By Victor Greto
When you look at Celeste Williams-Hughes, you’re looking at 160,000 years of human history.
That history is buried in her DNA, specifically in its 569-letter mitochondrial sequence, a mish-mash of the four nucleotides encoded in each cell of her body.
Her chemical building blocks show that 160 millennia ago her ancestors lived about 8,000 miles away in east Africa. But the DNA also shows how over the next 140,000 years a branch of her descendants ended up in Scandinavia, probably Finland.
Celeste discovered her ancient heritage two months ago, after sending in DNA samples to the National Geographic Genographic project. Begun in April 2005, the genographing project is a five-year genetic anthropology study that is mapping human migration patterns by collecting and analyzing DNA samples from hundreds of thousands of people around the world. The more information the project gathers, the more specific it can be about your particular ancestry.
Emerging science may one day make it possible for us to change anything we want about ourselves, says Spencer Wells, population geneticist and National Geographic Genographic project director.
“We now have the tools to change our genome,” he said. “We’re going into the future at an incredible pace. Being the most intelligent species, we should know something about where we come from.”
Genetic markers — mutations that are passed on — on mitochondrial DNA passed from mother to daughter and Y-chromosomes passed from father to son are used to trace each person’s lineage.
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Before her DNA test, Celeste had done more traditional genealogical research.
“We thought we were Irish, but found out we were English and German,” Celeste said.
Now she knows that, ultimately and like the rest of us, she’s really from Africa.
Just like Jim Brannon.
The strands of his DNA wind back at least 60,000 years, to a man who also lived in east Africa.
Brannon’s lineage was traced through his Y-chromosome, which only men have, and which he inherited intact from his father, who inherited it from his, all the way back to Africa.
Like Celeste’s ancestors, Brannon’s left Africa about 50 millennia ago. But his DNA evidence shows that as recently as 10,000 years ago, they probably were farming in the Mediterranean region.
Brannon also already had done more traditional genealogical research.
“Apparently,” he said, “my paternal line drove directly from the Rift Valley into Egypt, across the Sinai, then migrated into Greece. So, the best I can surmise is that after establishing civilization, law and democracy, my forefathers headed to the British Isles and on to the Delaware Valley to crusade against slavery.”
Look in the mirror. You, too, are looking at the results of 160,000 years of human history.
While humans trace their history and prehistory back 60 millennia, Celeste’s and Jim’s ancestors — and yours, too, according to the DNA evidence — can be traced to the same 160,000 year old mother. The Y chromosome DNA can be traced back only as far as 60,000 years.
Scientists have nicknamed these two ancient people “Mitochondrial Eve” and “Y-chromosome Adam.” They have been unable to trace beyond that.
Think of all the lineages that exist today as ripples in a lake, said project director Wells.
“We trace back and triangulate those ripples to find out exactly where the rock entered the water,” he said.
More than 85 percent of those who have contributed their DNA to this project are from North America, Wells said. But the project also has sent researchers to 10 regional centers around the world to collect DNA samples from indigenous populations, some of whom aren’t happy about the project because it collides with their own traditional stories of origin.
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Wells, a National Geographic explorer-in-residence and the instigator of the genographic project, argues that a group of as little as 2,000 human beings who lived in east Africa engendered the six and a half billion of us living today.
Among anthropologists, this is called the single-origin hypothesis.
“We were on the brink of extinction,” Wells has written. “And then something happened.”
What happened, circa 50,000 years ago — “perhaps [due to] a few small genetic mutations,” Wells suggested — has been called “The Great Leap Forward.”
These folks were just as smart and adaptable as we are. Like us, they could think abstractly, plan ahead, make tools, create art and play games. They buried their dead, and could tell each other jokes.
But climate change helped redirect human history and eventually populated the world.
The scientific consensus agrees that the ancestors of human beings began walking about 4-5 million years ago. By about 2 million years ago, bipedal creatures, called homo erectus, had migrated outside of Africa.
By about 200,000 years ago, homo sapiens (that’s us) had evolved.
According to the single-origin hypothesis, homo sapiens remained in Africa until about 50,000 to 60,000 years ago.
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Not all scientists agree with the single-origin hypothesis.
Another scientific consensus views the same evidence and theorizes what is called the multi-regional theory.
One of those who does is Karen Rosenberg, a paleoanthropologist at the University of Delaware.
According to this theory, modern homo sapiens evolved from homo erectus everywhere, not just in Africa.
