The evidence we have now strongly points to that Gauguin cut it off during an argument.
A lot of circumstantial evidence but it's pretty telling. Paul Gauguin was an expert swordsman who carried a particular sword with him at all times. He and Vincent would have terrible fights when they lived together in Arles. We know that Paul was scheduled to move away the next day and that night they had a big fight and that Paul left town immediately in a rush leaving his sword behind. The new evidence that was found recently is a doctor's rendering of the cut ear. It's an extremely clean cut from the top, straight down.
There's more to it but those are some interesting details.
https://www.vangoghmuseum.nl/en/art-and-stories/vincent-van-...
Very sad.
From this we came up with: after an argument with Gauguin, he cut off his own ear and gave it to a prostitute he probably was in love with, which shows how crazy he was.
I mean, now we have the doctor's rendering and it's clearly a sword cut, but couldn't we have figured this out before? Really?
https://upload.wikimedia.org/wikipedia/commons/b/bb/Drawing_...
yeah it's funny to think how much of history is likely to be retold incorrectly