You could restate the golden rule as "treat others sufficiently like myself the way I'd like to be treated", not so long ago this wasn't applied to other humans

You could restate the golden rule as "treat others sufficiently like myself the way I'd like to be treated", not so long ago this wasn't applied to other humans who didn't look the same, but now it just seems reasonable to expand who the golden rule applies to beyond just species into... beings within a certain threshold of human intelligence. It is somewhat of a fundamental of morality, beings which are sufficiently intelligence deserve the same rights as I want for myself. If you remove intelligence (or something quite similar) as the criteria, what do you have instead?