Talk:Human mitochondrial DNA haplogroups
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[edit] Graphics
I wrote Mr. Macaulay some time ago and asked him whether I may use their graphics for Wikepedia. He said it is OK as long as he and Mr. Richards are cited.
I uploaded the graphics and used it for the German article on "Mitochondrial Eve". I think it will fit well here.
http://commons.wikimedia.org/wiki/Image:MacaulayRichardsmtDNAtree.jpg
I also made a draft tree depicting the overall structure of the tree. The image of Richards and Macaulay looks very confunsing at first.
http://commons.wikimedia.org/wiki/Image:MtDNAtreeHuman.svg
Molgen 04:40, 10 December 2006 (UTC)
[edit] Status of L1 and L3
Perhaps we should state more clearly that L1 and L3 are no real (=monophyletic) haplogroups. Haplogroup L1a is not closer related to L1f as it is to V.
Molgen 04:40, 10 December 2006 (UTC)
[edit] Definition of mtDNA haplogroups
What is the definition of each of the mtDNA haplogroups? I.e. by which mutation it characterized? --Maruvkay 03:50, 13 August 2006
Your chart is a bit wrong. L2 comes from L1/L0 and L3 comes from L2.
L1 -> L2 ->L3 https://www3.nationalgeographic.com/genographic/
Mitochondrial Eve: The Mother of Us All
Ancestral Line: "Mitochondrial Eve"
Our story begins in Africa sometime between 150,000 and 170,000 years ago, with a woman whom anthropologists have nicknamed "Mitochondrial Eve."
She was awarded this mythic epithet in 1987 when population geneticists discovered that all people alive on the planet today can trace their maternal lineage back to her.
But Mitochondrial Eve was not the first female human. Homo sapiens evolved in Africa around 200,000 years ago, and the first hominids—characterized by their unique bipedal stature—appeared nearly two million years before that. Yet despite humans having been around for almost 30,000 years, Eve is exceptional because hers is the only lineage from that distant time to survive to the present day.
Which begs the question, "So why Eve?"
Simply put, Eve was a survivor. A maternal line can become extinct for a number of reasons. A woman may not have children, or she may bear only sons (who do not pass her mtDNA to the next generation). She may fall victim to a catastrophic event such as a volcanic eruption, flood, or famine, all of which have plagued humans since the dawn of our species.
None of these extinction events happened to Eve's line. It may have been simple luck, or it may have been something much more. It was around this same time that modern humans' intellectual capacity underwent what author Jared Diamond coined the Great Leap Forward. Many anthropologists believe that the emergence of language gave us a huge advantage over other early human species. Improved tools and weapons, the ability to plan ahead and cooperate with one another, and an increased capacity to exploit resources in ways we hadn't been able to earlier, all allowed modern humans to rapidly migrate to new territories, exploit new resources, and outcompete and replace other hominids, such as the Neandertals.
It is difficult to pinpoint the chain of events that led to Eve's unique success, but we can say with certainty that all of us trace our maternal lineage back to this one woman.
The L Haplogroups: The Deepest Branches
Ancestral line: "Eve" > L1/L0
Mitochondrial Eve represents the root of the human family tree. Her descendents, moving around within Africa, eventually split into two distinct groups, characterized by a different set of mutations their members carry.
These groups are referred to as L0 and L1, and these individuals have the most divergent genetic sequences of anybody alive today, meaning they represent the deepest branches of the mitochondrial tree. Importantly, current genetic data indicates that indigenous people belonging to these groups are found exclusively in Africa. This means that, because all humans have a common female ancestor, "Eve," and because the genetic data shows that Africans are the oldest groups on the planet, we know our species originated there.
Haplogroups L1 and L0 likely originated in East Africa and then spread throughout the rest of the continent. Today, these lineages are found at highest frequencies in Africa's indigenous populations, the hunter-gatherer groups who have maintained their ancestors' culture, language, and customs for thousands of years.
At some point, after these two groups had coexisted in Africa for a few thousand years, something important happened. The mitochondrial sequence of a woman in one of these groups, L1, mutated. A letter in her DNA changed, and because many of her descendants have survived to the present, this change has become a window into the past. The descendants of this woman, characterized by this signpost mutation, went on to form their own group, called L2. Because the ancestor of L2 was herself a member of L1, we can say something about the emergence of these important groups: Eve begat L1, and L1 begat L2. Now we're starting to move down your ancestral line.
Haplogroup L2: West Africa
Ancestral line: "Eve" > L1/L0 > L2
L2 individuals are found in sub-Saharan Africa, and like their L1 predecessors, they also live in Central Africa and as far south as South Africa. But whereas L1/L0 individuals remained predominantly in eastern and southern Africa, your ancestors broke off into a different direction, which you can follow on the map above.
L2 individuals are most predominant in West Africa, where they constitute the majority of female lineages. And because L2 individuals are found at high frequencies and widely distributed along western Africa, they represent one of the predominant lineages in African-Americans. Unfortunately, it is difficult to pinpoint where a specific L2 lineage might have arisen. For an African-American who is L2—the likely result of West Africans being brought to America during the slave trade—it is difficult to say with certainty exactly where in Africa that lineage arose.
Fortunately, collaborative sampling with indigenous groups is currently underway to help learn more about these types of questions and to possibly bridge the gap that was created during those transatlantic voyages hundreds of years ago.
Haplogroup L3: Out of Africa
Ancestral line: "Eve" > L1/L0 > L2 > L3
Your next signpost ancestor is the woman whose birth around 80,000 years ago began haplogroup L3. It is a similar story: an individual in L2 underwent a mutation to her mitochondrial DNA, which was passed onto her children. The children were successful, and their descendants ultimately broke away from the L2 clan, eventually separating into a new group called L3. You can see above that this has revealed another step in your ancestral line.
While L3 individuals are found all over Africa, including the southern reaches of sub-Sahara, L3 is important for its movements north. You can follow this movement of the map above, seeing first the expansions of L1/L0, then L2, and followed by the northward migration of L3.
Your L3 ancestors were significant because they are the first modern humans to have left Africa, representing the deepest branches of the tree found outside of that continent.
Why would humans have first ventured out of the familiar African hunting grounds and into unexplored lands? It is likely that a fluctuation in climate may have provided the impetus for your ancestors' exodus out of Africa.
The African Ice Age was characterized by drought rather than by cold. Around 50,000 years ago the ice sheets of northern Europe began to melt, introducing a period of warmer temperatures and moister climate in Africa. Parts of the inhospitable Sahara briefly became habitable. As the drought-ridden desert changed to savanna, the animals your ancestors hunted expanded their range and began moving through the newly emerging green corridor of grasslands. Your nomadic ancestors followed the good weather and plentiful game northward across this Saharan Gateway, although the exact route they followed remains to be determined.
Today, L3 individuals are found at high frequencies in populations across North Africa. From there, members of this group went in a few different directions. Some lineages within L3 testify to a distinct expansion event in the mid-Holocene that headed south, and are predominant in many Bantu groups found all over Africa. One group of individuals headed west and is primarily restricted to Atlantic western Africa, including the islands of Cabo Verde.
Other L3 individuals, your ancestors, kept moving northward, eventually leaving the African continent completely. These people currently make up around ten percent of the Middle Eastern population, and gave rise to two important haplogroups that went on to populate the rest of the world.
