Goliath predates bananas. They have no validity as a measurement in this circumstance.
TIL that both football and Oliver Smoot’s fraternity pledge predate bananas.
Bananas were apparently first cultivated 7000 years ago, so I’m afraid, based on Biblical chronology, that Goliath post-dates the banana (which predates the creation of the universe) and thus a banana for scale is a valid measurement for his height, as it is the standard reference for scale according to science I just made up.