New Bacteria Study Tracks Early Human Migration From Siberia Into the Americas

Gut bugs and bacterias have provided new insights about the peopling of Siberia and human migration into the Americas, which may appear to be an unexpected source of information.

Helicobacter pylori is a bacteria that can cause stomach ulcers and dwells in people's digestive tracts. For at least the past 100,000 years, it has evolved alongside (and within) humans, accompanying people out of Africa, on cross-continental migrations, and beyond.

By reconstructing H. pylori's evolutionary path as it traveled about in the stomachs of early humans, an international team had provided more detail to the fragmentary fossil record of how and when people travelled from Siberia to the Americas.

(Photo: Oleg Nikishin/Getty Images)
401812 03: Men fish while sitting on the ice of the river Ob March 3, 2002, in Novosibirsk, East Siberia, Russia.

"This study now uses the powerful approach of ABC statistics to reconstruct and date the migrations of Siberian H. pylori (and their human hosts) across Siberia and to the Americas," researchers said per Phys.org.

But, more importantly, the study provides insight into the complicated history of Siberian people, some of whom seemed to have survived the worst of the last ice age.

"The peopling of Siberia and the Americas is intriguing for archaeologists, linguists, and human geneticists, but despite significant recent developments, many details remain controversial," the research team, led by zoologist Yoshan Moodley, wrote in a report from Proceedings of the National Academy of Sciences (PNas).

Everything from the time of human migration from Eurasia to the Americas to the routes taken by the first migrants has been challenged by fresh evidence in recent years.

Did humans cross land bridges or travel over kelp motorways along the coast? Did they arrive in the Americas as the trans-Siberian glaciers thawed, or were they there much earlier?

However, there are still some unanswered problems, primarily because ancient human remains are scarce and difficult to come by. Genetic studies that track slow steps in human evolution can only tell us so much.

Recent genomic analyses of ancient human DNA have provided more evidence that Siberia served as a crossroads for human migrations into northern America and western Eurasia.

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Bacteria in Human Gut Could Suggest More Historical Insights

As it turns out, the DNA sequences of bacteria living inside humans for a long period include more historical insights.

To better comprehend previous human migration, the researchers collected over 550 different strains of H. pylori from 16 ethnic and traditional language groups living in modern-day Siberia and Mongolia.

H. pylori infect more than half of the world's population, but little is known about the gut bug's presence or diversity in these distant areas.

The team wrote that the region's multiplicity of language groups suggests a complicated history of movement and isolation.

They went on to say that the patterns of human variety between different ethnic groupings are equally understudied.

H. pylori, as a bacterium, reproduce quickly in the human gut, mutating ever so little. As a result, comparisons of divergent strains can reveal how various groups of people worldwide are linked, making it a helpful marker of human migrations.

Florida Times News said Moodley and his colleagues recreated the evolutionary histories of H. pylori strains collected in Siberia and the Americas. They then calculated how individuals and H. pylori strains would have crossed the continental divide.

The researchers found that because humans across "the entire extent" of Siberia shared H. pylori strains with humans in North America, there was likely a single migration event as recently as 12,000 years ago.

However, growing archaeological data, ancient bones, and genetic studies all point to a considerably earlier human migration into the Americas, perhaps between 13,000 and 23,000 years ago.

How Ice Age Contributed To History

Another topic of contention is whether people who initially arrived in Siberia around 45,000 years ago stayed during the coldest portion of the previous ice age (about 20,000 years ago) or migrated south.

Ice sheets covered a quarter of the Earth's surface area and a third of Alaska during the last glacial maximum. Sea levels have also risen, exposing land bridges such as the one that originally connected Russia and Alaska over the Bering Sea.

The researchers concluded that some individuals must have survived in northern Siberia during the last ice age because researchers identified the same ancient H. pylori strains across the country.

Across the region, however, the team discovered a few more recently admixed H. pylori genotypes. This shows that once the weather warmed throughout the Holocene, around 12,000 years ago, isolated people in central and southern Siberia re-joined the hardy tribes in the north.

The study entitled "Helicobacter pylori's historical journey through Siberia and the Americas" is published this week (14 June) in the journal PNAS.