The main difference between Darwinism and Neo Darwinism is that Darwinism describes that favorable phenotypic variations that are inheritable are the driving force of speciation whereas Neo Darwinism describes that only genetic variations that are inheritable are the driving force of speciation. 

Darwinism and Neo Darwinism are two concepts describing the origin of new species, which leads to evolution. Darwinism is the original concept postulated by Darwin and Wallace while Neo Darwinism is a modification of the original theory.

Key Areas Covered

1. What is Darwinism
     – Definition, Theory, Significance
2. What is Neo Darwinism
     – Definition, Theory, Significance
3. What are the Similarities Between Darwinism and Neo Darwinism
     – Outline of Common Features
4. What is the Difference Between Darwinism and Neo Darwinism
     – Comparison of Key Differences

Key Terms

Darwinism, Genetic Variations, Natural Selection, Neo Darwinism, Phenotypic Variations, Speciation

What is Darwinism

Darwinism is the theory of biological evolution postulated by the English naturalist Charles Darwin (1809–1882) and others. It states that all species develop through the natural selection of favorable phenotypic variations that are inheritable. Thus, this increases the individual’s ability to compete, survive, and reproduce.

Figure 1: Human Evolution

Furthermore, the four basic tenets of Darwinism are as follows:

• Organisms produce more individuals, exceeding the level of individuals that can survive.
• These individuals have phenotypic variations among them that are inheritable.
• Among these different phenotypes, some are more suitable to the environment than the others.
• The fittest phenotypes accumulate within individuals over time as the natural selection of them, leading to the origination of new species.

What is Neo Darwinism

Neo Darwinism is a modified interpretation of Darwinian evolution in association with the Mendelian genetics and modern synthesis of natural selection. Therefore, it describes the major driving force of speciation as the accumulation of genotypic variations within a gene pool. Some also refer to Neo Darwinism as Modern synthetic theory of natural selection. Some supporters of Neo Darwinism were Romans, Huxley, Fisher, Fold, and Haldane.

Figure 2: Neo Darwinism

Moreover, mutations are responsible for the genotypic variations within a gene pool. Some mutations alter only a few nucleotides in the genome while others such as recombination cause bigger changes. However, both of them can be lucky accidents, which lead to new genotypes more suitable for the environment. Furthermore, reproductive isolation plays a key role in speciation in Neo Darwinism. It allows the differential amplification of the fittest genes within the gene pool. Therefore, the natural selection of fittest genes is considered to be leading to the origination of new species.

Similarities Between Darwinism and Neo Darwinism

• Darwinism and Neo Darwinism are two concepts describing the driving forces of speciation.
• Both make attempts to describe the evolution of organisms.
• Furthermore, different types of variations are described as forcing to speciation.
• The changes in each concept are inheritable.
• Moreover, both concepts describe natural selection in different bases.

Difference Between Darwinism and Neo Darwinism

Definition

Darwinism refers to the theory of the evolution of species by natural selection advanced by Charles Darwin while Neo Darwinism refers to a modern version of Darwin’s theory of evolution by natural selection, incorporating the findings of genetics. Thus, this is the main difference between Darwinism and Neo Darwinism.

Significance

While Darwinism is the original theory, Neo Darwinism is a modification based on the Mendelian genetics and modern synthesis of natural selection.

Driving Force of Speciation

The major driving force described by Darwinism is the accumulation of phenotypic variations while the major driving force described by Neo Darwinism is the accumulation of genetic variations.

Reason for Variation

Another difference between Darwinism and Neo Darwinism is the cause behind variation. Darwinism does not describe the reason for variation while Neo Darwinism describes the reason for variation as mutation, genetic recombination, natural selection, and reproductive isolation.

Variations Occur in

In Darwinism, variations occur in individuals while in Neo Darwinism, variations occur in the gene pool. Hence, this is also an important difference between Darwinism and Neo Darwinism.

Type of Natural Selection

In Darwinism, natural selection is the survival of the fittest and the removal of the unfitted organisms during a course of time while Neo Darwinism, natural selection is the differential amplification of the fittest genes and genotypes.

Effect of Reproductive Isolation

Also, one other difference between Darwinism and Neo Darwinism is that Darwinism does not believe isolation as a major component of evolution while Neo Darwinism believes isolation as a major component of evolution.

Conclusion

Darwinism is the original concept developed by Darwin describing the origin of new speciation. Accumulation of the fittest phenotypic variations within individuals is the main driving force of speciation according to Darwin. Therefore, natural selection is the survival of the fittest in the environment. On the other hand, Neo Darwinism is a modified theory of Darwinism, describing the origin of species according to a genetic basis. Thus, genetic variations are the major driving force of Neo Darwinism. Here, natural selection is based on the differential selection of fittest genes within a gene pool. Accordingly, the main difference between Darwinism and Neo Darwinism is the type of variations and type of natural selection.

References:

1. “Darwin’s Theory Of Evolution.” Darwin’s Theory Of Evolution, Available Here.
2. Noble, Denis. “Neo-Darwinism, the modern synthesis and selfish genes: are they of use in physiology?.” The Journal of physiology vol. 589,Pt 5 (2010): 1007-15. doi:10.1113/jphysiol.2010.201384.

Image Courtesy:

1. “Darwin-chart” (Public Domain) via Commons Wikimedia   
2. “Modern Synthesis” By Ian Alexander – Own work (CC BY-SA 4.0) via Commons Wikimedia  

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