I just found this from a site on Victorian children and weaning. It’s quote from a Victorian book. They do advocate mush as a first food but…
The practice of giving thickened food to infants at too tender an age is a source of endless trouble, as before observed. In one of Dr. Edward Smith’s admirable articles on dietary he remarks that the feeding of young infants on bread, flour, biscuits, and other substances than milk, is a “constant source of derangement of the liver, and a frequent cause of fits.” However considerable the quantity of such food passed into the stomach of a young infant may be, the body is not thereby nourished, but irritated. A babe, like an adult, is only nourished by what it has power to digest.
As a general rule a babe ought to be entirely nourished on milk until the first tooth appears. Even after that period milk should for a considerable time form the staple article of food. Larger quantities should then be given, and greater intervals between the meals observed. It is estimated that a babe three months of age will consume at least three pints of milk in twenty-four hours.
“Up to six or seven months of age,” Dr. Letheby says, “infants have not the power of digesting farinaceous or fibrinous substances.” After that age many descriptions of farinaceous food may be used, and are to be strongly recommended.
So even the good old Victorians knew that early weaning caused digestive problems!