They are alterations that occur at random in the DNA of the cells that are transmitted to the offspring when they occur in the DNA of the reproductive cells. These mutations can be beneficial, neutral, or harmful. If the mutation is favorable, this characteristic allows the individual to have an easier time surviving and having offspring, and for this characteristic to be transmitted to their descendants. On the other hand, if the mutation means that it is less adapted to living in the conditions of the environment, it will eventually disappear, since the individuals who carry it will have greater problems to survive and more difficulties to have offspring to whom they can transmit this alteration.
The synthetic theory or neo-Darwinism is based on these principles:
- Acquired characters are not inherited. Like Darwin, they deny what Lamarck claimed.
- The genetic variations that exist between individuals are due to mutations and the random combination of genes in sexual reproduction.
- The natural selection acts on individuals in a population, making the population evolves adapting to environmental conditions.
- The evolution of a population is a gradual process, in which the small variations that occur in the DNA of the individuals of a population accumulate . When, at some point, the differences in genes are so great, a new species can be generated. Individuals of this new species will not be able to reproduce with individuals of the original species.
Although this theory is currently the most accepted, there are other theories that believe that it is not entirely correct.