How was beer invented? We don't really know.
Making beer is much more complex than making wine. Firstly, after the barley has been harvested, threshed, winnowed etc etc it is still not in a state from which beer can be made! The barley must be malted, i.e. the grains must be wetted and allowed to begin sprouting, then dried to kill it, then heated to about 66C for a while.
We can imagine then, some nomadic housewife with a basket of grain (barley, wheat, oats, rye etc) just gathered being caught in a rainstorm or otherwise accidentally letting the grains get wet. A few days later, the last of the gruel made from the sprouted grains smelling, shall we say funky, but nevertheless being eaten by some Neanderthal lout who a short time later feels like one of the gods, with "hilarious visions clambering in [his] brain." Untill the day after, anyway.
So beer was born. Of course, you couldn't just keep shoving nubile Neanderthals into the rain with a basket of grain everytime her brutish hubby wanted a buzz:-she might club him one night! And he wanted to buzz like a vacuum cleaner, and so did the lout in the next cave over. In fact, the crazy cavemen consigned themselves to creating civilisation. The barley, wheat etc crops needed to be safeguarded and eventually to be planted, and beer making put on some regular footing. And given a god of its own:-always a female god, BTW
So Civilisation was born! What a mistake!
So how did the citizens of the first cities make beer? Bear in mind they had nought but some empirical knowledge, no sanitisers, yeast cultures, insecticides yadda yadda. They made bread! Not just any bread, I hasten to add. Grain was moistened and put into a deep pit to keep it cool. After some days the sprouted grain was formed into loaf form and baked in a low oven. Inside the oven, the wet, sprouted grain would have "mashed" and turned some at least of the starch in the grain to sugars. Some of the baked loaves were then sliced, and the slices baked again, forming a hard biscuit which allowed these early brewers to store some of their beer ingredients.
In a basket over a pitch lined urn, the loaves were crumbled up and water poured over the bread. When the urn was full a plug of clay was placed over the opening and the beer left to ferment. So, what was there to do the fermenting? These prehistoric brewers also added "the sweet thing" which is taken to be dates. There would have been wild yeast on the skins of the dates, and likely some wild yeast would have settled on the bread that was being crumbled and sparged with water, and probably yeast left in the fermenter from the last batch.
What of other continents? In the Americas there was no barley or similar grain, just maize. In good years the corn kernels would be used to make beer, in bad years the whole corn plant, every part of which is loaded with sugar, would be chopped up fine, mixed with water and left to ferment. In Asia and parts of Africa there are starchy tubers and millet that can be used. There are no enzymes in unmalted corn kernels or tubers to convert unfermentable starch into fermentable sugars. There are enzymes in human spit, and the women of the village would gather round and masticate corn or tapioca etc and spit this into a communal fermenter
The enzymes in the saliva converted starch into sugar and the wort was left to get on with fermenting, with you can be sure many supplications to the gods and rituals to prevent evil spirits turning the beer sour.
The bread beer and chicha, the Amarican Indian corn beer and the other primitive beers, are being made today. However mean, brutish and miserable your life may be it is always better if beer is available.
These early beers were often drunk while still fermenting, they had no other way to add any fizz to beer, and no way to prevent spoilage, remember!
"Secret Life of Beer" Storey Pubns
Clive LaPensee "Housebrewers Companion" CAMRA