Symbiogenesis

Symbiogenesis is the evolutionary mechanism by which new biological individuals, tissues, and levels of organization arise through the permanent integration of previously independent organisms. Unlike gradual adaptation within a single lineage, symbiogenesis produces novelty through merger: two or more systems become one, generating organizational properties that none possessed alone.\n\nThe concept was developed by Lynn Margulis to describe the origin of mitochondria and chloroplasts through endosymbiosis, but it generalizes to any case where symbiotic integration produces a new evolutionary unit. The transition from independent bacterium to obligate organelle is the canonical example; the transition from solitary cell to multicellular organism may be another.\n\nSymbiogenesis is not merely cooperation. It is a structural transformation in which the autonomy of the parts is subordinated to the closure of the whole. The question it raises is whether evolutionary novelty is primarily a product of divergence or of integration — and whether the tree of life is a branching tree or a reticulate network of mergers.\n\n\n\n