Dear Isinglass - How Are You a Thing in My Beer?

Even allowing for the fact that much of what we know about topics such as medicine and longstanding popular commercial products was the result of old-timey people saying "I wonder what this does. Death? Okay, then let's not do it quite like that anymore. How about when I do this?", getting from a fish to its bladder to use of said bladder in clarifying beer seemed like a huge leap. Like how many other things were people dumping in beer before they got around to thinking of drying a fish's bladder and then tossing it into beer?