At the end of the last ice age, humanity entered a epoch of increasing technological sophistication. For reasons that are still debated, many of the large mammals hunted by humans became extinct, driving the development of new food sources: breadmaking considerably predates this period, but people in Mesopotamia now began cultivating wild cereal and pulses. Dogs had been domesticated over thousands of years; nomadic shepherding became possible through domestication of goats, sheep, horses, camels and, above all, cows.
In the Neolithic period farm animals were first domesticated and agriculture was introduced: it began in the Near East by the 8th millennium BC and spread to northern Europe by the 4th millennium BC. Neolithic societies in NW Europe left such monuments as causewayed camps, henges, long barrows, and chambered tombs
By 5000 BCE, livestock herding was sufficiently established to allow a widespread abandonment of hunter-gathering in favor of settled lifestyles. Pottery was increasingly useful, and permanent buildings, constructed from mudbrick, appeared. These technologies spread out of the Middle East through the Old World (the Americas developed agriculture independently, with only the llama available for domestication). With the arrival of bronze, stone was used less for tools and more for buildings.
The majority of the peoples of Europe and a substantial portion of the present and ancient peoples of western Asia speak closely related languages that all belong to the Indo-European language family. European colonial expansions and the spread of Euro-American culture have been so successful that nearly half the population of the planet now speaks an Indo-European language. Yet the place where this language family originated and the course of its earliest migrations have been topics of heated and inconclusive debate for more than two centuries.
The problem of Indo-European origins and migrations has been a major challenge to prehistorians, and the failure to develop a single fully convincing model is a salutary caution to anyone interested in tracing the path of migrations in the archaeological record. If increased doubt is the result of the type of intense discussion that tracing the roots of the Indo-Europeans has occasioned, then this does not bode well for many other hypothesized migrations that have seen far less scrutiny.