Were Europe and North America connected? Chinese team’s ‘land bridge’ theory challenges view of Native American ancestry
The land bridge theory suggests that Native Americans are genetically closer to Western Europeans than Asians
Chinese researchers studying fossilised leaves in southern Yunnan province claim to have discovered plant evidence that Europe and North America were connected by a land bridge until “fairly recently”.
The finding could help explain why Native Americans are genetically closer to Western Europeans than contemporary Asians, even though the general consensus among the scientific community is that Native Americans originally hailed from parts of Asia.
The team found a fossil of Mahonia, or barberry, a genus that includes about 70 species of evergreen shrubs, in the Chinese province that is believed to be the oldest of its kind in the country.
The research was led by Prof. Zhou Zhekun at the Chinese Academy of Sciences’ Kunming Institute of Botany. Kunming is the Yunnan provincial capital.
Yet at 5 million years of age, the latest discovery is still greatly pre-dated by similar fossils discovered in Europe, where the plant became extinct during the last great ice age.
As barberry originated in North America 50 million years ago, this suggests a pattern of plant migration moving southeast from what now stands as the United States across the Atlantic to Europe and then on to Asia, the team said.
The same route may have been used by humans many years later, but in the opposite direction.
“This fossil provides us with solid evidence that the barberry plants [found] in America came to Europe before they arrived in Asia,”said Professor Su Tao, who helped author the recent paper on the subject published in the Journal of Plant Research.
Wild barberry populations are now evenly distributed on both sides of the Pacific, in western parts of the United States and East Asia.
This helped give rise to the widely held belief that a prehistoric land bridge once existed between Asia and America. Dubbed the Bering, it connected Siberia and Alaska.
But the latest finding suggests a second land bridge may have existed, too.
“If Mahonia came to Asia via the Bering land bridge, our fossil should have been older than those found in Europe,” said Su.
His team speculated that Europe and North America were once connected by a vast strip of land that included Greenland. Once sea levels rose, this would have vanished from view.
Though the plant’s migration would have taken place several million years before early humans started shifting from one global destination to another, they may have shared a similar route, according to Su.
This challenges the popular view that Native American’s ancestors came from Asia via the Bering land bridge. The fact that the early Americans and Asians share similar facial and other features was used to support such claims.
But some studies in recent years have attempted to debunk that theory.
One paper published in Nature in 2013 claimed that Native Americans show little genetic relationship to Asians, particularly Chinese. Instead, it linked the indigenous people of North America to Western Europeans.
Yet even this paper could not explain how early human settlers crossed the Atlantic and reached America.
If such a land bridge between the two continents did once exist, there is no reason why humans wouldn’t have used it, according to Su, an associate researcher at the Kunming Institute of Botany.
Logically, human hunters follow animals who prey on smaller creatures and plants, these being at the bottom of the food chain.
Moreover, barberry’s migration route hints at the existence of a giant belt of evergreen forest stretching between all three continents, one that was nourished by sufficient rainfall and warm climes, the team said.
“The Bering land bridge lacked such forests. Instead, it was composed of mostly ice and snow,” Su said.
“If I was an early human, I would have preferred trekking through forests rather than over glaciers,” he added.