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During the coldest periods
of the final phase of the Ice Age, the Bering Strait, which nowadays
marks the boundary between Asia and America, was a large area
of land commonly known as Beringia which joined the two continents
together. This land bridge appeared when the giant glaciers were
at their greatest extent, retaining millions of litres of water
in the form of ice. This loss of water caused the sea level to
fall by more than ninety metres, leaving exposed a plain which
easily covered the ninety kilometres that today separate Siberia
from Alaska. This plain stretching over an area of approximately
1,400 square kilometres was, in fact, perhaps the widest "bridge"
ever known, and crossing it did not represent any risk at all.
A great variety of food was on offer in Beringia for the bands
of hunters who roamed there. Near the coast there were seals,
walruses, sea lions, fish and molluscs, not to mention various
species of sea bird, whose eggs were an excellent source of
nourishment. Inland, food supplies consisted mainly of caribou,
bison, horse and woolly mammoth, although it was possible to
get some variety by alternating these with certain roots, plants
and berries. When water levels rose, all possible traces and
remains of this journey were left beneath what is today the
Bering Sea, or are still awaiting discovery in some remote spot
on the coasts of Alaska or Siberia.
The Quaternary Period was one of great climatic change all
over the world. Large icecaps called glaciers formed several
times on our planet, freezing enormous volumes of water in the
oceans and causing sea levels to fall, and this in turn led
to large areas of land being exposed which are nowadays covered
by sea. But it was not only the coastlines that moved: the slow
advance of the cold and ice caused forests and grasslands to
change place as well, and the areas where the large mammals
used to live got considerably smaller. At times of greatest
shortage, many animals left Siberia via southern Beringia, where
there was no ice, and entered Alaska, or vice versa.
The 'bridge' was open and closed many times during the different
glaciations of the Quaternary Period. 70,000 years ago, for
example, animal species from the Asian tundra and steppe were
able to enter North America. And during the last of these open
periods, up to 9,000 years ago, human beings had their last
opportunity to cross over.
Between one glaciation and the next were so-called "inter-glacial"
periods, when the climate was milder and the ice retreated.
There were variations even within each glaciation, and the climate
gradually became less harsh. These worldwide climate changes
also affected tropical zones far from the poles, although the
consequences were different. In areas near the equator and in
the high Andes, the climate got colder and drier at times when
the glaciers were advancing, but there was no ice, and as forests
shrank they were replaced by open stubble and pasture. East
of the Andes, where the Amazon jungle is today, a continuous
plain formed during cold periods, but the jungle returned when
the glaciers retreated once more.
It's a chilling thought, trying to imagine this final phase
of the Ice Age in our Andean range! Giant armadillos and sloths
must have been common sights on its high plains and in its wide
valleys, along with groups of horses, bears, wild pigs, deer
and mastodons. But humans would be arriving soon.
Man's first
marks on the continent
America at
the end of the Ice Age
Stones tell
their own story
Colombia: Gateway
to South America
A splendid
dinner 8,000 years ago
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