Question

Describe the "Modern Synthesis" of the theory of evolution. Include all aspects of Darwin's original theory and how it has been improved/added to with new discoveries since his time.

Answer 1

The Modern Synthesis or Synthetic theory of evolution was proposed by Darwin to explain the evolution of the species trough the Natural Selection. Darwin’s theory is based on three premises and two conclusions:

Firs premise: The populations have a great reproductive potential capacity to grow up indefinitely.

Second premise: the available resources to the populations (food, breeding places) are limited and their increase is lesser than the necessary one to the indefinite grow of the population. A competition between members of the population arise. The “fight for existence” and the increase of the individual's ability to compete, survive, and reproduce. A selection of the most competent individuals and in consequence a selection of the more competent features related to their fitness.

Third premise: A genetic variability exists between individuals of a population.

Based on these premises, Darwin conclude:

1. Select individuals for its greater fitness, will leave more offspring than other individuals.
2. So, the genes of these selected individuals will be represented in the next generations. A continuous selection throughout generations will change gradually the composition of the populations whose members will have different morphologic features with respect to the ancestral population. These features could be so different to those from the ancestral population that it could be considered a new species. This process was named Natural Selection by Darwin.

In sum, according to Darwin's natural selection, the species and the changes in them are the result of a cluster of coincidences. The changes are produced only by mutations in the genes and by the combination of those of the parents, and then if, by chance, the inherited traits are an advantage in a particular environment, the individuals that have them will have more possibilities of survive and reproduce. In short, the best adapted are "naturally selected".

However, since Darwin’s time, the Modern Synthesis with its Natural Selection was not enough to explain the evolution.

The integration of the genetic into the Natural Selection Theory was the key to establish the basis of the Modern Theory of Evolution:

1. Evolution can be explained through gradual genetic changes in populations, which are produced by Natural Selection acting on small mutations or recombinations.
2. The major evolutionary changes (ie, macroevolution and speciation) can be explained by known mechanisms of genetic change.