They are somewhat similar structures, because they have to do the same job, and the job requires that sort of structure. They are not compatible in that you could put a bat wing on a bird, it would be rejected as foreign tissue.
Arboreal? What do you think that word means?And that would have been entirely fine. Baboons are still arboreal and omnivorous, they still have bilateral symmetry, sexual dimorphism, grasping appendages, vocal capacity, social structures, etc. For the purpose of this experiment it would not have mattered what exact species the "humans" ended up being.
Baboons live on plains, or on mountains, not in forests.
Dolphins can't use tools. It's barely possible that there are intelligent cetaceans, but they aren't human whether they are intelligent or not.They probably won't, not without being pressured to do so. Life tends to reach an equilibrium with its pressures and stay there. And even if, say, coconut crabs could evolve into a society, surely dolphins would have beaten them there. It's not about what species could become intelligent, it's about what species is the first to do so. In an Earthlike environment, with an oxygen atmosphere, sunlight, and a variety of tall and short plants and varied other animals, an omnivorous, endoskeletal, arboreal creature capable of tool use, is likely going to succeed the fastest, simply because it can make use of all kinds of foods, can move around freely to locate food sources/shelter, and once tool use begins the evolutionary pressure of the remaining surrounding threats drives it to come up with better tools to compensate for what remaining weaknesses it has, thus improving its intelligence further and faster.
That's the entire difference between humans and other peoples, other peoples also being known as intelligent aliens. I've no problem with fictional aliens, it's off-Earth originated humans that are completely ridiculous.Humans as we know them exactly, are an accident. Humanoids in general, are just the result of a particular kind of environment and a few lucky rocks.