Aside: My first encounter with Margulis’s Serial Endosymbiosis Theory blew my mind.
I’d go so far as to say that SET changed my worldview. I’d always looked at evolution solely through the cold, brütal lens of selective pressure and competition.
SET showed us, however, that symbiosis (i.e. fundamental cooperation) is right up there with competition... kind of a countervailing force within the story of evolution.
I don’t know why, but I take great emotional comfort in that. Perhaps, being non-religious, it allows me to see something humane(?) encoded in the rulesets that govern change.
My rule of thumb is whether or not you get your name attached to some physical phenomena. ie: Newtonian Physics, Hawking Radiation, etc.
That's a fair yardstick
If we put Sagan with Darwin we should not forget to add Margulis to this list also.