Posted on 01/06/2003 8:43:40 AM PST by blam
Tracing your tribe's wanderings through DNA
January 06 2003 at 06:20AM
Palo Alto, California - Scientists say they can tell where a person comes from just by looking at the genes. Researchers found that tiny differences in DNA can provide enough information to identify the geographic ancestry of individual people.
This could be used to shed light on the course of ancient human migrations across the globe. Scientists already know that every individual human being has DNA 99,9 per cent identical to everyone else despite differences in skin colour, body or skull shape.
But the study by United States scientists wanted to see if they could predict where an individual was from by taking DNA samples from from 1 056 people from 52 populations in five major regions; Africa, Eurasia (Europe, the Middle East, Central and South Asia), East Asia, Oceania and the Americas.
Professor Marcus Feldman of Stanford University, who led the international study, said: "We took the labels off of all the individuals so we didn't know where they came from. Then we asked the question: can we look at the DNA and detect where groups of individuals form clusters that are genetically related to one another?"
'We took the labels off of all the individuals' Researchers then applied a statistical technique that uses many independent genes to detect the geographic patterns of ancestry in samples. The research team, including scientists in the US, France and Russia, accurately pinpointed the ancestral continent of virtually every individual from Africa, East Asia, Oceania and the Americas.
People from Eurasia, which includes Europe, the Middle East and Central/South Asia, were among the most difficult to assign ancestries, Feldman noted. "A complex history of migrations, conquests and trade over the past few thousand years is likely to be the cause for this difficulty," he said.
An exception were the Basques of Spain - a geographically and linguistically isolated population that was genetically distinguishable from other European groups.
The study, Genetic Structures of Human Populations, published in Science magazine, also supports recent genetic studies of human migration, confirming migratory patterns between Europe and West Asia, Europe and Central America and other continents as well. - Sapa-DPA
09:20 06 January 03
Exclusive from New Scientist Print Edition
Hunting skills may not after all have triggered the tremendous burst of human evolution at the beginning of the ice ages nearly two million years ago. Instead of man the hunter, the driving force behind this evolutionary surge may have been woman the gatherer, with both mother and grandmother playing a vital role.
Hunter or scavenger
For 40 years, anthropologists have leaned toward the notion that rich, nourishing meat - brought home by hunters and shared out - played a crucial role in human origins. This would explain why evolution selected for larger, smarter hunters with lighter jaws and teeth: precisely the changes seen as Homo erectus arose in eastern Africa.
The hunter-driven scenario also included the formation of nuclear family groups, in which men hunted while women gathered plants and cared for their children, thus kicking off humans' social evolution as well.
But this picture may be wrong on several counts. To begin with, early men probably were not bringing meat home to the family. Most evidence of hunting by early African Homo erectus comes from archaeological sites containing both animal bones and primitive stone tools. But most of these lie next to rivers, the kind of predator-filled habitat that today's Hadza hunter-gatherers in Tanzania call a "city of lions".
"They're certainly not places where early humans were spending the night," says James O'Connell, an anthropologist at the University of Utah in Salt Lake City. O'Connell is lead author of a critique of the hunting hypothesis published in the latest issue of the Journal of Human Evolution (vol 43, p 831).
Fast food
Instead, the remains probably represent temporary meal sites - perhaps a convenient patch of shade - where the group gathered around a fallen animal, O'Connell and his team suggest.
Most likely, the "hunters" were not actually hunting either. Many of the bones bear both cut-marks from primitive stone tools and the tooth marks of animals. When the researchers compared these with marks on bones made in modern experiments, they found that the pattern of marks and the mix of bones were similar to those left by human scavengers (see graphic).
This suggests that early humans drove other predators away from freshly killed carcasses - a view now gaining support among palaeoanthropologists. But O'Connell's team went a step further. They wanted to know what kind of a living early African Homo erectus made if in fact they were scavengers, not hunters.
The Hadza people today scavenge avidly in the same way, and studies in the late 1980s noted that they found an average of one carcass every two to three weeks. Based on that observation, the team estimated that early humans might have picked up a carcass every few days in the wettest areas, but in drier areas might have got as little as one a month: nowhere near enough to live on.
If fathers were not feeding their children meat most of the time, that means mothers and, perhaps, grandmothers must have been. Older women might have proved crucial in feeding children, the researchers say, allowing the mothers to get pregnant again more quickly.
Evolution would thus favour a long lifespan, which is closely linked to large body size and delayed maturity. Suddenly, all the major changes in human life history are explained by foraging, not hunting.
Critics point out that even if the meat supply was not reliable enough to live on, it must have been important in evolutionary terms. Humans have been top carnivores - a highly unusual role for a primate - since at least the Stone Age.
"Something special did happen with regard to carnivory," says Robert Blumenschine, a palaeoanthropologist at Rutgers University in New Brunswick, New Jersey. "The extent to which it shaped human evolution remains in question, but I would think it must have had some strong influence."
Bob Holmes
You are forgetting about the Gaza Strip Palestinians. They aren't Jordanians at all. I expect that if you look closely, you'll see they are Egyptians (just like Yasser Arafat).
They scrounged on trhe equivalent of road kill, huh? How unromantic.
It's not that-it's the alien DNA that makes it hard.
I think Ill put the second in the flush file...
Ditto.
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