birch bark was used as a chewing gum and a glue for affixing arrowheads to shafts, the prehistoric chewing gum was made by simply heating birch bark.

 http://dsc.discovery.com/news/2007/08/20/ancientgum_arc.html?category=archaeology&guid=20070820151500  

very interasting I thought. did anyone now this?

Never heard of using birch bark tar, but have heard of using pine pitch for the same reasons.

it also helps with infection in the mouth.

Yes - I did know this before and I received an e-mail from a scientific newsticker yesterday and read the same story in our lokal newspaper today - but it's not a new discovery - even if it is now "sold" like such.
Chewed Birch tar with molar teeth molds/imprints were excavated long ago in neolithic settlements at Lake Constance (Bodensee) for example.

"worried about fossilized poo"
THAT whould have been really interesting. I've several of so called Coprolithes laying here. Any smell gone since millions of years  :D