The Evolution of the Immune System

Do the advent of immensely complex immune systems prevent a huge broad branching evolutionary event like the mitochondria symbiosis from happening again? That's a great question. I don't think so, but I think we also should be a little bit cautious. There's some balance there between not killing yourself, but recognizing something foreign and sort of getting rid of it if it's weighing on your own replicative success. The immune systems or the sort of the biological sophistication is modern. They've had just as long sort of evolve as we have.