Why Did This Take So Long?
So, seriously…we are just now generally realizing the importance of gut health? And, still, the Prevailing Pseudoscience is mostly disinterested.
The microscope was invented in 1590. Poop is pretty easy, if not attractive, to sample.
But, you know, there were poisons to be administred, and lots of diabetic amputations to do, and the Pseudoscience (Never a science of health, remember) never got around to it. There’s no money in healthy people, as George Carlin pointed out.