Beer and bread, and the yeasts used to make them, used to be indigenous to the region, and sometimes very localised. Every brewery and bakery had their own local yeast cultures. The rise of factory bakeries and breweries meant nearly all of those died off. IIRC industrial brewing depends on just 3 or 4 strains of yeast. Only the relatively recent resurgence of craft baking and brewing has kept some of the others around.

The local strains that led to so many wonderful tasting breads and beers have been lost.

I'd be as interested in learning how the local strains of yeast have changed over those intervening 4,500 years, as seeing he a good result trying to bake from what he retrieved.