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Lynn Margulis

One thing I remember from my childhood is being really thrilled by scientific theories that seemed counterintuitive at first, but deeply elegant once you heard the details & supporting arguments. I was really excited to learn about plate tectonics and evolution, for example. More specifically, the theory that organelles in complex cells originated with symbiotic relationships between distinct, seperate organisms, was particularly fascinating to me. A few scientists flirted with this idea over the years, but the first person to really push it seriously and accumulate supporting evidence, was Lynn Margulis, was sadly died this week.

Aside from the inherent beauty and elegance of this theory, it has an enormously important practical application in the study of human origins. Since the organelles in modern cells that still have their own DNA, as prokaryote-descendants, reproduce non-sexually, their mutation rate is speady and predictable. Thus, unlike the host cell DNA of a complex organism like a human, a comparison of mitochondria DNA between two individuals can accurately indicate the amount of time that has elapsed since diversion. This has been used to discover the order and pattern of humanity's spread to the Americas and the South Pacific. (Often overthrowing previous theories.)