Hogwash. We don't even have a consistent set of ethics on how to treat animals today, in the age of the Internet. We have people who refuse to eat meat because of how the animals are treated, and we have places where the locals make sport out of torturing animals to death, and indeed, our own recent history includes that as well (look up badgering).

Not to mention, the variation in treatment of homosexuals (including what constitutes homosexuality), people of different skin colors, handedness, how rape is treated in various cultures (often tied in with notions of property and ownership of all things), or even the various definitions of rape... The list goes on.

Maybe there's a core there in terms of how we treat a given in-group, but equally important is who belongs in that group and why, and that part seems to be tremendously flexible. Ditto for what constitutes acceptable treatment of outsiders.