Are humans intelligent? Hmm not sure we are, but in comparison the just maybe
As I wrote somewhere early in this discussion, one cannot sensibly talk about "What is AI" without first deciding/defining what we mean by "intelligence" - and that question, which is almost a philosophical one, is very far from straightforward.
If one goes back a long way in time, I think that many/most people would have said that to undertake highly complex mathematical calculations rapidly and accurately required an appreciable degree of 'intelligence' - but the advent and evolution of computers (even calculators) rather put paid to that sort of thinking.
Much more recently, it's not that long ago that tasks such as playing chess at a high level, translating from one language to another, rapidly determining the best route by road from A to B, improving the quality of images, undertaking welding accurately etc. etc. etc. would have been regarded as requiring considerable degrees of 'intelligence' - but, again, computers are now able to do all those things at least as well/quickly as humans, by approaching the tasks is a purely ('programmed') mechanical ('algorithmic') fashion.
Much more generally, the behaviour of some very lowly members of the animal kingdom (e.g. ants, bees etc. etc. etc.) could be thought to demonstrate what we might traditionally regard as 'intelligence'.
The common feature of all of these things that traditionally would be regarded as 'requiring intelligence' is that we are gradually coming to realise that they can be achieved by 'dumb' mechanical/algorithmic processes - and if one believes in a 'deterministic' world/universe, that would eventually come to apply to everything that happens in the world/universe - so the relevant question might actually not be so much "what is intelligence?" but, rather, "is there such a thing as intelligence?".
Whatever, I feel sure that we are going to continuing to see tasks which we have traditionally regarded as "requiring human intelligence" being done 'algorithmically' by machines that are doing no more than what they have been designed/programmed to do.