A friend of mine is a farmer. He supplies all kinds of meat to butchers in the local area, except pig.
I wondered why, and he told me that after he had kids he decided pigs are about as intelligent as a 3 year old, and he simply couldn't bring himself to kill them anymore.
Hmm, I've been around farm animals all my life, and if your criteria for not killing them is basic intelligence, many of them are well past that line. I'm not sure about 'intelligent as a 3 year old' as in many ways they're both smarter and dumber than that. But you can't hang around any of these animals and pretend they aren't clever.
Interesting how we tend to value life based on intellectual capability. I suppose its an emergent effect of our human-driven empathy.
You could make the argument that being an omnivore is the most "moral" standing (excluding climate effects), as it does not value life based on its similarity to us. It holds life to have intrinsic value.
It's not that novel or different from how we treat each other nowadays. It's not empathy. Intellectual capability determines the value of your contributions to society thus your value as a person. Bravery and stupidity disguised as "courage" were the virtues determining your worth in middles ages, now we check the intellect. Intellect tells us how valuable your life is, and intellect is what some people (e.g. politicians) are so good at faking.
This is my personal view, but that is nonsense. I understand intelligence is not all these things, but 3 year olds can follow instructions, do pretty advanced problem solving, speak, do basic math, understand logical problems. I'm sure you can find some aspect where a pig and a 3yo are on the same "level", but as a general comparison, it absolutely fails.
I think it's impossible to compare human and animal intelligence because there's a "hard-coded" part to intelligence. I don't think being unable to understand human language says anything about the general intelligence of a non-human animal since humans are at least partially hard-wired to understand language.
That pretty much precludes any animal from ever being able to "follow instructions", "speak", "understand logical problems", etcetera. Even if they would have the general intelligence to do the things we want them to do, it's very difficult to encode that information in a way that they would understand.
I wondered why, and he told me that after he had kids he decided pigs are about as intelligent as a 3 year old, and he simply couldn't bring himself to kill them anymore.