Re: MUSLIMS IN THE AMERICAS BEFORE COLUMBUS
http://afp.google.com/article/ALeqM5gXL-5uNUZirR8IgC01VdP-p6-tIQ
Might be of little relevence to the topic. but interesting nevertheless.
Glaciers blocked New World colonizers for 20,000 years: study
1 day ago
CHICAGO (AFP) — The first human migration into the Americas was blocked by two massive glaciers which kept early settlers on the doorstep of the New World for about 20,000 years, a study published Wednesday has found.
The study, which used DNA analysis to trace genetic changes over generations and then compared it with the geological and archaeological record, is the latest to challenge the standard story of how the Americas were populated.
Instead of a steady migration out of Asia and across the Bering Strait by an initial group of a hundred or less big game hunters, this data shows a gradual and interrupted expansion by a much larger group of between 1,000 and 5,400 people in three distinct stages.
The early generations began to move out of Siberia into Beringia, which is now under the icy waters of the Bering Strait, about 40,000 years ago.
They settled into the dry grasslands, which was productive enough to support large mammals but not rich enough to support significant population growth, after their eastward progression was blocked by two massive glaciers which covered much of what is now Alaska and northern Canada.
“If you think about it, these people didn’t know they were going to a new world,” said study co-author Connie Mulligan, assistant director of the University of Florida Genetics Institute.
“They were moving out of Asia and finally reached a landmass that was exposed because of lower sea levels during the last glacial maximum, but two major glaciers blocked their progress into the New World. So they basically stayed put for about 20,000 years. It wasn’t paradise, but they survived.”
Two passages opened up as the ice sheets started to melt about 15,000 years ago and the initial settlers expanded rapidly into the more fertile lands in the Americas, the analysis showed.
Within about four of five thousand years the land bridge across the Bering Strait was swallowed by the ocean, blocking further expansion out of Asia.
“The idea that people were stuck in Beringia for a long time is obvious in retrospect, but it has never been promulgated,” said Henry Harpending an endowed chairman of anthropology at the University of Utah who was not involved with the research.
“But people were in that neighborhood before the last glacial maximum and didn’t get into North America until after it. It’s very plausible that a bunch of them were stuck there for thousands of years.”
The researchers were able to reach these conclusions by analyzing the DNA of geographically and linguistically diverse populations distributed throughout the Americas.
“This was the raw material, the original genetic source for all of the Americas,” said co-author Michael Miyamoto, associate chairman of zoology at the University of Florida.
They found two distinct population increases at around 40,000 years ago and 15,000 years ago which were separated by a long period of little to no growth.
The first was a gradual sevenfold population increase as the group expanded from Central Asia. The second was a rapid sixteenfold increase, supporting the theory of a gradual expansion out of Asia and a rapid expansion into the Americas.
They also found evidence of genetic changes which accumulated during the 20,000 year period when the population held steady while waiting for the ice to retreat.
“By looking at the kinds and frequencies of these mutations in modern populations, we can get an idea of when the mutations arose and how many people were around to carry them,” Miyamoto said.
The study was published in PLoS ONE, the journal of the Public Library of Science