I would argue that we're neither positive or negative, but simply that we are. Evil and good are human concepts. They're based on our feelings that are primal, specifically pain and pleasure. Pleasure is simply a physical (yes even when you just have "good feelings") reaction to stimuli, and same with pain-- they're only there to motivate you into procreating, or surviving.

AI and robots would not have these by default unless we anthropomorphized them into HAVING such motivations. It's hard for humans such as you and I to actually see a living breathing organism without these motivations because of how deep-rooted and primal they are. They are genetically hard-wired into our brains!

Secondly, we evolved over less than a billion years. Other life is clearly very close to sentience, or is actually already "sentient". There's not a very concrete way to prove that though-- many animals are self aware and pass the "Mirror Test", others clearly demonstrate human-like social structures, and others don't have either of those, but clearly communicate and have unique social structures. Given how quickly we evolved from early primates (only a few tens of millions of years), 4-5 billion years is literally thousands of times longer than how long it took us to reach our current evolutionary stage.

That being said, what I think the essence of what you perhaps meant was that we are CURRENTLY the only chance, but as I said, we are far from the only intelligent creature on this planet. Hell, look at elephants, dolphins, various other primates, raccoons, you name it. Currently as in right now? Yes. Currently on a geological time scale? Heeelllll no. We've only been civilized for what, 20,000 fucking years? That's just... mind boglingly small. Before that, we were barely a step above gorillas, rustling in the trees.

...man that was neat to think about.