Language enables us to do something no other animal can*: remember things after the death of the discoverer. This means that we’re not stuck where animals are stuck, spending a lot of effort and taking a lot of risks discovering, individually, a whole shit-ton of relevant information about the world.
At first, this effect looks marginal, because a lot of animals have more powerful and specific instincts than we do. And it would have been. Things would have moved very slowly. But then we get to “how to use a rock and a stick and teamwork to kill a predator” and shit, you just upended part of the local food chain in an afternoon.
Language allows discoveries (which, evolutionarily, are basically specific behavioural changes) to be propagated on non-evolutionary timescales, giving our rivals, prey and predators no time to respond. That’s how we moved so fast. We’re a natural disaster.
There’s a brilliant set of lectures called The Ape That Got Lucky that postulates mostly how we became linguistic animals, too – very much worth a listen.
https://en.m.wikipedia.org/wiki/The_Ape_That_Got_Lucky
*there are very very weak and specific counterexamples of animals passing on knowledge about specific tasks; that they don’t do so linguistically but by action-copying is relevant here
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