Science says that it isn't a fact.
It turns out that no, it does indeed say that it is a fact.
Of course, this being science as opposed to dogma, it might conceivably be revised in the future. The odds are rather slim, though. Once again, a comparison with gravity will be useful: one might imagine a possible future scenario where one finds out that celestial bodies do not exert attraction towards each other... but given how consistently the current understanding of grativy has been demonstrated in actual observations, that is very much only a theoretical possibility.
One could find out that common descent only "seems " to be a fact. But only in that same sense that one can doubt that, say, the sun does exist as a physical entity as opposed to some sort of clever illusion.