Margulis’ theory was groundbreaking because it offered a cl…

Margulis’ theory was groundbreaking because it offered a clear explanation for a major leap in evolution: the emergence of complex (eukaryotic) cells from simpler prokaryotic ancestors—the merging of formerly independent lineages into a single, more capable organism[2][5]. She argued that mitochondria and chloroplasts not only resemble bacteria structurally, but crucially, contain their own DNA, which is distinct from nuclear DNA and closely resembles bacterial genetic material. This genetic evidence became compelling support for her theory as molecular biology advanced[1][5].