Posted on 10/31/2012 1:10:13 AM PDT by LibWhacker
DNA sequencing of 36 complete Y chromosomes has uncovered a previously unknown population explosion that occurred 40 to 50 thousand years ago, between the first expansion of modern humans out of Africa 60 to 70 thousand years ago and the Neolithic expansions of people in several parts of the world starting 10 thousand years ago. This is the first time researchers have used the information from large-scale DNA sequencing to create an accurate family tree of the Y chromosome, from which the inferences about human population history could be made.
"We have always considered the expansion of humans out of Africa as being the largest population expansion of modern humans, but our research questions this theory," says Ms Wei Wei, first author from the Wellcome Trust Sanger Institute and the West China University of Medical Sciences. "The out-of-Africa expansion, which happened approximately 60,000 years ago, was extremely large in geographical terms with humans spreading around the globe. Now we've found a second wave of expansion that is much larger in terms of human population growth and occurred over a very short period, somewhere between 40,000 to 50,000 years ago."
There is no obvious archaeological event that would explain why this sudden expansion in the human population occurred. One possible theory is that during the original out-of-Africa expansion, humans moved along the coastlines of the world, settling as they went. Their origins and genetic makeup would mean that these people were suited to coastal life, but not to the demands of living inland. This would have prevented large population growth as the coasts could only sustain a certain number of people.
"We think this second, previously unknown population boom, may have occurred as humans adapted to their new environment after the first out-of-Africa expansion," says Dr Qasim Ayub, lead author from the Wellcome Trust Sanger institute. "We think that when humans moved from the horn of Africa to Asia, Australia and eventually Europe, they remained in small groups by the coasts. It took them tens of thousands of years to adapt to the mountainous, forested surroundings on the inner continents.
However, once their genetic makeup was suited to these new environments, the population increased extremely rapidly as the groups travelled inland and took advantage of the abundance of space and food." The work highlights how it is now possible to obtain new biological insights from existing DNA sequencing data sets, and the value of sharing data. The majority of the DNA information used for this study was obtained from freely-available online data-sets.
Since the Y chromosome is found only in men, its history and evolution are easy to study and interpret. This study also highlights how information generated by other genetic studies, in this case by the company Complete Genomics, can be used to investigate human genetic archaeology. The lengths between the branches and the length of each branch on the Y chromosome family tree provide insights into the evolution of the human population. The closer the branches are, the more rapidly the population was expanding and separating, most likely into different geographic areas. The longer the branch length, the greater the time that group of people have been separated from the other groups.
"We have provided a nearly ten-fold increase in the number of genetic markers found on Y chromosomes and discovered new historical insights into the evolution of modern humans using DNA sequencing information from just 36 men," says Dr Chris Tyler-Smith, lead author from the Wellcome Trust Sanger Institute. "We now want to look at ten times this number of Y chromosomes in data from the 1000 Genomes Project. Who knows what we will find then?"
Your point is wrong. Lactose tolerance is a new mutation. As just one of thousands of examples. Where do you think current genetic diversity comes from? There is far more useful variation than could be contained within just two individuals.
Look at the genetic diversity of dogs. One cannot derive that vast diversity just from mixing those genes within a wolf population!
New and useful variations arise all the time in bacteria, how would it therefore be impossible for it to do so in human populations?
Man has been drinking milk for as long as there has been man. We've always been lactose tolerant. Some people just more than others
Look at the genetic diversity of dogs. One cannot derive that vast diversity just from mixing those genes within a wolf population!
Excellent example of intelligent design. There are breeds of dogs because we selective bred those breeds out of the wild canine populations.
New and useful variations arise all the time in bacteria, how would it therefore be impossible for it to do so in human populations?
Man is not a bacteria.
And yet some claim that no creationist is ignorant enough to deny MICRO evolution. But you just did, outside of bacteria I guess. Thus we see the limits of primitive and superstitious thinking.
Believe what you choose to believe. I’ll believe what is true.
It is a denial of truth with no intelligence required. Humans cannot create genetic variation in dogs through intelligent design, but apparently you think it is some totem that explains everything while doing exactly nothing. Say “intelligent design” and it will make the problems go away. Nevermind that it is an explanation of evolution NOT a lame excuse for how evolution doesn’t happen. Truth? You can’t handle the truth!!! ;)
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