The problem is, conflating theories (beliefs really) with truth is one of the things reproached to past religious people. There's no shame in saying: "we don't know for sure, but this is reasonable so far".

If we don't, then we're sowing the seeds for discord for when our theories will need to be updated. And it's reasonable to think that they will, as, so far, most (all?) scientific theories has evolved.

IIRC, Darwin's views on evolution require patching e.g. to take into consideration chaotic incidents affecting mortality/genes propagation (e.g. asteroids, epidemics).

Maybe if that theory keeps accumulating patches, it'll end up very different from where it started!