You're probably not too interested in what some people call ABC gum—already been chewed.

But for archaeologists,such gum—as long as it's really old—is a genetic gold mine.

"It's a bit like Jurassic Park."Natalija Kashuba, a graduate student in archaeology at Uppsala University in Sweden.

She's referring to that famous clip from the movie, about how Jurassic Park scientists extract blood from a mosquito trapped in amber,"and bingo,dino DNA." Except in this case it's human DNA, and it's trapped not in amber, but in exceptionally old chewing gums found at the site of an ancient hunting and fishing village on the west coast of Sweden.

The samples look just like chewed-up wads of modern-day gum.

But don't think Wrigley's—this detritus is black,sticky tar distilled from birch bark.

Kashuba has tasted modern-day versions and isn't eager to try it again.

"Not unless I'm paid for it."So why chew something so unpleasant?

Maybe because their gum wasn't for fresh breath.

"You could use it to seal your boat,or like seal your pots ...