That's a good point, although it would be hard to argue that the cats weren't likely eating some human food waste just as they do today. The Egyptians, where many argue wide-scale cat domestication is likely to have occurred, fed their cats on bread and milk and slices of Nile fish, and certainly considered cats not only pets but family. In addition to finding some wealthy mummified with their cats, a specialized cat tomb was found with approximately eighty thousand cat mummies where the Egyptians laid their loved ones to rest at approximately 2000 BCE.
Here from 1876 was a resident 'cat expert' Gordon Stables:
"If then, only for the sake of making more valuable as a vermin-killer, she ought to have regular and sufficient food. A cat ought to be fed at least twice a day. Let her have a dish to herself, put down to her, and removed when the meal is finished. Experience is the best teacher as regards the quantity of a cat's food, and in quality let it be varied. Oatmeal porridge and milk, or white bread steeped in warm milk, to which a little sugar has been added, are both excellent breakfasts for puss. Remember that too much flesh-meat, especially liver,—which ought only to be given occasionally,—is very apt to induce a troublesome diarrhea."
I don't think modern nutritionists would agree though!
