slaves were not merely treated as more intelligent cattle

While a very few slaves were fortunate enough to have humane masters who treated them...not as equals, but at least as human beings, to conflate the treatment of a tiny group of house slaves with ancient slavery as a whole is totally erroneous. By far the majority of slaves in the ancient world were not house slaves, they were agricultural slaves. Cato's opinion that field slaves should be locked up at night in underground dungeons and that sick slaves should be fed less was not the exception in treatment of these unfortunate individuals, it was the norm. Field slaves were generally captives of recent wars, defeated soldiers and other able-bodied males with no education and little physical attractiveness. They were brutally treated and had extremely short lifespans, as new labor was constantly available through the constant capture of military captives. And the majority of house slaves were not particularly well treated. For every Tiro there were thousands of slave boys and girls sexually abused or badly beaten by their masters, and even in a household where a few highly prized slaves might be treated well there were still dozens of other slaves doing menial labor whom the master might not even know. The very best masters might have made an effort to behave humanely towards their house slaves--as Seneca reminds us to do--but the law did not. Slaves had little protection under the law, and any familiarity with Roman servile law at all immediately betrays that Roman law saw little distinction between slaves and livestock. The experience of a tiny handful of the hundreds of thousands of slaves that existed in the Roman world at any given time is not indicative of the treatment of slaves, either practically or legally, throughout the world as a whole.