Endosymbiotic Theory

Lynn Margulis's 1967 proposal that mitochondria and chloroplasts originated as free-living bacteria engulfed by ancestral cells was initially ridiculed but is now a cornerstone of evolutionary cell biology. This theory explains the double membranes and circular DNA in these organelles, with human mitochondrial DNA spanning 16,569 base pairs. It is faster than the average discovery in resolving long-standing puzzles about organelle evolution, and it outperforms Cell Theory in explaining the origin of eukaryotic complexity, adding a crucial evolutionary layer to the cellular framework.