Ten to twelve thousand years
ago, at approximately the same time that agriculture emerged, a parallel
specialization appeared: pastoralism, the herding of domesticated
or partially domesticated animals.
Pastoralism has much more in common culturally with hunting and gathering ways of life since it is necessity to move the herds continually in search of fresh pastures making this a wandering, nomadic way of life. For Pastoralists, human and livestock populations tended to fluxuate according to shifts in climatic conditions impacting the availability of grasses. While pastoral life is demanding and often dangerous, it is, as a way of life, relatively stable over long periods of time--like hunting and gathering is. What one generation knew and did, the next generation knew and did.
Pastoralism tended to develop
on marginal land apart from areas suitable for agriculture, often in semi-arid
regions. Frequently, the two ways of life, pastoralism and agriculture,
were compatible, or even mutually dependent upon one another through symbiotic
trade relationships. Wherever the two modes of life existed near one another,
a lively trade usually sprang up between farmers who had food and other
objects to exchange, and pastoral nomads, who had products such as hides,
wool, meat, and/or milk.
With their need for widespread
mobility, pastoral nomads frequently found settled agricultural groups.
Raiding was an alternative to trade -- one which was tempting and often
profitable. With their constantly increasing populations, agriculturalists
tended to encroach on the land that could be converted agricultural purposes.
This could adversely impact pastoralists who also needed that land for grazing.
In other words, with these two specializations, warfare emerged and became,
in some cases, common.