Inventing Zero

The Olmecs have been credited for coming up with the "concept of zero." Well, what does that mean? Surely everyone in every age understood the concept of having "none" or of "all gone", as in "There are no elefants in the room." or "The cookies are all gone."

What's meant is that mathematically, arithmetically, or in a "counting" sense, the Olmecs found the need to use a glyph as a place holder in a number that had nothing in a certain place value. So they had a picture or glyph that was put there. Just like the number, "405" means 4 hundreds, no tens and 5 ones. You can't leave the tens indicator out; it would change the number to 45.

So were they the "first"? Or just the first in their area? Or is it just remarkable that they had such a concept in their system of numbers?

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