Beer versus dairy: complementarity farmers - pastoralists.
The Neolithic period implies the sedentarisation of only a part of the population: the farmers. The semi-nomadic pastoralists walk behind their herds and remain subject to the annual cycles of reproduction and grazing. What has been said of communities grouped together in villages around their starch stocks applies to the farmers. Their way of life (urbanisation, hierarchical society, food dependence on grain) called them to become brewers' peoples.
But this ecological and social specialisation does not imply that livestock breeders were expelled to the abandoned territories of the farmers or thrown back to the fringes of the cultivated-urbanised areas, in the night of history. These early pastoralists were not the nomads of the great steppes of Central Asia. They live in symbiosis with the farmers and, like them, frequent the urban world of the first cities. In most cases, depending on the ecosystems and human cultures in situ, herders and farmers led complementary, rather than autonomous or conflicting, lifestyles. To the first ones milk, cheese and meat, to the second beer, bread and porridge. Mesopotamian pastoralists and farmers constantly exchanged their products.
A very early Sumerian text (3th millennium BC) stages a banquet of the gods according to a standard topic of the Mesopotamian world:
« They drank sweet wine, they drank tasty beer, and when they had drunk sweet wine, and were filled with tasty beer, they began a quarrel in the middle of the flooded fields, they quarrelled in the Banqueting Hall. »
Dispute does not mean here a pitched battle, but a verbal jousting and contradictory debate on the true nature of things, the equilibrium of the world and the virtues of each person.
Cause of the Dispute : in ancient times, the Great Gods created two gods who teach men to cultivate plants and make herds growing in order to provide the Divine Banquet : Ashnan (litt. Grains) protectress of agriculture, and Lahar (litt. sheep) keeper of flocks. Indeed, what was there on earth before the cereals ?
« The people of those days,
did not know about eating bread.
They did not know about wearing clothes;
they went about with naked limbs in the Land.
Like sheep they ate grass with their mouths,
and drank water from the ditches.. » 
Who should have the pre-eminence, who should bend before the other: Ashnan the farmer or Lahar the shepherd? Each one defends his attributes before the divine assembly. Lahar claims wool, clothes, meat of the herds, pure milk, rare oils, skin and leather sandals, in short, the flagship products of the world of the semi-nomadic herders. Ashnan is proud of all cereal products, therefore beer. Here is one of her claims:
« When the BAPPIR has been carefully prepared in the oven,
and the TITAB tended in the oven,
Ninkasi [Mesoptamian goddess of beer] mixes them for me.
while your big billy-goats and rams
are despatched for my banquets.
On their thick legs they are made to stand separate from my produce.
Your shepherd on the high plain eyes my produce enviously.. » 
Here we are dealing with the brewing of beer. BAPPIR and TITAB are in the hands of Ninkasi, the Sumerian goddess of brewing, the ingredients of her craftsmanship. BAPPIR is a beer-bread composed of "raw grains + plants", certainly a bread made of cooked grains and amylolytic plants, lightly baked on the surface to be preserved. The TITAB is a beer-bread of same nature but made from malted grains. Ashnan thus claims, through her description of the fermented beverage served at the royal tables, the pride of place at their banquets! Beer, the grain beverage, must precede meat. Even the shepherd, from the depths of his steppe and his sheepfold, covets the pleasure and effects of beer.
The hinted images given by the Dispute express here the geopolitics of cereal growers with regard to pastoralists. Bread and beer, specialities of sedentary life, attract these wandering and bellicose groups, often ascetic by necessity. Emblems of the farming and urban cultures, bread and beer attract human flows to labour-hungry cities. Peacefully or brutally :
« When I come upon a captive youth and give him his destiny, he forgets his despondent heart and I release his fetters and shackles » utters Ashnan. Bread and beer relieve many pains !
But Ashnan adds : « When I am standing in stalks in the field, my farmer chases away your herdsman with his cudgel. »
Beyond the recurrent local conflicts raised by the courses and grazing of the herds of sheep and goats, one can guess some dialectic. If the overflowing silos of grains founded the political strength of the first city-states - bread and beer rations for soldiers and servile labour -, they ipso facto transformed these same cities and villages into prey for wandering bands from the farthest reaches of the steppes, deserts or mountains. Bands ready to plunder when the power of the cities weakens in the great plains. This balance induces, in times of peace, regular social exchanges between the world of farmer-irrigators and that of pastor-hunters. They take the form of "bread-beer" versus "meat-dairy" barter, based on sociability and exchanges between two complementary economic spheres. This is the deep political meaning of the Dispute of Ashnan and Lahar.
If Mesopotamian pastoralists and farmers contribute to the general prosperity, the policy of the city-states dictates that the breeders bend their knees before the cereal power of the cities. Ashnan is declared winner of the Dispute by the Great Gods of the Mesopotamian pantheon, Enki and Enlil. Other texts grant preeminence to the shepherds, notably in the cycle of the goddess Inanna and Dumuzi, guardian of the flocks.
This Dispute, exemplary for its antiquity and the explicit meaning of the text, has been replayed each time pastoralists and farmers have clashed in the past. Here are some historical cases:
- Occasional barter exchanges: grain/malt/beer for meat/fur/pellets. Examples :
- Case of the Mongols who know how to ferment mare's milk and produce an indigenous alcoholic drink (koumiss). However, they occasionally exchange with the farming and brewing peoples of the southern fringes of the Asian steppe. (Fermented beverages of central Asia peoples).
- Case of the Xiongnu pastoralists in northern China. Exchange of beer and malt with the court of the Great Empire of Han 202 BC-220 AD (China).
- Peul breeders from sub-Saharan regions in contact with farmers-brewers in the Niger Basin.
- Seasonal exchanges made permanent: grain for meat or horses. This economic complementarity enables semi-nomadic breeders to brew beer. Examples :
- Syria of the 2nd millennium: sheep breeders of the Djezire River <=> urban cultures of the Middle Euphrates.
- Southern border of Egypt during the Middle Kingdom and its relationship with Sudanese cultures.
- Nomads of the steppes of Central Asia (Kazakhstan) <=> farmers of the eastern and southern borders.
- Yak breeders from the Tibetan plateau <=> farmers-brewers from the Tibetan valleys (chang barley beer).
- Breeders of llamas from the Andean highlands <=> farmers of the low valleys (chicha corn beer).
- The balance of power: nomadic pastoralists become the predators of sedentary farmers-brewers when the latter's political and military power weakens or breaks down. Historical examples are numerous. Among the oldest, the peoples who came from the Zagros mountains or the Iranian highlands toppled the Mesopotamian dynasties (Sargon, Ur III). The peoples known as the Sea peoples swept over northern Egypt. In more recent times : Xiongnu (northern China), Huns (central Europe), Mongols (central Asia), Moghols (northern India), Aztecs (central Mexico), Fulani in the 18-19th centuries (Africa of the Niger basin).
 Alster, Vanstisphout 1987, 1-43. English translation http://etcsl.orinst.ox.ac.uk/cgi-bin/etcsl.cgi?text=t.5.3.2# §12-25