"But we'll never know! They'll end up debating it for centuries to come, there'll be a journal devoted to that issue alone, but we'll never really know."
"If it's too close to tell, it's probably Terran," John said, grinning at the boy. "Anything that evolved separately from Terran life would give itself away in an instant."
"Probably," Ann said. (5.8.121-123)
Probably can be an awful word sometimes. Case in point: it can be pretty awful in science when you just can't really know. On the other hand, we imagine all those professors snagging tenure by writing essays for those journals think probably is just hunky-dory. And we do love us some professors.