Each cell of the human body contains organelles called mitochondria. Mitochondria were probably originally parasitic bacteria. Through evolution they became symbiotic with human cells, and finally an integral part of the cell. They help cells use oxygen. The DNA in mitochondria is separate from the DNA in the nucleus of the cell. The DNA in the nucleus is inherited from both parents, but the DNA in mitochondria is inherited only from the mother.

[youtube=http://www.youtube.com/watch?v=kS5qREISS-Q]

(YouTube: Gene Tree)

Mitochondrial DNA (mtDNA) passes to a woman’s children without any contribution from the father. That is, mtDNA does not recombine as nuclear DNA does. So, my mtDNA will match my mother and her children exactly. But, because I am male, I don’t pass on my mtDNA to my children. My sisters, on the other hand, will pass on our mtDNA unchanged to their children.

Mitochondrial DNA passes to each generation unchanged except for any mutations. The mutation rate for mtDNA is very low; perhaps one mutation at a given spot every 10,000-12,000 years. Therefore, mtDNA changes very slowly over many generations.

These characteristics make mtDNA useful to both geneticists and genealogists. It is a useful tool for understanding the remote origins of the human race, for tracing pre-historic population movements, and for matching people who belong to the same female line.

Continue…

Modern humans as well as extinct Neanderthals share a common ancestor who lived about 500 thousand years ago (~25 thousand generations).

Mitochondrial Eve

All humans living today descend in the female line from a woman nicknamed “Mitochondrial Eve.” This unknown woman probably lived in Africa, perhaps in Kenya, Tanzania or Ethiopia, probably about 150 thousand years ago (~7,500 generations). Mitochondrial Eve wasn’t the only human female in her generation — some scientists think that she belonged to a human population of about 2,000 people. The other women of her time certainly have descendants living today, but she was the only of them who has  female-line descendants living today. At different points in time, the female-line descendants of all her contemporaries left only sons, so their female lines became extinct.

Lara Clan

One of Mitochondrial Eve’s descendants in the female line was an unknown woman, nicknamed “Lara,” who lived in Africa, probably south of the Sahara Desert. Lara became the female line ancestor of everyone whose mtDNA belongs to Haplogroup L. Her descendants separated into groups now labeled L0 through L7.

The ancestor of the L3 group was an unknown woman who lived in the Middle East or Egypt about 100 thousand years ago (~5,000 generations). She has many descendants in Africa, but some of her descendants left Africa, so she became the female-line ancestor of all Asians, Europeans, aboriginal Australians and aboriginal Americans.

Humans exhibit less genetic diversity than would expected for our age as a species; far less than our closest primate cousins, the chimpanzees. Some scientists believe that humans nearly became extinct about 70 thousand years ago (~3,500 generations) when the Toba super-volcano erupted in Indonesia, triggering an environmental catastrophe. According to this theory, the human population might have been reduced to a few thousand people, perhaps as few as 1,000, thereby losing genetic diversity.

N Clan

The N clan is one of the branches of the L3 clan. It is believed to have originated with a woman who lived in Africa about 80 – 60 thousand years ago (~4,000 – 3,000 generations). She is the ancestor of nearly all Europeans and aboriginal Australians, and many Asians and aboriginal Americans.

R Clan

The R clan is one of the branches of the N Clan. The first woman with this mutation probably lived about 60 thousand years ago (~3,000 generations) in the Middle East. She became the maternal ancestor of six of the seven European haplogroups. (Haplogroup X is a sister rather than daughter clan of Haplogroup R.)

HV Clan

The HV clan originated about 30 thousand years ago (~1,500 generations) during the Upper Paleolithic Era (Old Stone Age). With the Ursula clan, they formed the Cro-Magnons, who produced the famous cave art in southern France. They shared territory with the Neanderthals, another branch of humans, who died out 27,000 years ago (~1.350 generations). During the last Ice Age the HV clan and Ursula clan retreated to what is now Spain, called the “Western Refugium.” Other European clans retreated to Italy, the Balkans and the Ukraine during the same period. The HV clan was the ancestral clan of both the Helena and Velda clans.

Velda Clan

The Velda clan is one of the branches of the HV clan. The unknown woman we call Velda (Scandinavia for “ruler”) probably lived about 17,000 years ago (~850 generations) in the limestone hills of Cantabria in northwest Spain. It would be a mistake to think of the Velda clan as ever having a separate identity as a group. There would have been nothing to set Velda apart from the other women of her tribe. Her relatives and her own immediate descendants undoubtedly married into other groups. Her female-line descendants would have fanned out into many tribes in the same region. The Basques are probably a surviving remnant of the Ursula and Velda clans.

