OTOH, human brains are primate brains just as and not more evolved than other primate brains. Did we build on sign language our ancestors already had, or did evolution make a magic jump to human sign language?
You don’t need to consult a cladogram to realize that gorillas’ ancestors split from the gorilla-human common ancestor at the exact same time that humans’ ancestors did. That’s the definition of common ancestor.
Or, of course, you could measure “how evolved” a species is in number of generations, instead of in number of years. By that standard, we’re probably the least-evolved animal on the planet, because we have generations so much longer than everyone else’s.
I was thinking in terms of ‘common primate ancestor’, where different primates branched off at different places. I don’t know where we and the gorillas fit along those lines, though probably in a different place than we and the chimps separated, as we’re more closely related to the latter. And I don’t have time to look it up just now, but I’ll try to remember to after work, because I’m curious.
I still don’t understand the distinction. At our most recent common ancestor with the gorilla (which was, of course, a primate), the ancestors of both species branched off. It’s not like there’s some “main primate line” that stayed straight while various species branched off from it. Now, the ancestor of humans shortly after that split were not humans, but then, the ancestors of gorillas shortly after that split were not gorillas, either. I suppose you could ask whether that most recent common ancestor was more similar to humans or to gorillas, but then, you have to define what you mean by “more similar”: There are probably some traits of that ancestor that we retained but gorillas didn’t, and some that gorillas retained but we didn’t.
It depends on what traits you base the cladogram on. For instance, if you use gene patterns, the ‘chimp group’ and the ‘gorilla group’ branched off off the homonid root, both with 48 chromosomes, and then the ‘human group’ branched off the chimps through the fusion of two chromosomes to make 46.
http://www.indiana.edu/~ensiweb/lessons/chr.clad.prim.pdf
In any case, the human/gorilla split is much closer to the modern groups than to the original primate ancestor, us both being on one branch of the Hominidae, as opposed to, say, the gorilla/orangutan split with them being the other branch, or the gorilla/gibbon split with them on a line branching before the Hominidae, or the gorilla/new world monkey split much farther back, which was what I was getting at but apparently expressing poorly.