[twirligigue]

Elephants form social hierarchies too (which provide 'value comparison', surely?) and have larger brains than us but still they are less smart, no?

They make vocal calls and signals but they haven't evolved a general-purpose language. Presumably they could have. But they haven't.

Whereas humans did. Language is a huge meme transmission booster and we evolved other boosters such as large sclera so you tell roughly where someone is looking.

I don't know why elephants haven't gone that way. Perhaps because their adaptive niche and lifestyle isn't so dependent on memes to start with. Whereas our ancestors were relatively helpless, physically speaking, and thus utterly dependent on their memes both for survival as well as for social position. Which placed strong survival and sexual selection pressures for improved meme transmission and storage.

People who behaved or even dressed differently were looked down upon by their tribes or social groups and thus were less likely or simply unable to access food and mates. So, you're right, there is a connection between social hierarchy and intelligence. But fundamentally it's to do with memes (see David Deutsch's The Beginning of Infinity, Chapters 15-16).