why do they break down the ‘hard-to-digest parts’?
The only explanation I have to offer here is a selection effect. Mostly when something is food to us, other creatures compete with us for the food and we want to ward them off. Occasionally we find something that transforms nonfood to food, and encourage it to grow. Crops are one example. Ruminants are another. The microbes that grow on grain are another.
Is there an implicit statement here that water broke down the hard-to-digest outside parts and brought the yeast molecules in?
It’s the breaking up of the wheat kernel in grinding flour that makes more of the energy available (vs the occasional leakage you might expect to happen without human intervention), by opening up the capsules it’s in. But water is also needed for metabolism, so until you wet the flour the naturally occurring grain-eating microbes can’t take much advantage of this.
The only explanation I have to offer here is a selection effect. Mostly when something is food to us, other creatures compete with us for the food and we want to ward them off. Occasionally we find something that transforms nonfood to food, and encourage it to grow. Crops are one example. Ruminants are another. The microbes that grow on grain are another.
It’s the breaking up of the wheat kernel in grinding flour that makes more of the energy available (vs the occasional leakage you might expect to happen without human intervention), by opening up the capsules it’s in. But water is also needed for metabolism, so until you wet the flour the naturally occurring grain-eating microbes can’t take much advantage of this.