Lynn Margulis

Lynn Margulis was an American evolutionary biologist whose Serial Endosymbiotic Theory of eukaryotic cell development revolutionized the modern concept of how life arose on Earth. It was during the late 1960’s that she published her formative and also her most influential paper, “On the Origin of Mitosing Cells”. In her article, Margulis hypothesized that mitochondria and plastids owing to their similarities to earlier prokaryotic bacteria, might have originated endosymbiotically from prokaryotic progenitors, i.e these progenitors would have started living in close proximity in a mutualistic fashion, and this close knit association ultimately led to the formation of modern eukaryotic cells. Margulis’ article was notable as it was perhaps the first unified theory of eukaryogenesis. However this theory was met with a lot of hostility - being rejected about 15 times, before it was substantiated through genetic evidence.

Once the genes inside organelles were explored, it was seen that the genes inside chloroplasts of some species of algae bore little resemblance to the genes in the algae's nuclei, however chloroplast DNA, as it turns out was actually cyanobacterial DNA. Peptidoglycan layer (integral component of bacterial cell wall) was also noticed in the chloroplasts of glaucophytes. The DNA in mitochondria, meanwhile, resembled the group of bacteria that cause typhus. It became clear that symbiotic events had a profound impact on the organization and complexity of many forms of life and evolution is more flexible than was once believed.