Almost half of all people in the world today speak an Indo-European language, one whose origins go back thousands of years to a single mother tongue. Languages as different as English, Russian, Hindustani, Latin, and Sanskrit can all be traced back to this ancestral language.

Over the last couple of hundred years, linguists have figured out a lot about that first Indo-European language, including many of the words it used and some of the grammatical rules that governed it. Along the way, they’ve come up with theories about who its original speakers were, where and how they lived, and how their language spread so widely.

Most linguists think that those speakers were nomadic herders who lived on the steppes of Ukraine and western Russia about 6,000 years ago. Yet a minority put the origin 2,000 to 3,000 years before that, with a community of farmers in Anatolia, in the area of modern-day Turkey. Now a new analysis, using techniques borrowed from evolutionary biology, has come down in favor of the latter, albeit with an important later role for the steppes.

The computational technique used in the new analysis is hotly disputed among linguists. But its proponents say it promises to bring more quantitative rigor to the field, and could possibly push key dates further into the past, much as radiocarbon dating did in the field of archaeology.

“I think that linguistics might be in for a sort of equivalent of the radiocarbon revolution,” says Paul Heggarty, a historical linguist at the Pontificia Universidad Católica del Perú in Lima, and a coauthor of the new study; he described the computational approach in the 2021 Annual Review of Linguistics.

Revealing dead languages

To understand what’s going on, it helps to look at how the study of Indo-European languages developed.

During the 16th century, as travel and trade put Europeans in touch with more foreign languages, scholars became increasingly interested in how languages related to one another, and where they might have originated.

In the late 18th century, Sir William Jones, a British judge in India, noticed similarities in vocabulary and grammar in Sanskrit, Latin, and Greek that couldn’t have been coincidental.

Historical linguists have reconstructed much of the grammar and vocabulary of the ancestor to Indo-European languages, to the point where we can piece together what conversations might have sounded like. Turn on closed captions to see a translation of the reconstruction presented here.

For instance, the English word “father” is “pitar” in Sanskrit and is “pater” in Latin and Greek. “Brother” is “bhratar” in Sanskrit, “frater” in Latin. Although Jones wasn’t actually the first to notice the similarities, his pronouncement that there must be a common origin helped to spur on a movement to compare languages and trace their relationships.

A major advance came in 1882, when Jacob Grimm formulated what would later be called Grimm’s Law. Grimm is best known today as one half of the Brothers Grimm, who collected and published Grimm’s Fairy Tales. But in addition to being a folklorist, Jacob Grimm was also an important linguist.

Grimm showed that as languages developed, sounds changed in regular ways that could help make sense of how languages were related. For instance, the Indo-European word for “two” was “dwo.” But “dwo” was one of a number of words whose initial “d” changed to “t” as it passed into the common ancestor of English and German. Later, the “t” sound became “ts” in an ancestor to modern German. So the Indo-European word “dwo” became “two” in English and “zwei” (pronounced “tsvai”) in modern German. Other words starting with the “d” sound behaved similarly. Scholars discovered a lot of these sound shift patterns, each obeying different rules, as one language gave birth to another.

Together with these sound shifts, linguists also study how words are formed, such as the way that English adds an “s” to make a word plural. They also look at how words are arranged, such as the way that English puts subjects before verbs and verbs before objects. And, of course, they look at shared vocabulary. By comparing all these features of different languages, linguists are able to map how languages descended from one another, and to place them in family trees that show their relationships.

Grimm's Law: How speech sounds change as languages evolve

	French	English
p → f	pied	foot
t → th	trois	three
k → h	coeur	heart
d → t	dent	tooth (originally tanth)
g → k	grain	corn
bh → b	frêre (from *bhráter)	brother
Grimm’s Law describes the regularity of how sounds change in languages. The chart shows how some sounds from proto-Indo-European shifted in Germanic languages, such as English, while remaining the same in non-Germanic languages, such as French. (Adapted from L. Campbell / The History of Linguistics).

Today, linguists are in broad agreement on the basics of Indo-European language groupings and how they are related to one another. They agree that the original language, which they call Proto-Indo-European, split into 10 or 11 main branches, two of which are now extinct.

They also generally agree on where to put languages within the main branches. For instance, they know that the Italic branch gave us Latin, which itself developed into the Romance languages such as French, Spanish, and Italian. The Germanic branch developed into languages including German, Dutch, and English. And the Indo-Iranian branch resulted in languages like Hindi, Bengali, Persian, and Kurdish.