It is simple, as ant cannot contain human, in the same way humans won't be able to contain AGI. Can it exist, yes it can - simply, can me and you think, yes. In a way we are "device", so therefore, it is possible to make intelligence similar and/or more powerful than our is.
I mean, yes, I can have a child and raise her to be smarter than me, but I don't really think that's what you have in mind.
The strong AGI proponents always resort to hand-waving and dubious analogies. There's no reason to think that building ever-larger ML models will produce an intelligence capable of comprehension and insights like a human mind unless you believe the human brain is nothing more than a bunch of weighted vectors.
Same as with bacteria. 'In May 2019, researchers, in a milestone effort, reported the creation of a new synthetic (possibly artificial) form of viable life,' - https://en.wikipedia.org/wiki/Artificial_life
Give human enough time and resources, we can replicate anything, that is in our nature.