Birch Bark Adhesive

I was playing with fire this week trying to replicate a prehistoric adhesive. There was an article last year that Neanderthals were attributed with making the first glue, as far back as 200,000 years ago, from birch bark.  Archaeologists assumed it was too complicated for primitive man to make without ceramics, but found several other methods that proved its feasibility.  Birch tar was found hafting Neanderthal spears.  The first method involved burying rolled bundles of birch bark in ash, and then covering with embers.  Tar was scraped off the bark rolls.  The second technic involved putting embers directly on the rolled bark, suspended over a pit to collect the oil.  In the third, a container is placed in a pit, covered with birch bark, then dirt.  A fire is built on top of it.  All produced amounts of birch bark oil for the scientists.  I tried variations of the above, and was unsuccessful, only consuming the bark.  My fires were too hot, too long I think.  With my last amount of birch bark I relied on the conventional way and put the rolled bark in a sealed canister with a hole in the bottom.  A fire was built around and a small amount of oil dripped thru the hole into a can below it, buried in a small hole.  I did manage to produce a small amount of birch oil.  This then required a few hours, over low heat evaporating the volatile oils, to make the sticky tar adhesive.  I need to work on this more, but it was a valuable learning experience.  I had purchased some birch tar on Etsy to have an example to aim for.  I have a book from 1961, ironically showing rolls of birch bark dripping tar while spears were being hafted with it.  Doesn’t quite work like that. But, it is probably the best adhesive/filler I’ve worked with...super tacky, like sticking your fingers in epoxy.  Unfortunately, birch trees are more ornamental in Nebraska than farther north.