Conversely, the modern Indo-European language still most similar to PIE is Lithuanian. Our first preserved Lithuanian texts, from around 1500 AD, contain as high a fraction of PIE word roots as did Sanskrit texts of nearly 3,000 years earlier. The conservatism of Lithuanian suggests that it has been subject to few disturbing influences from non-Indo-European languages and may have remained near the PIE homeland. Formerly, Lithuanian and other Baltic languages were more widely distributed in Russia, until Goths and Slavs pushed the Baits back to their current shrunken domain of Lithuania and Latvia. Thus, this reasoning too suggests a PIE homeland in Russia. A third clue comes from the reconstructed PIE vocabulary. We already saw how its inclusion of words for things familiar in 4000 BC, but not for things unknown until 2000 BC, helps date the time when PIE was spoken. Might it also pinpoint the place where PIE was spoken? PIE includes a word for snow (snoighwos), suggesting a temperate rather than tropical location and providing the root of our English word 'snow'. Of the many wild animals and plants with PIE names (like mus meaning mouse), most are widespread in the temperate zone of Eurasia and help to pin down the homeland's latitude but not its longitude.
To me, the strongest clue from the PIE vocabulary is what it lacked rather than included—words for many crops. PIE speakers surely did some farming, since they had words for plough and sickle, but only one word for an unspecified grain has survived. In contrast, the reconstructed proto-Bantu language of Africa, and the proto-Austronesian language of Southeast Asia, have many crop names. Proto-Austronesian was spoken even longer ago than PIE, so that modern Austronesian languages have had more time to lose those old names for crops than have the modern Indo-European languages. Despite that, the modern Austronesian languages still contain far more old names of crops. Hence PIE speakers probably actually had few crops, and their descendants borrowed or invented crop names as they moved to more agricultural areas. That conclusion presents us with a double puzzle. Firstly, by 3500 BC farming had become the dominant way of life in almost all of Europe and much of Asia. That severely narrows down the-possible choices for the PIE homeland; it must have been an unusual area where farming was not so dominant. Secondly, it begs the question why PIE speakers were able to expand. A major cause of the Bantu and Austronesian expansions was that the first speakers of those language families were farmers, spreading into areas occupied by hunter-gatherers whom they could outnumber or dominate. For PIE speakers to have been rudimentary farmers invading a farming Europe turns historical experience on its head. Thus, we cannot solve the 'where' of Indo-European origins until we have come to grips with the hardest question: why?
In Europe just before the age of writing, there were not one but two economic revolutions so far-reaching in impact that they could have caused a linguistic steamroller. The first was the arrival of farming and herding, which originated in the Near East around 8000 BC, leapt from Turkey to Greece around 6500 BC, and then spread north and west to reach Britain and Scandinavia. Farming and herding permitted a large increase in human population numbers over those previously sustainable by hunting and gathering alone (Chapter Ten). Colin Renfrew, Professor of Archaeology at the University of Cambridge in England, recently published a thought-provoking book arguing that those farmers from Turkey were the PIE speakers who brought Indo-European languages to Europe.
My first reaction to reading Renfrew's book was, 'Of course, he must be right! Farming had to produce a linguistic upheaval in Europe, just as it did in Africa and Southeast Asia. This is especially likely since, as geneticists have shown, those first farmers made the biggest contribution to the genes of modern Europeans.
But—Renfrew's theory ignores or dismisses all the linguistic evidence. Farmers reached Europe thousands of years before the estimated arrival of PIE. The first farmers lacked, and PIE speakers possessed, innovations like ploughs, wheels, and domesticated horses. PIE is strikingly deficient in words for the crops that defined the first farmers. Hittite, the oldest known Indo-European language of Turkey, is not the Indo-European language closest to pure PIE, as one might expect from Renfrew's Turkey-based theory, but is instead the most deviant language and the one least Indo-European in its vocabulary. Renfrew's theory rests on nothing more than a syllogism: farming probably caused a steamroller, the PIE steamroller requires a cause, so farming is assumed to have been that cause. Everything else suggests that farming instead brought to Europe the older languages that PIE overran, like Etruscan and Basque.
Yet around 5000–3000 BC—at the right time for PIE origins—there was a second economic revolution in Eurasia. This later revolution coincided with the beginnings of metallurgy and involved a greatly expanded use of domestic animals—not just for meat and hides, as humans had been using wild animals for a million years, but for new purposes that included milk, wool, pulling ploughs, pulling wheeled vehicles, and riding. The revolution is richly reflected in the PIE vocabulary, through words for 'yoke' and 'plough', 'milk' and 'butter', 'wool' and 'weave', and a host of words associated with wheeled vehicles ('wheel', 'axle', 'shaft', 'harness', 'hub', and 'lynch-pin'). The economic significance of this revolution was to increase human population and power far beyond the levels made possible by farming and herding alone. For instance, through milk and its products one cow gradually yielded many more calories than did its meat alone. Ploughing allowed a farmer to plant much more acreage than he could with a hoe or digging stick. Animal-drawn vehicles allowed people to exploit far more land and still bring its produce to their village for processing.
For some of these advances it is hard to say where they arose, because they spread so quickly. For example, wheeled vehicles are unknown before 3300 BC, but within a few centuries of that date they are widely recorded throughout Europe and the Middle East. But there is one crucial advance whose origin can be identified: the domestication of horses. Just before their domestication, wild horses were absent from the Mideast and southern Europe, rare in northern Europe, and abundant only in the steppes of Russia eastwards. The first evidence of horse domestication is for the Sredny Stog culture around 4000 BC, in the steppes just north of the Black Sea, where archaeologist David Anthony has identified wear-marks on horses' teeth that indicate use of a bit for riding.
Throughout the world, wherever and whenever domestic horses have been introduced, they have yielded enormous benefits for human societies (Chapter Fourteen). For the first time in human evolution, people could travel overland faster than their own legs could propel them. Speed helped hunters run down their prey and helped herders manage their sheep and cattle over large areas. Most importantly, speed helped warriors to launch quick surprise raids on distant enemies and to withdraw again before the enemies had time to organize a counterattack. Throughout the world the horse revolutionized warfare and enabled horse-owning peoples to terrorize their neighbours. The stereotype that Americans hold of Great Plains Indians as fearsome mounted warriors was actually created only recently, within a few generations from 1660 to 1770. Since European horses reached the US West in advance of Europeans themselves and other European goods, we can be sure that the horse alone was what transformed Plains Indian society.
The inferred homeland where proto-Indo-European (PIE), the mother tongue, was spoken lay in the Russian steppes north of the Black Sea and east of the Dnieper River.