Endosymbiotic hypothesis

The endosymbiotic theory, known to academics as the serial endosymbiosis theory (SET), is a scientific theory concerning the origins of mitochondria, plastids (e.g. chloroplasts), and nuclei in eukaryotic cells. According to this hypothesis, these organelles arose from free-living bacteria that were taken inside another cell as endosymbionts.

Creation science critique of the edosymbiotic hypothesis

Dr. Carl Wieland is the Managing Director of Creation Ministries International

Citing a biology textbook Creation Ministries International writes:

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Sometimes it is stated more cautiously: ‘In the endosymbiont theory, the ancestor of the eukaryotic cell (we will call this organism a protoeukaryote) is presumed to have been a large, anaerobic, heterotrophic prokaryote that obtained its energy by a glycolytic pathway. Unlike present-day bacteria, this organism had the ability to take up particulate matter … . The endosymbiont theory postulates that a condition arose in which a large, particularly complex, anaerobic prokaryote took up a small aerobic prokaryote into its cytoplasm and retained it in a permanent state [emphasis added].’ Whichever way it is stated, it is given an aura of authority and certainty by its frequent repetition in writings on cell biology. Many students find it convincing. However, like many evolutionary ideas, it may look solid from a distance, but gaps appear on close scrutiny. The evidence for the endosymbiont theory revolves around selected similarities between mitochondria and bacteria, especially the DNA ring structure. However, these similarities do not prove evolutionary relationship. There is no clear pathway from any one kind of bacteria to mitochondria, although several types of bacteria share isolated points of similarity. Indeed, the scattered nature of these similarities has left plenty of room for a less-publicized ‘direct evolution’ theory of mitochondrial origin, in which they never had any free-living stage. There is enough diversity among the mitochondria of protozoa to make evolutionists wonder if endosymbiotic origin of mitochondria occurred more than once. Mitochondrial DNA The endosymbiont theory implies that there should be considerable autonomy for mitochondria. This is not the case. Mitochondria are far from self-sufficient even in their DNA, which is their most autonomous feature. Mitochondria actually have most of their proteins coded by nuclear genes, including their DNA synthesis enzymes.

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Problems

See also: Theory of Evolution and Cases of Fraud, Hoaxes and Speculation and Creation science and Intelligent design

Ernst Haeckel's homology arguments were later shown to be erroneous evolutionary speculation and a fraud. Please see: Theory of Evolution and Cases of Fraud, Hoaxes and Speculation

• Neither mitochondria nor plastids can survive in oxygen or outside the cell, having lost many essential genes required for survival.
• A large cell, especially one equipped for phagocytosis, has vast energetic requirements, which cannot be achieved without the internalisation of energy production (due to the decrease in the surface area to volume ratio as size increases).

History

See also: Theory of Evolution and Cases of Fraud, Hoaxes and Speculation and Intelligent design and Creation science

The endosymbiotic hypothesis was first articulated by famed Russian botanist Konstantin Mereschkowski in 1905. Mereschkowski based his theory in part on work done by botanist Andreas Schimper, who had observed in 1883 that the division of chloroplasts in green plants closely resembled that of cyanobacteria. Schimper had himself tentatively proposed (in a footnote) that green plants could have arisen from the symbiosis of two simpler organisms. In the 1920s, Irvin Wallin, a professor at the University of Colorado Medical School, extended the idea of an endosymbiotic origin to the mitochondria. These theories were initially dismissed (or ignored) by the scientific community. More detailed electron microscopic comparisons between cyanobacteria and chloroplasts (for example, studies by Hans Ris) combined with the discovery that plastids and mitochondria contain their own DNA (which had recently been identified as the hereditary material of organisms) led to a resurrection of the idea in the 1960s.

The endosymbiotic hypothesis was advanced in 1967 by American biologist Lynn Margulis. A young faculty member at Boston University, Margulis authored a theoretical paper entitled The Origin of Mitosing Eukaryotic Cells. The paper, however, was "rejected by about fifteen scientific journals," Margulis recalled. It was finally accepted by The Journal of Theoretical Biology.

The possibility that peroxisomes may have an endosymbiotic origin has also been considered, although they lack DNA. Christian de Duve proposed that they may have been the first endosymbionts, allowing cells to withstand growing amounts of free molecular oxygen in the Earth's atmosphere. It is believed by evolutionists that over millennia these endosymbionts transferred some of their own DNA to the host cell's nucleus during the evolutionary transition from a symbiotic community to an instituted eukaryotic cell (called "serial endosymbiosis"). This hypothesis is thought to be possible because it is known today from scientific observation that transfer of DNA occurs between bacteria species, even if they are not closely related. Bacteria can take up DNA from their surroundings and have a limited ability to incorporate it into their own genome.

See Also

• Theory of Evolution
• Theory of Evolution and Cases of Fraud, Hoaxes and Speculation
• Evolution, Liberalism, Atheism, and Irrationality
• Evolutionism
• Symbiosis
• Cell