The paper that explained why every living thing on Earth exists was rejected by 15 journals before anyone took it seriously - and the idea it contained is stranger than most science fiction

Key Points:

• In 1967, Lynn Margulis published a revolutionary paper proposing the endosymbiotic theory, which suggests that complex cells evolved through ancient mergers between separate organisms, specifically bacteria that became mitochondria and chloroplasts.
• The theory posits that mitochondria and chloroplasts were once free-living bacteria engulfed by larger cells, forming a symbiotic relationship that was essential for the development of complex life, with mitochondria producing energy and chloroplasts enabling photosynthesis.
• Initially rejected by fifteen scientific journals due to skepticism and the unconventional nature of the hypothesis, Margulis's work eventually gained acceptance after she provided multiple lines of evidence, including mitochondrial DNA characteristics, reproduction methods, membrane structure, and antibiotic sensitivity.
• Endosymbiotic theory challenges traditional views of evolution as gradual change by highlighting cooperation and mergers as fundamental mechanisms, reshaping our understanding of life as a community of intertwined lineages rather than isolated organisms.
• The theory has influenced broader evolutionary biology, revealing additional examples of secondary and tertiary endosymbiosis and highlighting the prevalence of horizontal gene transfer, thus portraying the history of life as a complex web of genetic exchange rather than a simple branching tree.