Symbiogenesis
Discussion
Herbert Spencer:
H.J. Spencer:
"In the course of her research, Margulis discovered that an American anatomist, I. E. Wallin proposed in the 1920s that several vital cell components, like mitochondria and chloroplasts, originated as symbiotic bacteria. When he was not being ignored, he was strongly condemned for daring to suggest that 'germs' could contribute anything positive to life forms that were rigidly believed to exist as only animals or plants. Additionally, in reading old biology books, Margulis did find links to the symbiogenesis ideas of Merezhovsky. This stimulated her focus on the role of bacteria and her laboratory evidence that symbiotic associations between prokaryotic bacteria were absorbed into eukaryotic cells in the form of forerunners of distinct, independent organelles in a process that Margulis called Endosymbiosis (some symbionts living within a larger organism). Since Margulis proposed that this process had occurred several times over extended timeframes, she added the word 'serial' to emphasize its recurrence; so this is why she has described her theory as Serial Endosymbiosis Theory(or SET)."