Ancient brewing techniques

I'm interested in how ancient people brewed beer and after doing some research I have not been able to find how the yeast they used was actually produced. I know it's possible to create yeast by letting fruit like raisins ferment in a jar with water for a few days. I'm wondering if it would be possible to simply pitch that yeast liquid into the wort like you would normally do with a packet of dried brewer's yeast. Obviously it wouldn't be as efficient as commercial grade brewer's yeast but people have been brewing long before modern lab techniques so it must be possible. Any thoughts?

Open fermentation was one. Using fruit skins/raisins, like you mentioned. Yeast sticks were common; at the end of fermentation brewers would dip sticks in the trub, hang the sticks to dry, and on brew day dip those into the wort. They would store them and re-use them. I also wonder if there was yeast present in the Bappir bread that was used in some early brewing. Some yeast surviving the baking process and fermenting the wort, possibly on the dates and fruit in the bread itself.

You might find this interesting.

The Yeast of the Ancients
(It's kinda new agey, but has some interesting info that could provide hours of interesting googling.)

Why brewing ancient Egyptian-style beer is so popular & how to make it


The maltose falcons had a great article on brewing with Bappir, but it looks like they're redoing their site and the old links don't work.

Found it http://archive.maltosefalcons.com/recipes/20051002.php

I shoudl have given you enough to further your google adventures.