Symbiogenesis - Evolution without Darwin


Natural selection is the process by which organisms that are better adapted to their environment are more likely to survive and reproduce, passing on their genes to the next generation. However, symbiogenesis is the process by which two organisms come together to form a mutually beneficial relationship. The initial steps of symbiogenesis would not be beneficial to either organism, so natural selection would not favor it.

For example, consider the case of mitochondria, which are the energy-producing organelles found in eukaryotic cells. Mitochondria are thought to have originally been free-living bacteria that were engulfed by another cell. The engulfed bacteria provided the host cell with energy, while the host cell provided the bacteria with a protected environment. Over time, the two organisms became so interdependent that they could no longer survive apart.

The initial steps of this process would have been very risky for both organisms. The engulfed bacteria could have been killed by the host cell's defenses, or the host cell could have been harmed by the bacteria's toxins. Natural selection would not have favored either organism taking such a risk.

There are a several explanations for how symbiogenesis could have gotten started without NeoDarwinism:

  1. Mutualistic symbiosis. This is the most common type of symbiosis, in which both partners benefit from the relationship. For example, the mitochondria and chloroplasts of eukaryotic cells are thought to have originated from bacteria that entered into a mutualistic relationship with an early eukaryotic cell without natural selection.

  2. Commensal symbiosis. In this type of symbiosis, one partner benefits while the other is unaffected. For example, many animals live in close association with algae or bacteria, which provide them with food or other benefits.

  3. Parasitic symbiosis. In this type of symbiosis, one partner benefits while the other is harmed. For example, many parasites live in or on other organisms, feeding off of their tissues or fluids.

  4. Facultative symbiosis. This type of symbiosis is not essential for the survival of either partner. For example, some plants can live in either a symbiotic or non-symbiotic relationship with fungi.

  5. Obligate symbiosis. This type of symbiosis is essential for the survival of both partners. For example, the termite gut microbiota is essential for the termite's ability to digest food.

  6. Sequential symbiosis. This type of symbiosis occurs when two or more symbiotic relationships are linked together. For example, the relationship between the mitochondria and chloroplasts of eukaryotic cells is thought to have evolved through a series of sequential symbiotic events.

It is important to note that these are just a few examples of the many ways that symbiogenesis can occur. The specific mechanisms involved in each case are still being investigated by scientists.

Whatever the explanation, it is clear that natural selection cannot explain the initial steps of symbiogenesis. This is one of the challenges that evolutionary biologists face in trying to understand the origins of life.

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