Maybe I used a very bad and distracting (and political) example. "Suffering" wasn't really something I was trying to talk about, here. (To be clear, pain is a matter of instinct, which is to say, a predefined brain structure that "works" from birth—and maybe before-hand—whenever it shows up.) Rather, I was specifically talking about this thing we call "thinking." The thing that humans do when they're awake and lucid, and don't do when they're asleep/unconscious/in a dissociative fugue. The thing that the courts care about as mens rea.

Many higher-level vertebrates develop some capacity for "thinking"—that is, for planning/strategizing, puzzle-solving, learning and synthesizing information, forming concepts and abstractions, overriding instincts with beliefs based on evidence, etc. Humans and all other primates do this; as do crows and their relatives; as do dolphins; etc.

But none of these animals start with that ability from birth. "Thinking" has never been observed as behavior available instinctually to any animal. A newborn crow or gorilla, despite being rather self-sufficient with a library of instinctual responses, won't be able to solve the puzzles that we get the adults of those species to solve and which we cite as proof of their intelligence. They grow that ability from months/years of life experience.

In fact, almost by definition, "thinking" is something you have to build: it's a big conceptual hierarchy with sensory data at its base. And—as far as we know—instinct can't pre-bake the needed raw sensory data into brains. (It can bake in higher-level associations, like scent- or pattern-associations for predator avoidance. But it doesn't include these in low-level "raw" terms where a brain can derive any of its own interpretations or abstractions from them.)

Without accumulated experience, a brain is still experiencing the world, and reacting to the world, and experiencing reward signals from the world—like most animals do—but is not yet thinking about the world. Thinking is a matter of updating beliefs about schemas/models/concepts; and those things only exist when derived from sense-data "evidence."

Thanks for sharing your thoughts. I recently had a discussion concerning animal sentience and was having trouble articulating my thoughts. You have managed to concisely convey "thought" in an eloquent fashion.