But evolution doesn't find optimal solutions in the wild. Invasive species prove that. They were a solution that would have worked but evolution never managed to create locally.
But, like I said, no expertise, just my initial reaction to your comment.
Much like “weeds”, when referring to plants, is a distinction that is only relevant in the context of human agriculture, so it is for “invasive species”. All life is, by definition (reproduction), invasive.
Like I feel like there is an inherent observer bias in the way survival is being defined, it feels more like "observable." Like in the local time of a tree snapshot (from its perspective), time may feel different than from ours observing it.
No, there isn't. There's an ancestor population.
"This organism survived objectively better than any other organism of its time"
No, it did not survive. Being an ancestor is not survival. And this has nothing to do with "optimization" ... if evolution optimizes survival, then your "single common ancestor" predated optimization. You're just throwing concepts together to support a prior belief, but the facts don't work that way.
"I think it's possible to define survivability objectively using a little graph theory."
Maybe you should actually try it. Perhaps then you would notice that your notion of "optimized survivability" is about the future, but you're talking about graphs of the past.
Are you sure about that? Viruses too? (depends on your definition of "living" of course) To clarify: I don't know if there is or isn't, I just don't think anyone does.
BTW this organism is called LUCA. Read: https://en.wikipedia.org/wiki/Last_universal_common_ancestor