Modern Humans Came Out Of Africa, "definitive" Study Says

[Jun]

James Owen

for National Geographic News

July 18, 2007

 

We are solely children of Africa—with no Neandertals or island-dwelling "hobbits" in our family tree, according to a new study.

 

Scientists who compared the skulls and DNA of human remains from around the world say their results point to modern humans (Homo sapiens) having a single origin in Africa.

 

The study didn't find any evidence to suggest that human species living elsewhere in the world contributed to our direct ancestors' make-up.

 

A team led by Andrea Manica at the University of Cambridge, England, combined analysis of global genetic variations with comparisons of more than 6,000 skulls from more than a hundred ancient human populations.

 

The team found that loss of genetic diversity was very closely mirrored by reduced physical variation the farther away people lived from Africa.

 

Only Out of Africa

 

The new data support the single origin, or "out of Africa" theory for anatomically modern humans, which says that these early humans colonized the planet after spreading out of the continent some 50,000 years ago.

 

In the past, experts have also argued a "multiregional" theory, which held that Homo sapiens arose from different human populations in different areas of the world.

 

"The origin of anatomically modern humans has been the focus of much-heated debate," lead author Manica said.

 

"We have combined our genetic data with new measurements of a large sample of skulls to show definitively that modern humans originated from a single area."

 

Previous studies have found that genetic differences in human populations can be explained by distance from Africa.

 

The new study also looked at 37 measurements from male and female skulls from around the world. The chosen skulls were all less than 2,000 years old, making them better preserved and more likely to give accurate measurements than older skulls.

 

Many skull features were determined by the different environments where the humans had lived.

 

But distance from Africa was still found to account for up to 25 percent of variation in the features.

 

'Remarkable' Similarity

 

The researchers made sure that the DNA analysis used the same framework as the analysis for the skulls—so the two could be fully compared, Manica said.

 

"I would argue we had two independent shots at getting the same answer, and remarkably, the answer is exactly the same," he added.

 

The lowest amount of variation was found in ancient populations from South America and Australia, the two main inhabited regions most remote from Africa.

 

The study team, writing in the latest issue of the journal Nature, argues that this low variation in remote regions relative to Africa would be expected if Homo sapiens arose solely in Africa.

 

That's because populations built up genetic and physical diversity for some 150,000 years before the fossil record suggests the first pioneers started spreading elsewhere.

 

But it wasn't until between about 20,000 and 30,000 years ago that modern humans reached South America and Australia, the team noted.

 

"The more you move away from that center of diversity where you started, the less diversity you have," Manica said.

 

This pattern was remarkably consistent globally, the researchers found.

 

The study places the original roots of modern humans in south-central Africa. In the middle of this region lies the Great Rift Valley—often referred to as the "cradle of humanity."

 

Some researchers believe that modern humans are at least in part the product of non-African species descended from Homo habilis, which left Africa at least 1.5 million years ago.

 

Such groups include the Neandertals of Europe and western Asia, archaic human types in eastern Asia and Australia, and perhaps even the controversial hobbit humans from the Indonesian island of Flores.

 

'No Other Source'

 

"What we can confidently say is that there has not been a wave [of anatomically modern humans] starting from somewhere else, because then you'd find a second area with more variability," Manica said.

 

What Manica can't say is "that matings with the Neandertals never ever happened, but if it did happen, none of the descendants stayed around." Effectively, any mating had no contribution whatsoever to modern humans, he added.

 

Anthropologist Erik Trinkhaus of Washington University in St. Louis, Missouri, has found fossil evidence suggesting that Homo sapiens and Neandertals did interbreed. Trinkhaus is critical of the latest findings.

 

Certain genetic and anatomical traits "cannot be explained as a simple and complete expansion of modern humans out of Africa," he said.

 

"The idea that humans get more uniform further from Africa is simply ludicrous," he added, noting that modern-day Chinese and Australian Aborigines look no more similar to each other than do Africans and Europeans.

 

Fred Smith, an anthropologist at Loyola University of Chicago who is unaffiliated with the research, agrees that the findings confirm there is an African origin for modern humans.

 

Smith nevertheless argues that the study is not at odds with the idea he first proposed in 1989 that there was "some low-level assimilation of archaic peoples into these modern populations."

 

And Charles Roseman, of the University of Illinois at Urbana-Champaign, said: "It could very well be that there was a recent out-of-Africa expansion, coupled with some either small or large amount of genetic exchange with humans outside of Africa."

 

http://news.nationalgeographic.com/news/20...n-origin_2.html

[Grandpa Harley]

Out of Africa is something of an article of faith. There are other equally good studies that get ignored due to political issues. It's a bit like being a Holocaust Denier to deny other studies air time, but they don't...

