Posted on 04/25/2008 11:04:35 AM PDT by CarrotAndStick
WASHINGTON: Human beings for 100,000 years lived in tiny, separate groups, facing harsh conditions that brought them to the brink of extinction, before they reunited and populated the world, genetic researchers in a study said on Thursday.
"Who would have thought that as recently as 70,000 years ago, extremes of climate had reduced our population to such small numbers that we were on the very edge of extinction," said paleontologist Meave Leakey, of Stony Brook University, New York.
The genetic study examined for the first time the evolution of our species from its origins with "mitochondrial Eve," a female hominid who lived some 200,000 years ago, to the point of near extinction 70,000 years ago, when the human population dwindled to as little as 2,000.
After this dismal period, the human race expanded quickly all over the African continent and emigrated beyond its shores until it populated all the corners of the Earth.
The expansion marked the end of the Stone Age in Africa and the beginning of a cultural advancement that has led several archaeologists to consider it the start of modern man, with the advent of language and complex and abstract thought.
The migrations out of Africa are estimated to have begun some 60,000 years ago. But little was known about the human trajectory between Eve and that period.
Published in the American Journal of Human Genetics , the study analyzed the maternally-transmitted mitochondrial DNA of human populations in southern and eastern Africa who appear to have diverged from other groups 90,000 to 150,000 years ago.
The researchers said paleoclimatological data suggests that Eastern Africa went through a severe series of droughts between 135,000 and 90,000 years ago that may have contributed to population splits.
Tiny bands of early humans developed in isolation from each other for as much as half of our entire history as a species, explained the study's chief authors Doron Behar, a genographic associate researcher based at Rambam Medical Center, Haifa, Israel, and Saharon Rosset, of IBM T.J. Watson Research Center, New York and Tel Aviv University.
"It was only around 40,000 years ago that they became part of a single pan-African population, reunited after as much as 100,000 years apart," said Behar.
"This new study ... illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' history," said Spencer Wells, of the National Geographic Society.
"Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA," he added.
From a band of about 2,000 individuals, human beings have grown to a current population of about 6.6 billion.
“Hope you got the book out of the 99 cent bin.”
Actually, I got the book on the recomendation of people here at FR. It was either Sunken Civ or blam. It is a very readable account, but at the same time goes into considerable detail as to the scientific method by which the “speculation and hypotheses” were tested. A good read if one has any desire to better understand the scientific method. Those who prefer belief to knowledge will, of course, not be interested.
“Comets entering our atmosphere become extremely hot.”
This is true, but if they are big enough, they can make it down to the ground, and if they hit an ice sheet send large chunks of ice flying far away. Regarding the dinosaurs, the Yucatan strike was probably caused by an asteroid or meteor the size of Washington, DC cubed. We get hit by comets, asteroids and meteors. Another source, which I also did not get from the 99 cent bin is “Comet” by Carl Sagan and Ann Druyan, the 1997 rewrite.
You don’t realize the inanity of a theory supposing our semi-closed system receiving a white-hot huge comet that size and it not creating a warming, as opposed to a cooling effect? Of it not disrupting a precise orbit and rotation and seasons?
Sagan? I worship not at his feet. He came up with some interesting hypotheses. Parascientific conjecture, but not science.
And those who say it is are putting their faith in atheism.
Some are pleasant to discuss these topics with on occasion here at FR.
The problem comes when the faith of extremist anti-God theofascists militate via the legal system.
Yes, the initial effect would have been huge grass and forest fires, followed by starvation, disruption of ocean currents, and apparently in this case the thousand year Younger Dryas cooling event. There also was apparently a near reversal of the earths magnetic field. There could have been some influence on orbit and rotation, but not enough to shift the axis of the earth’s rotation relative to the sun or the mildly eliptical orbit around the sun, which 11,000 years ago had the Northern Hemisphere furthest from the sun in winter, and closest to the sun in summer, rather than the reverse which is the case today to our good fortune.
Wow, whole lotta shakin’ goin’ on.
There’s a persistent idea that the atmosphere protects the surface of the Earth and us from all space debris. Generally, the larger the object, the closer to the surface it gets. Anything starting out bus-sized has about a 50/50 chance of having surviving parts of itself hit the surface, or (from time to time) anything or anyone who happens to be in the way. Anything which starts out, say, 100 yards across will strike the surface, either as a large part of its core, or (as it breaks up) smaller debris (or both).
Asteroids and comets are moving so fast in their formerly nice quiet undisturbed orbits that, when they intersect the path of the Earth, won’t be appreciably slowed down, and will penetrate the 50 miles (the statutory boundary between space and our atmosphere) to the surface in under two seconds. There will be frictional heating of the air, but a) not much air, and b) not much time is involved.
If I get ambitious, I’ll read the rest of the thread and bore everybody some more.
The Mystery Of Mammoth Tusks With Iron Fillings
Alaska Report News | 3-5-2008 | Ned Rozell
Posted on 03/08/2008 2:03:28 PM PST by blam
http://www.freerepublic.com/focus/f-news/1982619/posts
Are you making fun of my aunt? ;)
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