Lynn Margulis lived from 1938 – 2011.  Her most significant legacy is her contribution to the field of endosymbiotic theory.  She fought for years to defend the validity of her ideas, and they are now generally accepted as fact.

Endosymbiosis is a theory that states that all eukaryotes (organisms with cells that contain nuclei), including humans, are descended from a combination of bacteria and archaea.  There are three domains of life:  bacteria, archaea (single-celled organisms that are similar to bacteria but different in structure), and  eukaryotes.  Dr. Margulis’ theory states that all eukaryotes evolved from a combination of specific archaea and bacteria that combined into the same individual and began to reproduce as a single individual.

This theory was intensely controversial because in standard evolutionary theory, populations usually evolve into separate groups (with the exception of species hybridization, which is rare).  But in Dr. Margulis’ theory the organisms combined to make a new individual, which went on to establish a whole new domain of life.  Today, her theory is generally accepted, because she was able to show the extreme similarity between mitochondria and some kinds of bacteria.  This theory revolutionized the field of evolutionary biology.

Dr. Margulis was also involved in formulating the Gaia hypothesis, the idea that all life on earth (the biota) is in symbiosis with the atmosphere and other non-living parts of earth.  Although she collaborated extensively with James Lovelock, she rejected his metaphor of the Earth as being one living organism.

It is unfortunate that Dr. Margulis spoke out against the idea that the HIV virus causes AIDS.  In this, she joins a long line of scientists who were brilliant and right about a lot of things, and horribly wrong about some other things (see:  Dr. Fred Hoyle, brilliant astronomer, strange, strange man).  Dr. Margulis had a tendency to devote herself to an idea and defend it to the death, and it just so happened that in the case of endosymbiotic theory, she was right.

Geek Bonus:  Remember how George Lucas ruined Star Wars by saying that the Force involved using midichlorians?  Of course you do.  Well, the idea of midichlorians is that they are in us but also separate from us.  This was inspired by the very real existence of mitochondria, which are the descendents of the original bacteria that combined in the original eukaryotes.  That is why mitochondria have their very own DNA even thought they reside in our cells.

Many thanks to my mad scientist husband for suggesting Dr. Margulis as one of History’s Hidden Heroes, and for staying up late into the night patiently trying to explain endosymbiotic theory to me despite the fact that my grasp on cellular biology is limited to a vague idea that biological organisms consist of cells.  Also thanks to the ever-reliable (Ha!)  Wikipedia article on Dr. Margulis for supplementing the science lecture with dates and things.