darcity
JF-Expert Member
- Jul 20, 2009
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Utafiti ulifanywa na timu tatu tofauti za watafiti umetoa jumuisho kuwa binadamu wa sasa waliopo ulimwenguni asili yao ni Afrika.
Utafiti uliohusisha mchanganuo wa kijenetiki wa watu 787 toka asili mbalimbali ulimwenguni ulithibitsha kwamba watu wasio Waafrika wa leo wanapata asili yao toka katika kundi moja lililohama Afrika kati ya miaka elfu 50,000 mpaka 80,000 iliyopita
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Modern humans evolved in Africa roughly 200,000 years ago. But how did our species go on to populate the rest of the globe?
The question, one of the biggest in studies of human evolution, has intrigued scientists for decades. In a series of extraordinary genetic analyses published on Wednesday, researchers believe they have found an answer.
In the journal Nature, three separate teams of geneticists survey DNA collected from cultures around the globe, many for the first time, and conclude that all non-Africans today trace their ancestry to a single population emerging from Africa between 50,000 and 80,000 years ago.
“I think all three studies are basically saying the same thing,” said Joshua M. Akey of the University of Washington, who wrote a commentary accompanying the new work. “We know there were multiple dispersals out of Africa, but we can trace our ancestry back to a single one.”
The three teams sequenced the genomes of 787 people, obtaining highly detailed scans of each. The genomes were drawn from people in hundreds of indigenous populations: Basques, African pygmies, Mayans, Bedouins, Sherpas and Cree Indians, to name just a few.
The DNA of indigenous populations is essential to understanding human history, many geneticists believe. Yet until now scientists have sequenced entire genomes from very few people outside population centers like Europe and China.
The new data already are altering scientific understanding of what human DNA looks like, experts said, adding rich variations to our map of the genome.
Each team of researchers tackled different questions about our origins, such as how people spread across Africa and how others populated Australia. But all aimed to settle the controversial question of human expansion from Africa.
In the 1980s, a group of paleoanthropologists and geneticists began championing a hypothesis that modern humans emerged only once from Africa, roughly 50,000 years ago. Skeletons and tools discovered at archaeological sites clearly indicated that modern humans lived after that time in Europe, Asia and Australia.
Early studies of bits of DNA also supported this idea. All non-Africans are closely related to one another, geneticists found, and they all branch from a family tree rooted in Africa.
Yet there are also clues that at least some modern humans may have departed Africa well before 50,000 years ago, perhaps part of an earlier wave of migration.
In Israel, for example, researchers found a few distinctively modern human skeletons that are between 120,000 and 90,000 years old. In Saudi Arabia and India, sophisticated tools date back as far as 100,000 years.
Last October, Chinese scientists reported finding teeth belonging to Homo sapiens that are at least 80,000 years old and perhaps as old as 120,000 years.
In 2011, Eske Willerslev, a renowned geneticist at the University of Copenhagen, and his colleagues came across some puzzling clues to the expansion out of Africa by sequencing the genome of an Aboriginal Australian for the first time.
Source: New York
Utafiti uliohusisha mchanganuo wa kijenetiki wa watu 787 toka asili mbalimbali ulimwenguni ulithibitsha kwamba watu wasio Waafrika wa leo wanapata asili yao toka katika kundi moja lililohama Afrika kati ya miaka elfu 50,000 mpaka 80,000 iliyopita
===========================
Modern humans evolved in Africa roughly 200,000 years ago. But how did our species go on to populate the rest of the globe?
The question, one of the biggest in studies of human evolution, has intrigued scientists for decades. In a series of extraordinary genetic analyses published on Wednesday, researchers believe they have found an answer.
In the journal Nature, three separate teams of geneticists survey DNA collected from cultures around the globe, many for the first time, and conclude that all non-Africans today trace their ancestry to a single population emerging from Africa between 50,000 and 80,000 years ago.
“I think all three studies are basically saying the same thing,” said Joshua M. Akey of the University of Washington, who wrote a commentary accompanying the new work. “We know there were multiple dispersals out of Africa, but we can trace our ancestry back to a single one.”
The three teams sequenced the genomes of 787 people, obtaining highly detailed scans of each. The genomes were drawn from people in hundreds of indigenous populations: Basques, African pygmies, Mayans, Bedouins, Sherpas and Cree Indians, to name just a few.
The DNA of indigenous populations is essential to understanding human history, many geneticists believe. Yet until now scientists have sequenced entire genomes from very few people outside population centers like Europe and China.
The new data already are altering scientific understanding of what human DNA looks like, experts said, adding rich variations to our map of the genome.
Each team of researchers tackled different questions about our origins, such as how people spread across Africa and how others populated Australia. But all aimed to settle the controversial question of human expansion from Africa.
In the 1980s, a group of paleoanthropologists and geneticists began championing a hypothesis that modern humans emerged only once from Africa, roughly 50,000 years ago. Skeletons and tools discovered at archaeological sites clearly indicated that modern humans lived after that time in Europe, Asia and Australia.
Early studies of bits of DNA also supported this idea. All non-Africans are closely related to one another, geneticists found, and they all branch from a family tree rooted in Africa.
Yet there are also clues that at least some modern humans may have departed Africa well before 50,000 years ago, perhaps part of an earlier wave of migration.
In Israel, for example, researchers found a few distinctively modern human skeletons that are between 120,000 and 90,000 years old. In Saudi Arabia and India, sophisticated tools date back as far as 100,000 years.
Last October, Chinese scientists reported finding teeth belonging to Homo sapiens that are at least 80,000 years old and perhaps as old as 120,000 years.
In 2011, Eske Willerslev, a renowned geneticist at the University of Copenhagen, and his colleagues came across some puzzling clues to the expansion out of Africa by sequencing the genome of an Aboriginal Australian for the first time.
Source: New York
