This might sound naive, but isn't the easiest method to reject the hypothesis is to gather data on gut bacteria in people with ASD and those that don't? Wouldn'

This might sound naive, but isn't the easiest method to reject the hypothesis is to gather data on gut bacteria in people with ASD and those that don't? Wouldn't that be much more direct and explain much more? Or is there some sort of technological or cost limitation to this method?