Thursday, April 24, 2008

354)Humans were nearly wiped out 70,000 years ago says Spencer Wells of the National Geographic Society's Genographic Project

"An institution dedicated to proceeding beyond known limits must be committed to independent thinking. In a university scholars engage both orthodox and unorthodox ideas, seeking truth and understanding wherever they may be found. "(Aga Khan IV, Speech, 1993, Aga Khan University, Karachi, Pakistan)

"The great Muslim philosopher al-Kindi wrote eleven hundred years ago, "No one is diminished by the truth, rather does the truth ennoble us all"(Aga Khan IV, 27th May 1994, Cambridge, Massachusets, U.S.A.)

"My profession is to be forever journeying, to travel about the Universe so that I may know all its conditions."(Ibn Sina, aka Avicenna, 11th century Muslim Philosopher, Physician and Scientist, author of the Canon of Medicine, circa 1037CE)

In November 2007 I blogged about taking part in a National Geographic Study in which analysis of my cheek cell DNA revealed my ancestry from 10-15 thousand years ago:

The lead investigator of the above study was Spencer Wells who, through the same genetic studies, has now shown that human beings may have had a brush with extinction barely 10,000 years before the great migration of our ancestors out of Africa:

Humans nearly wiped out 70,000 years ago, study says

Story Highlights:
1)Drought in Africa reduced population into small, isolated groups, study says
2)Separate study says number of humans may have fallen to 2,000
3)Analysis: Humans banded together again in Stone Age, increased in numbers
4)Migrations out of Africa appear to have begun about 60,000 years ago

WASHINGTON (AP) -- Human beings may have had a brush with extinction 70,000 years ago, an extensive genetic study suggests.

Geneticist Spencer Wells, here meeting an African village elder, says the study tells "truly an epic drama."

The human population at that time was reduced to small isolated groups in Africa, apparently because of drought, according to an analysis released Thursday.

The report notes that a separate study by researchers at Stanford University estimated the number of early humans may have shrunk as low as 2,000 before numbers began to expand again in the early Stone Age.

"This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' history," Spencer Wells, National Geographic Society explorer in residence, said in a statement.

"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."
Wells is director of the Genographic Project, launched in 2005 to study anthropology using genetics. The report was published in the American Journal of Human Genetics.
Previous studies using mitochondrial DNA -- which is passed down through mothers -- have traced modern humans to a single "mitochondrial Eve," who lived in Africa about 200,000 years ago.

The migrations of humans out of Africa to populate the rest of the world appear to have begun about 60,000 years ago, but little has been known about humans between Eve and that dispersal.

The new study looks at the mitochondrial DNA of the Khoi and San people in South Africa, who appear to have diverged from other people between 90,000 and 150,000 years ago.

The researchers led by Doron Behar of Rambam Medical Center in Haifa, Israel, and Saharon Rosset of IBM T.J. Watson Research Center in Yorktown Heights, New York, and Tel Aviv University concluded that humans separated into small populations before the Stone Age, when they came back together and began to increase in numbers and spread to other areas.

Eastern Africa experienced a series of severe droughts between 135,000 and 90,000 years ago, and researchers said this climatological shift may have contributed to the population changes, dividing into small, isolated groups that developed independently.

Paleontologist Meave Leakey, a Genographic adviser, said: "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?"

Today, more than 6.6 billion people inhabit the globe, according to the U.S. Census Bureau.

The research was funded by the National Geographic Society, IBM, the Waitt Family Foundation, the Seaver Family Foundation, Family Tree DNA and Arizona Research Labs.

Related article from the Economist magazine
Before the exodus
Apr 24th 2008From The Economist print edition

For two-thirds of its history, Homo sapiens lived exclusively in Africa. Only now are the details of that period becoming clear:

MITOCHONDRIAL DNA is a remarkable thing. Itself the remnant of a strange evolutionary event (the merger of an ancient bacterium with the cell ancestral to all plant and animal life), it also carries the imprint of more recent evolution. In many species, humans included, it passes only from mother to child. No paternal genes get mixed into it. That makes it easy to see when particular genetic mutations happened, and thus to construct a human family tree.

The branches of that tree are now well studied. Humans started in Africa, spread to Asia around 60,000 years ago, thence to Australia 50,000 years ago, Europe 35,000 years ago and America 15,000 years ago. What have not been so well examined, though, are the tree's African roots. The genetic diversity of Africans probably exceeds that of the rest of the world put together. But the way that diversity evolved is unclear.

A study carried out under the auspices of the Genographic Project, based in Washington, DC, and just published in the American Journal of Human Genetics, goes some way towards correcting this oversight. The study's researchers, led by Doron Behar of the Rambam Medical Centre in Haifa and Spencer Wells of America's National Geographic Society, have used the mitochondrial DNA of more than 600 living Africans to show how genetic diversity has developed in Africa. In doing so, they have shed light on how modern man spread around his home continent long before he took the first, tentative steps into a bigger, wider world.

By the drought divided

The team paid particular attention to samples taken from the Khoi and San people of southern Africa. These people, known colloquially as bushmen, traditionally make their livings by hunting and gathering. Indeed, their way of life is thought by many anthropologists to resemble quite closely that of pre-agricultural people throughout the world.

Comparing Khoi and San DNA with that of other Africans shows that the first big split in Homo sapiens happened shortly after the species emerged, 200,000 years ago. Most people now alive are on one side of that split. Most bushmen are on the other. The consortium's analysis of which DNA “matrilines” are found where suggests that for much of its history the species was divided into two isolated populations, one in eastern Africa and one in the south of the continent, that were defined by this split. However, few other matrilineal splits from the first 100,000 years of the species's history have survived to the present day.

This suggests the early human population was tiny (so the opportunities for new matrilines to evolve in the first place were limited) and reinforces the idea that Homo sapiens may have come close to extinction (eliminating some matrilines that did previously exist). Indeed, there may, at one point, have been as few as 2,000 people left to carry humanity forward.

This shrinkage coincides with a period of prolonged drought in eastern Africa, and was probably caused by it. The end of the drought, however, was followed by the appearance of many new matrilines that survive to the present day. The researchers estimate that by 60,000-70,000 years ago, the period when the exodus that populated the rest of the world happened, as many as 40 such groups were flourishing in Africa—though that migration involved only two of these groups.

The African matrilines, however, seem to have remained isolated from each other for tens of millennia after the exodus. It was not until 40,000 years ago that they began to re-establish conjugal relations, possibly as a result of the technological revolution of the Late Stone Age, which yielded new and more finely crafted tools. Only the bushmen seem to have missed out on this panmictic party. They were left alone until a few hundred years ago, when their homelands were invaded from the north by other Africans and from the south by Europeans. Panmixis thus came full circle. And that particular party was certainly not a happy one.

Easy Nash

The Qur'an itself repeatedly recommends Muslims to become better educated in order better to understand God's creation: Aga Khan IV(2007)
The Quran tells us that signs of Allah's Sovereignty are found in the contemplation of His Creation: Aga Khan IV(2007)
This notion of the capacity of the human intellect to understand and to admire the creation of Allah will bring you happiness in your everyday lives: Aga Khan IV(2007)
Islam, eminently logical, placing the greatest emphasis on knowledge, purports to understand God's creation: Aga Khan IV(2006)