humans and primates have a common ancestor which is still unknown.... which does not exactly mean humans evolved from monkeys.
yes there's no doubt in my mind that the head was so small because it was re-carved by the egyptians. what was it originally? who knows. in reality it could even have been just a giant statue of a lion rather than some mythical creature! but i don't think the egyptians created the original work, personally. it just doesnt seem to fit, even if they ARE known for their gigantic monuments. as for the pharoah being blotted out from history, i'm not sure how often that happened. i'm not too well versed in egyptian history (particularly politics) but i personally know of this happening only once, when hatshepsut (the first female pharoah, who dressed and is depicted as a man) died and her name was stricken from most records and some of her monuments defaced, literally. if this happened in a more extreme manner or multiple times, i'd gladly welcome some information you could pass on to me. its nothing of tremendous value to know, i suppose, but it does interest me.
