Lynn Margulis and the endosymbiont hypothesis: 50 years later
Biologist Lynn Margulis first made the case for endosymbiosis in the 1960s, but for many years other biologists were skeptical. Although Jeon watched his amoebae become infected with the x-bacteria and then evolve to depend upon them, no one was around over a billion years ago to observe the events of endosymbiosis. Why should we think that a mitochondrion used to be a free-living organism in its own right? It turns out that many lines of evidence support this idea. Most important are the many striking similarities between prokaryotes (like bacteria) and mitochondria:
Lynn Margulis and the endosymbiont hypothesis: ..
Ivan Wallin proposed in 1927 that bacteria might represent the fundamental cause of the origin of species, and that the creation of a species may occur via endosymbiosis.
In the late 20th century, Lynn Margulis claimed that microorganisms are one of the major evolutionary forces in the origin of species, endosymbiosis of bacteria being responsible for the creation of complex forms of life.
Margulis' theory of symbiogenesis
Margulis emphasizes that bacteria and other microorganisms actively participated in shaping the Earth, and helped create conditions suitable for life (e.g., almost all eukaryotes require oxygen, and only developed after cyanobacteria have produced enough atmospheric oxygen).
Lynn Margulis was so intrigued by the idea of symbiosis, she became a contributor to the Gaia hypothesis first proposed by James Lovelock. In short, the Gaia hypothesis asserts that everything on Earth—including life on land, the oceans, and the atmosphere—work together in a sort of symbiosis as if it were one living organism.