[mcbits]

I think written language is our primary difference. Prehistoric wild humans had spoken language for hundreds of thousands of years, but we didn't have the explosion of "intelligence" until the advent of written language ~5,000 years ago.

Or in more general terms, we have the ability to use our environment as a durable supplemental memory. This is what I would look for in assessing whether another species has the potential for human-like intelligence.

[bonzini]

While I agree in general with what you wrote, there are examples of orally preserving collective memory. Think of the ancient epic poems for example.

Painted or etched drawings on cave walls came long before writing, and no other existing species on Earth does that except if we teach them.

Non-homo species also do not domesticate fire. Fire means not being afraid of something that you usually have seen only in scary situations, and it can lead to writing tens of thousands of years down the road (papyrus happens to preserve well in a pyramid in the desert, but cooking clay tablets or melting metals works better everywhere else).

[thaumasiotes]

> Fire [...] can lead to writing tens of thousands of years down the road (papyrus happens to preserve well in a pyramid in the desert, but cooking clay tablets or melting metals works better everywhere else).

I feel pretty safe in saying fire had no direct influence on the development of writing anywhere. Chinese characters first show up carved into bones. (They are well-developed at this point; obviously they originated some other way. But we don't know how.) Cuneiform tablets were originally unbaked; baking for preservation was an innovation that happened long, long after writing was established.

And the difficulty of working with metal means it is totally unsuitable as a writing medium. Although particularly important cuneiform documents (peace treaties) were sometimes cast in metal, only the final draft would be -- as the treaty was "in negotiations", messages back and forth were in clay. A society that can only write on metal is a society that will never develop writing in the first place. There is no reason other than wishing to impart a ceremonial permanence to write in metal.

[milquetoastaf]

>Or in more general terms, we have the ability to use our environment as a durable supplemental memory.

You mean like how some species of nut-hiding birds can hide over 20,000 nuts in distinct locations comprising several square miles of territory and then recall precisely where they are when necessary?

[mcbits]

That points to a well developed individual memory. I don't think they're using the locations of nuts to encode knowledge for each other and future generations. (If they are, that's tremendous.)

But imagine if the birds also carved symbols into tree trunks and taught their friends how to interpret the symbols to find hidden caches of nuts, or to share techniques for building more durable nests, etc.

Written language allows us to store, access, and share information beyond our individual memory limits. It is sort of a collective memory as well as an expansion of individual memory. I can write down the locations of 21,000 nuts, and I can hand that book off to you.