[Vigile]

Gramps, are you saying that other studies offer that not all humans have a common ancestor? There was another discussion here last year I think where a member cited studies saying that Australian aborigines and some tribes in the Amazon region (if I remember right) had a significantly different DNA structure. It was all quite controversial, but interesting.

[Grandpa Harley]

IIRC we do have a common ancestor, and some went into Africa then came out again, so there was a divergence. Not enough for full blown speciation, but enough to show up. It was a pretty good study, from the stats... I'll have a poke around see if I can dig something up more than my memory (which is shot)

[Grandpa Harley]

From memory, one of the objections to multiregionalism is that there is, inherently, a concept of 'purity of lineage' and the '5 root races' that informed what passed for science in Nazi Germany, which was no great bench mark for anything...

[Sceadugenga]

While 'Out of Africa' is still pretty much the best theory going, there is still alot of debate about the actual nature of Humanity's spread out of Africa - was it a one off event, waves, or even how much 'reverse' contact occured?

[Taphophilia]

Gramps, are you saying that other studies offer that not all humans have a common ancestor? There was another discussion here last year I think where a member cited studies saying that Australian aborigines and some tribes in the Amazon region (if I remember right) had a significantly different DNA structure. It was all quite controversial, but interesting.

 

I remember that discussion. Basically, the poster was using arguments to support The Bell Curve.

 

The Australian aborigines share a genetic marker with peoples along the pacific rim, mongolia and certian American Indian tribes of the Western US, chiefly Navaho.

 

Amazonians and almost all aborigonal North and South Americans share the same genetic marker. The genetic marker they share is a branch off of another genetic marker found in central asia.

[Guest Kat Mon Dieu]

Gramps, are you saying that other studies offer that not all humans have a common ancestor? There was another discussion here last year I think where a member cited studies saying that Australian aborigines and some tribes in the Amazon region (if I remember right) had a significantly different DNA structure. It was all quite controversial, but interesting.

 

I remember that discussion. Basically, the poster was using arguments to support The Bell Curve.

 

The Australian aborigines share a genetic marker with peoples along the pacific rim, mongolia and certian American Indian tribes of the Western US, chiefly Navaho.

 

Amazonians and almost all aborigonal North and South Americans share the same genetic marker. The genetic marker they share is a branch off of another genetic marker found in central asia.

 

Hello,

 

I just wanted to add a bit to this discussion. Theories are only meant to be the best explanation till a better explanation comes along. Unlike religious dogma which accepts only one interpretation. I generally accept the OUT OF AFRICA as being prtty iron clad with room for expansion and exception. Adding to what you said about the Aboriginals The Tierra Del Fuego Indians of South America (now extinct) Looked exactly like their cousins in Australia. They genetically speaking are almost indentical. Sharing no other genetics with any other tribes of South America. The last two women of that tribe died out back in the 1980's. I saw a documentary on them some time ago. The implications of this is that they most likely navigated to south america from Australia over 50,000 years ago.

 

Human beings are quite nomadic and most likely have never stayed put for very long since we became meat eaters and grew large brains. So there may be some thing to the proposal that there may have been some reflux back into africa by Neanderthal. Most evidence that I have seen suggests that there was more than one migration out of africa. However Africa certainly seems to be the Cradle of Homo Sapiens.

 

There are several projects going on by various scientific groups doing mapping of mitochondrial DNA and Y chromosomes. Tracing them back to known locations and populations from before the last Ice Age. I can find the link if anyone is interested in tracing their true origins. It costs about a hundred bucks per test.

 

http://www.whydoesgodhateamputees.com/

 

Kat Mon Dieu

[LithaB]

Interesting, do you suppose I could get away with calling myself African-American now?

[Grandpa Harley]

There's enough horror attached to my paternal name and enough mystery attached to my maternal line that I don't think I want to know the 'truth'

[jasonwhatever]

Well, Bible thumpers will say that this all discredits evolution. It supports that we came from Adam and Eve.

 

Several problems with that exist. The dna and physical evidence shows humans inhabiting far sections of the world over 50,000 years ago AT LEAST. If you follow the Bible timeline, there is no way that it allows for humans to have existed that long ago. According to the Bible, humans were created about 6-7000 years ago.

 

Second, the story of the Tower of Babel then cannot be correct, because it says that all people were in one place at that time, the tower. And from there God scattered them across the earth. This is not possible either since if you believe The Bible, the scattering from the tower had to have occured after man was created (duh), which means that it occured well under 7000 years ago. The dna evidence shows humans were already abroad across the earth.

 

Third, the Bible teaches that humans started in the middle east, in the garden of Eden, in what became known as Mesopotamia. Mesopotamia is certainly not south-central Africa.