So then the samurai chatter makes them a brother. It's been shown to be organized, rather than just nervous jibbering, and to hold to some consistency. Language is as language does....
And, or course, until humans become relatively fluent in even one other species language, even the aforementioned turtles, we'll never know the level of abstraction, perhaps a greater indicator of higher intelligence and a creative mind, a species might command.
In regards to the creation of fire as an indicator of humanity, should a sasquatch watch a human use a lighter, and then later obtain one and figure it out(providing its not one of those sasquatch-proof lighters) and then use it to light a contained fire, would that count towards its humanity?
And lastly, while, in a sense, its a necessary evil, I see you guys putting a lot of faith in taxonomy, as a near monolithic truth. But really, all it takes is one grad student (ok maybe more than one, but you get the idea) looking for a really killer dissertation topic to screw the whole current set up. Subspecies become species, genus gets divided up and renamed, what was once a separate species turns out to just be a juvenile form, a tooth from a Chinese apocathary(sp?) turns out to be just a big orangutan. But I guess the point is Taxonomy is a dynamic system in constant, if not rather slow-paced, flux, and changes in proximities and "associations" are ongoing as further evidence come to light. What is Homo today, or was sapiens yesterday, can find itself reclassified in short order (though I'd hate to be the fellow trying to defend the renaming of Homo sapiens to a panel of physical anthropologists!)