Symbiogenesis challenges NeoDarwinism


In her article "Symbiogenesis and the New Synthesis," Lynn Margulis argues that the theory of symbiogenesis, which proposes that new species can arise through the fusion of genomes from different organisms, challenges the central tenets of neo-Darwinism.

Neo-Darwinism is the prevailing theory of evolution, which holds that all new species arise through the process of natural selection acting on random mutations. Margulis argued that symbiogenesis is a much more important mechanism of evolutionary change than neo-Darwinism allows for.

One of the main ways in which symbiogenesis challenges neo-Darwinism is by providing a mechanism for the rapid emergence of new and complex traits. Neo-Darwinism holds that new traits can only arise gradually, through the accumulation of small, random mutations. However, symbiogenesis can allow for the sudden emergence of new traits by combining the genomes of two or more organisms.


For example, the mitochondria and chloroplasts in eukaryotic cells are thought to have arisen through endosymbiosis, a type of symbiosis in which one organism lives inside another. Mitochondria are thought to have originated from bacteria, while chloroplasts are thought to have originated from cyanobacteria. The fusion of the genomes of these endosymbionts with the genomes of their host cells would have resulted in the sudden emergence of new and complex traits, such as the ability to produce energy from food (mitochondria) or to photosynthesize (chloroplasts).

Another way in which symbiogenesis challenges neo-Darwinism is by providing a mechanism for cooperative evolution. Neo-Darwinism is often seen as a competitive theory of evolution, in which organisms are constantly struggling to survive and reproduce. However, symbiogenesis shows that organisms can also cooperate with each other to their mutual benefit.

For example, many plants and animals have symbiotic relationships with bacteria. Some of these bacteria help their hosts to digest food, while others provide them with essential nutrients. The cooperation between these organisms has allowed them to evolve new and complex traits that would not be possible on their own.

Margulis's theory of symbiogenesis has been controversial since she first proposed it in the 1960s. However, it has gained increasing acceptance in recent years, as more and more evidence has emerged to support it. Today, symbiogenesis is widely recognized as a major driving force in evolution.

Here are some specific examples of how symbiogenesis challenges neo-Darwinism:

  • Neo-Darwinism has difficulty explaining the origin of eukaryotic cells. Eukaryotic cells are much more complex than prokaryotic cells, and they have a number of features that are not found in prokaryotes, such as a nucleus, mitochondria, and chloroplasts. Margulis's theory of endosymbiosis provides a plausible explanation for the origin of these features.

  • Neo-Darwinism has difficulty explaining the rapid emergence of new species during the Cambrian Explosion. The Cambrian Explosion was a period of rapid evolutionary change that occurred about 540 million years ago. During this time, many new and complex animal body plans appeared. Margulis has argued that symbiogenesis played a major role in the Cambrian Explosion.

  • Neo-Darwinism has difficulty explaining the evolution of complex social behaviors, such as those found in humans and other animals. Margulis has argued that symbiogenesis can help to explain the evolution of these behaviors by providing a mechanism for cooperation between individuals.

Overall, Margulis's theory of symbiogenesis provides a new and exciting way to think about evolution. It challenges the central tenets of neo-Darwinism and suggests that cooperation and symbiosis are just as important as competition in driving evolutionary change.

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