People sometimes doubt that animals are conscious. Here’s some evidence about parrots. According to these two articles, parrots eat sap from opium poppies until they are so stoned they fall out of trees.
Why do parrots do this? Probably because they like the way it feels. In order to enjoy a feeling, or enjoy anything, they must be conscious, just like they must be conscious in order to feel pain.
I think it’s likely that consciousness existed before life. Natural selection created mechanisms by which organisms make use of consciousness, but natural section didn’t create consciousness.
I speculate that pleasure and pain are the first uses to which consciousness was put in the history of biological evolution. They constitute a mechanism for attraction and aversion. Those functions exist even in one-celled animals, although I’m not suggesting that consciousness is present in them. But who knows? We assume that consciousness requires a nervous system, but we don’t whether that’s true.
The carrot-and-stick mechanism of pleasure and pain, which is dependent on consciousness for its operation, has probably been conserved for a long time. It would be interesting to know the simplest organisms in which it operates.
When I was about four years old I cut an earthworm in half while digging with a shovel. It wriggled frantically and I thought it was in agony. Sixty years have passed and I still think it was in agony. I cringe when I watch people impale worms on fish hooks.
These torturers of earthworms apparently think that because earthworms are dumb, at least compared to us, therefore they aren’t conscious and therefore they can’t feel pain.
This reasoning is wrong. Consciousness and intelligence are no more closely related than consciousness and pain or consciousness and pleasure or consciousness and fear. Consciousness came first, and it exists even in the absence of intelligence.
By the way, parrots are pretty damn smart. I used to know one, a female Amazon named Laura. She was quite a character.