Which came first:

the cement sidewalk or chewing gum?

I thought about this this afternoon while I sat at a table outside of an ice cream shop. I was looking around at the cement and noticed oh so many irregular black stains on the concrete. Each one was unique, and represented an individual wad of spent, cast away bubble gum. So many! So much history! These smears and stains seem to last as long as the concrete does.
Was there ever a time when concrete walkways were relatively pristine, and free of gum smears? How recent is this epidemic of gum graffiti? Was there a crackdown on this sort of litter shortly after chewing gum was invented and people started to notice the problem? How quickly did it get out of hand? Or have cement sidewalks always been this way, the invention of chewing gum having preceded the sidewalk?
When I think about cement, I think about the Greeks and the Romans. I believe that one of them created it, so cement walkways have probably been around since then. As for chewing gum, I don't know when it was invented. I think in the 1900's. Maybe in the 1800's. I believe it's much more recent.

I decided to do some research when I got back to an internet connection, and this is what I found:

Concrete, as we know it today, was patented in England in 1824 by a man named Joseph Aspdin, and is called portland cement, although the Romans used something in their structures that was very similar to that.

The ancient Greeks chewed a gummy substance called mastiche, which was derived from the mastic tree. The first commercial chewing gum was not produced until 1848, in the state of Maine in North America.

Portland cement began to gain popularity in Europe in the 1850's, but was not manufactured in the US until the 1870's.

The sort of sidewalks that we have today began to appear in the 18 and 1900's.

Conclusion:
It appears that concrete sidewalks began to be crafted in the 1800's, which is also when chewing gum began to appear as a mass produced product in modern society. They seem to have a nearly tandem rate of growth. It seems likely that the occurrence of gum-spotted concrete walks grew along with the implementation of concrete walks so gradually that it was never really recognized as a problem. There seems to have never been a pristine era of gum-free cement.
Even the Romans may have faced the problem of scraping chewed and spent mastiche wads from their cement creations.
In dealing with this question, there seems to be only one apt analogy for me to use:

The chicken?
Or the egg?