Kets are a living linguistic fossil.

Several hundred strong and dwindling, they inhabit swampy, mosquito-infested areas along the Yenisei, a mighty central Siberian river whose bright-blue waters flow into the Arctic Ocean.

Thousands of years ago, reindeer pastoralists and horse herders pressed Kets to flee their motherland between Mongolia and Lake Baikal northwards to the world's largest forest, the Siberian taiga.

Kets are the last remnants of the Paleo-Asian hunters and gatherers who once populated Southern Siberia and spoke a group of related tongues now called Yeniseic. Their tantalisingly difficult grammar, unusual verb system, and Chinese-like tones were unlike any other language spoken in the region.

The extinction and assimilation of Yeniseic-speakers accelerated after the czarist takeover that roughly coincided with the European conquest of the Americas - and also brought along infectious diseases, alcoholism, and conversion to Orthodox Christianity.

Stalinist-era collectivisation forced Kets to settle down in several villages, and their children were sent to boarding schools, where they forgot their parents' language.

As a result, Ket is now "severely endangered, with perhaps only a few dozen fully fluent speakers left - and these are mostly over 60 years old", Edward Vajda, a historical linguist at Western Washington University, told Al Jazeera.

The rest of the Yeniseic family died out - there's only one speaker of the Yugh tongue left alive. Nearly half of almost 7,000 languages spoken on Earth will disappear by the end of this century - one of them does every two weeks, along with its speakers' unique culture, mythology, and ways of life.

So what makes Ket even more unique?

Despite its isolation, obscurity, and a lack of alphabet until the 1980s, Ket is the only living evidence of what happened in the Americas - and happened more than once - even though Ket villages lie more than 4,000km away from Alaska, the springboard of human settlement of the New World.

The mainstream opinion of historians and linguists is that ancient Siberians crossed the now-submerged land bridge between Asia and Alaska more than 15,000 years ago - too long ago to identify links between hundreds of Native American languages and any Siberian tongue.

If it wasn't for Ket.

Three instead of one

In research published since 2008, Vajda has analysed Ket word forms and verbal systems, linking them to the Na-Dene language family, North America's largest. Tlingit, Navajo, and Apache nations are among the Na-Dene speakers scattered from Alaska to Arizona.

If Vajda's theory is right, it "will be major news in historical linguistics and in science in general", linguist John Kari of the University of Alaska Fairbanks said , addressing a 2008 conference on Na-Dene and Yeniseic languages that scrutinised and accepted Vajda's findings.

They add proof to a ground-breaking theory about how the Americas were settled.

Instead of just one migration, there were three waves of migrants, according to a 2012 analysis of whole genomes taken from 52 Native American and 17 Siberian groups.

"Native Americans descend from at least three streams of Asian gene flow. Most descend entirely from a single ancestral population that we call 'First American'," the researchers, led by David Reich of the Genetics Department of the Harvard Medical School, wrote.

"However, speakers of Eskimo-Aleut languages from the Arctic inherit almost half their ancestry from a second stream of Asian gene flow, and the Na-Dene-speaking Chipewyan from Canada inherit roughly one-tenth of their ancestry from a third stream."

Elusive genes

The researchers said, however, they found no genetic links with the Kets population because the few DNA samples obtained may have been contaminated - and because Native North Americans often refuse to give their DNA. Most genetic evidence for their study came from South America.

Tatiana Tatarinova, a Russia-born biologist from the University of Southern California, faced a similar problem.

She and an international group of researchers tried to confirm Vajda's theory by analysing ancestry-informative markers, or gene forms that establish the geographic origins of one's ancestors. But their study of genetic data from 46 Kets and 42 people from neighbouring ethnicities found no direct link to Na-Dene speakers.

"Collection of DNA from American Indians is very complicated" because they feel that genetic research offends their beliefs, Tatarinova told Al Jazeera in mid-April at a Genome Russia conference in the Moscow suburb of Skolkovo.

Her study established, however, that Kets are related to an ancient group that definitely crossed America - becoming the first humans in Greenland.

Kets are the lost cousins of "Inuk", a dark-haired, brown-skinned man who lived 4,000 years ago in western Greenland and whose genome was extracted from four permafrost-preserved hair and bone fragments in 2008. Inuk belonged to the so-called Saqqaq culture that disappeared around 800 BC - leaving no links to the later Inuit.

Mythical evidence

Siberian tiger population makes recovery

An unexpected analysis reveals a link that supports Vajda's theory.

Russian expert in comparative mythology Yuri Berezkin identified six "motifs" shared by Na-Dene speakers and the folklore of Southern Siberia, the Ket motherland.

"I don't mean a coincidence of separate motifs - such coincidences could be found between almost any pairs of folklore traditions," Berezkin, who works at the Museum of Anthropology and Ethnography in St Petersburg, wrote in a 2015 article.

"We're talking about a set of elements specific to Na-Dene and a certain region within the Old World."

These motifs include specific myths such as the tale about the first humans who live lazily consuming tasty, satiating fat or bone marrow and plants until a supernatural creature makes them inedible so that humans have to learn hunting or farming in order to survive.

Another shared motif is the story of an insect that feeds on human blood but lies about its origin to bigger and more dangerous animals (or a personification of thunder) so that they don't eat humans - or kill fewer people during storms.

Kets' kin in China and Caucasus?

One of the most daring theories that involves Ket is a hypothesis developed by Sergei Starostin, a titan of historical linguistics who died in 2005. The Russian scholar authored widely respected reconstructions of phonetic systems of ancient Chinese and Japanese, and pioneered computer analysis of hundreds of languages.

In his attempts to recreate human kind's linguistic past of tens of thousands of years ago, he claimed to have found proof of the Yeniseic linguistic family's relation to the Sino-Tibetan languages that include modern Chinese, Tibetan and Burmese and are spoken by more than 1.2 billion people. The Sino-Caucasian linguistic group, he proposed, also included dozens of languages spoken in Russia's mostly Muslim region of North Caucasus.

The mind-boggling theory was, however, rejected by many linguists and historians.

Sadly, the Ket language itself may soon cease to exist.

"Today, the language is taught in the first three grades of the local schools, but it is losing ground to Russian in everyday life," Vajda wrote .

"There is increased intermarriage with Russians, and the survival of the unique Ket language as a medium of everyday communication beyond the next two generations is in doubt."