In 1786, a British judge named William Jones noticed striking similarities between certain words in languages, such as Sanskrit and Latin, whose speakers were separated by thousands of miles. The languages must have “sprung from some common source,” he wrote.

Later generations of linguists determined that Sanskrit and Latin belong to a huge family of so-called Indo-European languages. So do English, Hindi and Spanish, along with hundreds of less common languages. Today, about half the world speaks an Indo-European language.

Linguists and archaeologists have long argued about which group of ancient people spoke the original Indo-European language. A new study in the journal Nature throws a new theory into the fray. Analyzing a wealth of DNA collected from fossilized human bones, the researchers found that the first Indo-European speakers were a loose confederation of hunter-gatherers who lived in southern Russia about 6,000 years ago.

“We’ve been on the hunt for this for many years,” said David Reich, a geneticist at Harvard who led part of the new research.

Independent linguists had mixed reactions to the findings, with some praising their rigor and others highly skeptical.

Many decades ago, linguists began trying to reconstruct the proto-Indo-European language by looking at words shared by many different languages. That early vocabulary contained a lot of words about things like wheels and wagons, and few about farming. It looked like the kind of language that would have been spoken by nomadic herders who lived across the steppes of Asia thousands of years ago.

But in 1987, Colin Renfrew, a British archaeologist, questioned whether nomads who were constantly on the move would have stayed in any one place long enough for their language to catch on. He found it more plausible that early farmers in Anatolia (a region in what is now Turkey) spread the language as they expanded, gradually converting more and more land to farm fields and eventually building towns and cities.

The archaeologist argued that an Anatolian origin also fit the archaeological evidence better. The oldest Indo-European writing, dating back 3,700 years, is in an extinct language called Hittite, which was spoken only in Anatolia.

In 2015, two teams of geneticists — one led by Dr. Reich — shook up this debate with some remarkable data from ancient DNA of Bronze Age Europeans. They found that about 4,500 years ago, central and northern Europeans suddenly gained DNA that linked them with nomads on the Russian steppe, a group known as the Yamnaya.

Dr. Reich and his colleagues suspected that the Yamnaya swept from Russia into Europe, and perhaps brought the Indo-European language with them.

In the new study, they analyzed a trove of ancient skeletons from across Ukraine and southern Russia. “It’s a sampling tour de force,” said Mait Metspalu, a population geneticist at the University of Tartu in Estonia who was not involved in the research.

Based on these data, the scientists argue that the Indo-European language started with the Yamnaya’s hunter-gatherer ancestors, known as the Caucasus-Lower Volga people, or CLV.

The CLV people lived about 7,000 years ago in a region stretching from the Volga River in the north to the Caucasus Mountains in the south. They most likely fished and hunted for much of their food.

Around 6,000 years ago, the study argues, the CLV people expanded out of their homeland. One wave moved west into what is now Ukraine and interbred with hunter-gatherers. Three hundred years later, a tiny population of these people — perhaps just a few hundred — formed a distinctive culture and became the first Yamnaya.

Another wave of CLV people headed south. They reached Anatolia, where they interbred with early farmers.

The CLV people who came to Anatolia, Dr. Reich argues, gave rise to early Indo-European languages like Hittite. (This would also fit with the early Indo-European writing found in Anatolia.) But it was their Yamnaya descendants who became nomads and carried the language across thousands of miles.

Some experts praised the work. “It’s a very intelligent scenario that’s difficult to criticize,” said Guus Kroonen, a linguist at Leiden University in the Netherlands who was not involved in the studies.

But Dr. Metspalu hesitated to jump from the new genetic data to firm conclusions about who first spoke Indo-European. “Genes don’t tell us anything about language, period,” he said.

And Paul Heggarty, a linguist at Pontifical Catholic University of Peru, said that the DNA analysis in the study was valuable, but he rejected the new hypothesis about the first Indo-European speakers originating in Russia as “smoke and mirrors.”

In 2023, Dr. Heggarty and his colleagues published a study arguing that the first Indo-Europeans were early farmers who lived over 8,000 years ago in the northern Fertile Crescent, in today’s Middle East.

Dr. Heggarty suggested that the CLV people actually belonged to a bigger network of hunter-gatherers that stretched from southern Russia into northern Iran. Some of them could have discovered farming in the northern Fertile Crescent, and then developed the Indo-European language, which would align with his findings.

These early farmers could have given rise to Hittite speakers thousands of years later in Anatolia, he said, and later given rise to the Yamnaya. The Yamnaya brought Indo-European languages to northern and Central Europe, Dr. Heggarty argued, but they were only one part of a bigger, older expansion.

As the Indo-European debate advances, one thing is clear: Our understanding of its history now stands in stark contrast to the racist myths that once surrounded it. Nineteenth-century linguists called the original speakers of Indo-European Aryans, and some writers later pushed the notion that ancient Aryans were a superior race. The Nazis embraced the Aryan myths, using them to justify genocide.

But Dr. Reich said that studies on ancient DNA show just how bankrupt these Aryan stories were.

“There’s all sorts of mixtures and movements from places that these myths never imagined,” he said. “And it really teaches us that there’s really no such thing as purity.”