We are all descended from the same species. That species was not a gorilla, or a chimp, or a bonobo, or an orang-outang. It was another species entirely, which splintered into several distinct groups. Each group evolved in its own way; one group became gorillas, another group became humans.
It's to do with terminology and phraseology. Is the common ancestor of all apes (which includes us) an ape? Or a monkey? Or what?
If the production of heat were the only criterion for starhood, then you would indeed be a small star.
Lots of animals are sentient. Dogs, cats, whales, dolphins, apes, etc.
Take your pick:
Genetic profiling of Homo, Pan, etc, and the fossil record, mostly.
Hah, now that's a question and a half. Sentience generally means concious, the ability to experience qualia (pain, pleasure, the colour 'red', etc), etc.
Take your pick:
'Homininae', for example, is the name of a species or line of species that once lived, but eventually split into Hominini and Gorillini
Genetic profiling of Homo, Pan, etc, and the fossil record, mostly.
Well if you define it as being unique to humans, then of course humans are the only ones with it.
How do you know? Certainly, they don't experience things in exactly the same way we do, but they can also experience things we can't. Bees see in the ultraviolet, ravens can instantly count higher than us (we can 'see' when something is made of one, two, three, four, or five items; higher numbers have to be counted directly), etc.
Sure, but does that make us sentient?
As far as I know, it was inferred to exist from the evidence. But it could be that there's direct evidence of its existence.
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