"...an early genius of military engineering, Gabriele Tadini." But more than 1500 years before him there were others such as Archimedes and Caesar.
I wonder if Tadini was a polymath similar to other great military engineers like Archimedes and Leonoardo who would have been living at the same time as him.
For example knowing about plants and animals. We as whole humanity are still far from knowing them all on the earth, so how could somebody from history knew them all?
And even if you only count "everything" as the whole current knowledge of humanity, then also no, as there are for example tribes in the jungle who know about plants or hunting technics the genius in europe never heard of.
I've heard this question before. I think it's more useful to think of it as "When was the last era when it was possible for one person to know everything that's known?"
Doubtful that there ever was such a particular person, at least because of geography, as you point out, and different concerns in different parts of the world. But there must have been such an era; I don't know when that was.