This made perfect sense to Lyn Margulis, an evolutionary biologist who was once married to astronomer Carl Sagan. She put up with decades of skepticism and derision from older scientists before Woese and Doolittle identified the genetic data in chloroplasts that confirmed the theory.
The History of Evolutionary Thought → 1900 to present → Endosymbiosis: Lynn Margulis
https://evolution.berkeley.edu/the-history-of-evolutionary-t...
Lynn Margulis and the endosymbiont hypothesis: 50 years later