Beringia
Not a bridge to cross, but a country to live in
See it on the timeline →Beringia was not a bridge. It was a landmass the size of a continent, standing above water for tens of thousands of years, and people lived in it — they did not hurry across it.
Why it was dry
During the ice ages so much water was locked in ice that the sea stood around 120 metres lower than today. The Bering Strait is under fifty metres deep. As the sea fell, the seabed emerged as a plain over a thousand kilometres wide from north to south.
The climate was dry, cold and almost snowless — too dry for glaciers to build. It was grassland with herbs and shrubs, what researchers call the mammoth steppe, and it fed mammoth, bison, horse and reindeer.
Timeline
- the sea is low enough for Beringia to stand dry
- people live on the plains, genetically isolated from Asia
- the last glacial maximum; ice bars the way south
- the Pacific coastal route becomes ice-free
- the inland corridor between the ice sheets opens
- people are documented far south in both Americas
- the sea rises; Beringia disappears
- 50 metres of water over what was a plain
The standstill
Genetics made it plain. Indigenous Americans share a few mitochondrial founding lineages, and they differ from their north-east Asian relatives by an interval requiring several thousand years of isolation. The model is called the Beringian standstill: a population held between the ice to the east and Siberia to the west, becoming something distinct while it waited.
How long is disputed — estimates run from two to fifteen thousand years — but that it happened is widely accepted.
Two ways out
The inland corridor between the Laurentide and Cordilleran ice sheets was long taken to be the route. Newer dating shows it was not passable until around 14,000 years ago, and that it took time to gather enough plants and animals to feed anyone walking through.
The Pacific coastal route became ice-free earlier. It is harder to investigate because the coastline of the time now lies underwater, but finds on islands off British Columbia and in Alaska support it. Probably both were used.
The misleading word
"Land bridge" makes a continent sound like a footbridge. Beringia was larger than Alaska, stood above water longer than has passed since the ice age ended, and was home to people for hundreds of generations. It is not a place you cross. It is a place you are from.
For children
With so much water locked in ice, the sea fell and a dry plain emerged between Siberia and Alaska. It was over a thousand kilometres wide. People lived there for thousands of years — it was not a bridge to hurry across but a place with grass, animals and homes.
Sources
- Tamm m.fl., «Beringian Standstill and Spread of Native American Founders», PLoS ONE 2 (2007)
- National Park Service: Bering Land Bridge National Preserve
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