I still don't think we've proven that at all. Unless you believe in god, then no one has ever "built" an intelligence. The human brain is the result of millions of years of evolutionary pressures.
Regardless how it is created, if it exist it can be made artificially again - it is just matter of time.
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.