These “archaic humans” include, most famously, the Neandertals, who had settled half a million years ago in what is now Europe.
Rosenberg believes that these folks traveled and interbred with other homo sapiens throughout the region, in and out of Africa.
Scientists who subscribe to the single-origin hypothesis do not believe that Neandertals were the same species — defined as one that is unable to breed with another — as modern homo sapiens.
“I think the fossil record we have so far supports the idea that people have been evolving all over the world as one single species that didn’t become genetically isolated from one another,” Rosenberg said. “There may have been a higher population in Africa, but they weren’t a different species. They may have been physically different but not genetically distinct.”
Wells, however, argues that evidence for the single-origin theory is “overwhelming.”
So far, all the DNA evidence he’s gathered points to Mitochondrial Eve and Y-chromosome Adam. There have been no exceptions.
“Maybe we’ll find something unusual,” Wells said. “But either theory shows that people ultimately go back to Africa.”
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The genographic project also shows how humans changed genetically during prehistory.
Every once in a great while, a mutation — a random, natural change — occurs in a DNA sequence, which is then passed on, but which retains all of its past history.
Each branch or lineage may be traced because that random genetic mutation or marker was passed on.
Brannon’s DNA-based lineage shows a series of at least four mutations, which tells scientists where his ancestors migrated. They base this on comparisons and contrasts with thousands of other DNA samples.
Brannon’s most distant traceable male ancestor probably lived in northeast Africa near Tanzania.
Why did some branches, and not others, of this ancient person’s descendants decide to move?
Because about 50,000 years ago, along with the “Great Leap Forward,” the ice age began to recede, bringing to Africa a warmer, moister climate. What once was a desert became a savanna, and as animals spread north, so did some of our ancestors who hunted them.
Brannon’s specific lineage wanders up to northeast Africa, and then splits into two different groups: one that remained partly in Africa while part settled at the Mediterranean; and another that migrated into Asia.
At first, Brannon’s ancestors stayed put.
Then, 30,000 years ago, they moved north into the Middle East, perhaps following the herds of mammals that also migrated north. People’s hair and skin and other characteristics began to change then, too, scientists say, probably in response to different climates and levels of sunshine.
Over thousands of years, the climate became colder again and parts of Africa returned to desert, effectively blocking off an easy return home.
For thousands of years, Brannon’s ancestors stayed in the Middle East. About 10,000 years ago, however, they had found their way west into the Mediterranean and became some of the first farmers.
“These ancient farmers, your ancestors,” Brannon’s genographic report reads, “helped bring the Neolithic Revolution into the Mediterranean.” Neolithic (“Old Stone Age”) Revolution indicates the beginning of large-scale farming.
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Celeste’s DNA story begins much earlier, and includes seven mutations.
One branch of Celeste’s most ancient lineage remained in east Africa; another branch settled in west Africa, and is probably the progenitor of most African-Americans. Parts of a third branch, however, moved north and eventually out of Africa.
Like Brannon’s line, Celeste’s line moved north as the glaciers receded more than 50 millennia ago. From north Africa, the line branched out in several directions. Some lines remained in Africa.
Others, including Celeste’s, kept migrating north. One branch of this group’s descendants followed a coastal route eastward, and made it all the way to Australia and Polynesia. Celeste’s line moved north rather than east and left the African continent via the Sinai Peninsula.
A branch of this line eventually made its way into the eastern Mediterranean and western Asia, where they likely coexisted for a time with Neandertals.
This group spawned many other lineages, which spread across much of the rest of the world, and are found throughout Asia, Europe, India and the Americas.
Some folks in this migration moved south, back into northern Africa. Others went west across present-day Turkey and north across the Caucasus Mountains of Georgia and southern Russia. Others headed east into the Middle East, and on to central Asia.
The lines get very complicated and mixed, and spread in many directions. But Celeste’s line headed north into Scandinavia. This is where the genetic mutations stop telling us anything more about her.
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Brannon and Celeste are only two of dozens of area residents figuring out their prehistoric lineages.
“There’s an immutable bond between you and all your paternal relations,” said Peter Christy of Wilmington, who sent his DNA in to both the National Geographic and to FamilyTreeDNA.com.
“What interferes with this is that humans think in family relationships, and DNA is oblivious to this. We’re all connected at some point.”
Brannon said genographing shows that history matters.
“I think this will help stop the never-ending finger-pointing,” he said. “The root is the important thing. We all started from the same common stock.”