Modern Evolutionary Theories and Principles

Neodarwinism

This theory, born in 1947, defines evolution based on six core principles:

1. Refusal of Lamarckism

   It does not accept the theory of acquired characteristics.

2. Variability: Mutation and Recombination

   Individuals with asexual reproduction have mutation as the only source of variability. Individuals in sexual reproduction involve the process of genetic recombination.

3. Natural Selection Acts on Genetic Variability

   The individual is the bearer of different alleles, and natural selection acts on these varieties.

4. Evolution Occurs in the Population, Not Individuals

   A population is defined as a group of individuals of the same species that share an area and can crossbreed to produce fertile offspring. Populations survive, change, and evolve, while individuals die with the same genes they had at birth.

5. Evolution Takes Place Gradually

   Evolution is the result of small changes in a species that occur over many years.

6. Isolation Between Populations

   Isolation is essential for a population to become a different species. As Dobzhansky showed, populations have different alleles and retained genes. This fact led to the idea of balanced polymorphism, i.e., the superiority of heterozygotes.

Sociobiology

This theory, initially formulated by Edward O. Wilson, is based on the existence of hierarchies in most animal societies. The most successful individuals are those who lead, and this hierarchy is attributed to natural selection.

Sociobiologists also consider the behavior of individuals to be driven by a primary objective. Aggressiveness tends to eliminate rivals, and altruism is exercised towards individuals of the same family. This concept is known as the Selfish Gene Theory.

Neutralism

The creators of this theory believe that if the majority of genetic differences were subject to natural selection, variability would be short-lived: beneficial variants would expand and harmful variants would disappear.

Therefore, they assert that the majority of mutations neither benefit nor harm individuals; they remain neutral and either persist or disappear randomly.

Punctuated Equilibrium

This theory proposes three main points:

1. Species do not follow a single evolutionary line but several.
2. Transformation takes place in leaps, with species alternating periods of stasis with stages of speciation.
3. Transformation into new species takes place when a small population becomes isolated.