Well, in many instances the primary source material we have for initial Western contacts with ethnic groups in Africa, the Americas, and the Pacific refer to th

Well, in many instances the primary source material we have for initial Western contacts with ethnic groups in Africa, the Americas, and the Pacific refer to them as "primitive savages" or "unthinking brutes," and historically, such peoples were generally regarded as sub-human by many of the Westerners most familiar with them. So if a lack of consciousness on the part of those not previously contacted by Westerners is something that seems possible to you, then these might be the sources of evidence you were looking for.