10 ways the EES can work without Natural Selection


The Extended Evolutionary Synthesis (EES) is a modern synthesis of evolutionary theory that incorporates a wider range of factors than the traditional theory of natural selection. While natural selection is still considered to be a driver of evolution, the EES also recognizes the importance of other factors.

Here are 10 ways that the EES explains evolution without natural selection:

  1. Random genetic drift: random genetic drift can lead to the fixation of new alleles, even if they are not beneficial or harmful. This can happen when a population is small, or when there is a bottleneck event, such as a natural disaster.

Genetic drift is a random change in allele frequencies over time, while natural selection is the process by which heritable traits that improve an organism's fitness are passed on to the next generation. Genetic drift does not take into account an allele's beneficial or harmful effects (natural selection), it simply changes allele frequencies by chance.

  1. Gene flow: Gene flow can introduce new alleles into a population, which can lead to evolutionary change. This is especially true if the new alleles are beneficial. Gene flow can occur without any natural selection taking place. For example, if two populations of the same species are separated by a mountain range, gene flow can occur through birds that fly over the mountain range. The birds will carry genes from one population to the other, even though there is no natural selection occurring between the two populations.

  2. Niche construction: Niche construction can lead to the evolution of new traits, even if those traits are not directly beneficial to the organism as required with natural selection. For example, beavers build dams, which create new habitats that favor the evolution of beaver-like traits.

  3. Developmental plasticity: Developmental plasticity is the ability of an organism to develop different traits depending on its environment. This can lead to the evolution of new traits, even if the environment is not changing. For example, some fish can change their sex depending on the sex ratio of the population without change in their DNA sequence therefore no natural selection.

Epigenetic plasticity is included in  Developmental plasticity. The organism's genes can be turned on or off in a way that is influenced by the environment. This is called epigenetics. For example, exposure to stress can cause certain genes to be turned off, which can lead to changes in the organism's phenotype.

This occurs without DNA sequence changes ergo no natural selection.

  1. Epistasis: Epistasis is the interaction of genes. This means that the effect of one gene on a trait can be influenced by other genes. Epistasis can lead to the evolution of new traits, even if the individual genes involved are not beneficial on their own.

  2. Mutational bias: Mutational bias is the tendency for certain types of mutations to occur more frequently than others. This can lead to the evolution of new traits, even if the mutations themselves are not beneficial. It's now know epigenetics controls biased mutations apart from random natural selection mutations.

  3. Self-organization: Self-organization is the process by which complex structures emerge from simple interactions. This can lead to the evolution of new traits, even if there is no external selection pressure. 

  4. Evolvability: Evolvability is the ability of a population to change in response to selection. The EES argues that evolvability is an important factor in evolution, and that it can be influenced by non-selective forces.

  5. History: The EES argues that the past history of a population can influence its future evolution. This is because the past history of a population can affect its genetic diversity, its niche construction abilities, and its evolvability.

  6. Contingency: The EES argues that evolution is not deterministic. This means that the future evolution of a population is not entirely predictable from its past history. This is because evolution is influenced by random events, such as genetic drift and gene flow.

The EES is a complex and evolving field of study. The 10 examples listed above are just a few of the ways that the EES explains evolution without natural selection. As our understanding of evolution continues to grow, it is likely that we will discover even more ways that non-selective forces can drive evolutionary change.


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