When I was at college I was fortunate enough to become acquainted with Lynne Margulis, one of the pre-eminent scientists of our time. Margulis is known for the Theory of Endosymbiogenesis. In short, this is a theory that describes how the complex life-forms on the planet were formed from much simpler ones – single-celled creatures that, by one means or another, fused, physically and in most cases genetically to a predator, host, or symbiont. The chloroplast of plants were once free-living single-celled organism. Mitochondria were also. The undulipodia that propel living things were once spirochete bacteria that were slowly incorporated into larger, more complex organisms over millions, if not billions, of years.

When I was studying immunology I was amazed to discover the vast array of different immune cells that live in animals like us. Among the most interesting were neutrophils – a type of fast moving cell usually among the first to show up at a site of infection. I was struck by how determined they seemed to be to catch invading bacteria, almost as if they were in a predator-prey relationship. In a microbiology class at UMass, Amherst I learned about viruses, and I wondered, “Does anything in nature actually eat viruses?” This reminded me of the theory of endosymbiogenesis; the huge number of different immune cells, each with their own specific jobs, came to resemble a population of creatures that once lived external to us but had somehow become incorporated into the animal genome. And what of their prey, the various microbes they guarded us against? Did they once live independent of hosts? Did the infectious bacteria adapt to life in hosts first, and were followed inside by their natural predators? Is this how the immune systems of higher life-forms came to be? Is there anything out there that eats viruses, other than immune cells?
I just found this interesting film of a neutrophil chasing a staph bacterium and it triggered the memory of endosymbiogenesis – and all the secrets yet to be discovered about this most fundamental aspect of evolution.