I happen to have a textbook that has some citations for the incidence.

Kinsey and colleagues found 8% of men and 3% of women did it at least once, and 17% of men raised on a farm (all self reported). This was in the 50s, but more recent studies have also found that a fair number of people have done it at least once. The large majority only did it once or a few times, often as a dare, initiation, or out of curiosity. And clinical zoophilia (where it's the primary means of arousal) is extremely rare and usually has a lot of comorbidities.

It doesn't happen often, clearly, but the research we have suggests that it's common enough to where you almost certainly have met someone who has done it.

but there's a lot of fictional depictions of bestiality, a million lurid rumors and taboo tales. makes you think it's more common & possible than it is, but there simply never were 'donkey shows' or bestiality executions in ancient rome.

You, uh, got like any evidence to support a negative?