I've had precursor archaeology sites spawn on the other side of a marauder empire, and then the AI empire on that other side went and did it long before I could punch through. I really dislike the archaeology-chain precursors; even if they're not blocked off by a FE or something and rendered uncompletable, they still tempt me towards expanding in ways / directions that might be overextensions / indefensible, and then unlike the anomaly precursors, there's no "spend minor artifacts to get progress later" mechanic to catch up if you got unlucky in the earlygame. Whenever I get Zroni or Baol, I basically accept that there's a 30+% chance that I'm just not gonna get to finish it.