Indo-European languages

The Indo-European language family originally developed across northern India, most of Europe, and Greater Iran, with other native branches appearing in Armenia, parts of southern India and Sri Lanka, the Maldives, and even as far east as Myanmar. In earlier times, these languages were also spoken in Anatolia and northwestern China. Today, the family splits into several branches, eight of which survive: four with hundreds of millions of native speakers each—Indo-Iranian, Italic, Germanic, and Balto-Slavic—and four with fewer than fifteen million each—Hellenic, Albanoid, Armenian, and Celtic. Two major branches, Anatolian and Tocharian, are extinct, along with many other individual Indo-European languages.

The most widely spoken Indo-European languages by native speakers today include Spanish, Hindustani (Hindi and Urdu), English, Portuguese, Bengali, Punjabi, Russian, Marathi, German, French, and Persian. Many smaller languages within the family are endangered. Roughly 3.4 billion people—42% of the world’s population—speak an Indo-European language as their first language, far more than any other language family. According to Ethnologue, about 446 living Indo-European languages exist, with 313 belonging to the Indo-Iranian branch alone.

All these languages descend from a single prehistoric tongue, reconstructed as Proto-Indo-European, spoken sometime between the Neolithic and early Bronze Age (roughly 3300–1200 BC). Scholars debate its homeland, but the leading theory—the Kurgan hypothesis—places it on the Pontic-Caspian steppe (modern Ukraine and southern Russia), linked to the Yamnaya culture and related groups during the 4th and early 3rd millennia BC. By the time writing emerged, Indo-European had already split into many languages across Europe and large parts of Asia. In the modern era, European languages like English, French, Portuguese, Russian, Spanish, and Dutch spread through colonialism to Africa, the Americas, Oceania, and northern Asia.

The earliest written evidence of Indo-European comes from the Bronze Age: Mycenaean Greek and the Anatolian languages Hittite and Luwian. The oldest records are isolated Hittite words and names found in Akkadian texts from the Assyrian colony at Kültepe in eastern Anatolia, dating to the 20th century BC. No written records of Proto-Indo-European itself survive, but aspects of its speakers’ culture and religion can be inferred from later daughter cultures. The Indo-European family has the second-longest recorded history of any language family, after Egyptian and the Semitic languages (both Afroasiatic). Studying its internal relationships and reconstructing its ancestor was central to developing historical linguistics as a formal discipline in the 19th century.

Linguists today generally reject any genetic link between Indo-European and other language families, though a few disputed hypotheses propose such connections.

The history of Indo-European linguistics began in the 16th century, when European visitors to India noticed similarities among Indo-Aryan, Iranian, and European languages. In 1583, English Jesuit Thomas Stephens wrote a letter from Goa noting parallels between North Indian languages and Greek and Latin. Around 1585, Florentine merchant Filippo Sassetti observed word similarities between Sanskrit and Italian (e.g., *devaḥ*/*dio* for ‘God’, *sarpaḥ*/*serpe* for ‘serpent’, *sapta*/*sette* for ‘seven’). Neither led to further study. In 1647, Dutch scholar Marcus Zuerius van Boxhorn theorized that Asian and European languages came from a common ancestor he called Scythian, including Dutch, Albanian, Greek, Latin, Persian, German, and later Slavic, Celtic, and Baltic—but his ideas went unnoticed. Ottoman traveler Evliya Çelebi noted German-Persian word similarities in 1665–1666. Gaston Coeurdoux compared Sanskrit, Latin, and Greek conjugations in the late 1760s, suggesting a relationship. Mikhail Lomonosov also compared Slavic, Baltic, Iranian, Finnish, Chinese, and Khoekhoe, arguing that related languages like Latin, Greek, German, and Russian split from common ancestors long ago. The hypothesis gained traction in 1786 when Sir William Jones highlighted striking similarities among Latin, Greek, and Sanskrit, tentatively adding Gothic, Celtic, and Persian.