When the glaciers melted, about 16 thousand years ago (~800 generations), humans once again spread out  through Europe. Descendants of the Velda clan migrated north along the coast of Spain into the plains of Gascony. One group of them reached the Norwegian seaboard, where they joined with people from arctic Russia to become the Sámi. Some of them, however, went south and are now found in Algeria. Because the Velda clan originated in the Spain, Haplogroup V is a marker for the spread of humans from Spain into Europe and Africa after the last Ice Age.

About 12 thousand years ago (~600 generations), members of the Velda clan (with the Ursula, Helena and Tara clans) reached the British Isles, probably coming across a land bridge that existed then. Farming came later, brought to Europe from Syria during the Neolithic Era, about 8,000 years ago (~400 generations). The so-called “races” emerged only about 5,000 years ago (~250 generations).

Until the European expansion of the 16th and 17th centuries, the Velda clan was nearly restricted to western, central and northern Europe where it accounts for about 4% of the population. It is most common among the Basques of Spain (12%) and the Skolt Sámi of Scandinavia (50%).

Each of us has inherited mitochondrial DNA (mtDNA), along with the mutations that have accumulated in our individual family lines. Geneticists can test for these accumulated mutations. Individual test results are called a haplotype or mitotype. People with the same cluster of mutations belong to the same haplogroup, and are descended from the same female line. There are 36 known mitochondrial haplogroups worldwide, with more being discovered as research advances.

Almost all Europeans belong to one of only seven haplogroups. This means that most Europeans are descended in the female line from one of seven different women. These women have been called the “Seven Daughters of Eve,” although they lived at widely different periods in history. Their descendants came to Europe at different times and spread throughout the continent. Of course, because we each have so many ancestors, not just our ancestors in the female line, all Europeans descend from each of these seven women many times over.

Geneticists identify each of the major haplogroups by a single letter. For example, H, J, K, T, U, V and X. Each of these letters, therefore, represents a family descended from a distant female ancestor. Subgroups within each haplogroup are represented by numbers. Further subgroups are represented by lower case letters. For example, U is a haplogroup, U5 is one of its subgroups, and U5a and U5b are further subgroups.

Oxford Ancestors, an English genetics lab, has assigned whimsical names to the founding mothers of the different haplogroups (which he calls “clans”). For example, the ancestor of haplogroup U is called Ursula, the ancestor of haplogroup V is called Velda, and so on.

Seven Daughters of Eve

According to Oxford Ancestors, the haplogroups most common in Europe are:

• See a diagram

Helena is by far the largest and most successful of the seven native clans with 41% of Europeans belonging to one of its many branches. It began 20 thousand years ago (~1,000 generations) with the birth of Helena somewhere in the valleys of the Dordogne and the Vezere, in south-central France. The clan is widespread throughout all parts of Europe, but reaches its highest frequency among the Basque people of northern Spain and southern France.

Remains that are said to be those of St. Luke the Evangelist show that he was a member of this clan. He was born in Syria and died in Thebes about 150 CE.

Another famous member was Marie Antoinette. Her earliest known maternal ancestor was Bertha von Pfullendorf, who died in 1198. Marie Antoinette’s DNA was tested as part of a project to validate the remains of her son, Louis VII.

The remains of the Russian royal family show that they also belonged to this clan. When the Russian royal family was murdered in 1918, their bodies were hastily disposed. In 1991, nine bodies were recovered from a shallow grave near Ekaterinburg, Russia. Experts obtained mtDNA samples from female-line relatives of Empress Alexandra, including Prince Philip. The samples matched the mtDNA extracted from the bones, proving that the bodies were the remains of the Romanovs. Further tests showed that Anna Anderson, a woman who claimed to be the Grand Duchess Anastasia, was in fact a Polish actress.

Jasmine is the second largest of the seven European clans after Helena and is the only one to have its origins outside Europe. Jasmine and her descendants, who now make up 12% of Europeans, were among the first farmers and brought the agricultural revolution to Europe from the Middle East around 8,500 years ago (~425 generations).

Katrine is a medium-sized clan with 10% of Europeans among its membership. Katrine herself lived 15 thousand years ago (~750 generations) in the wooded plains of northeast Italy, now flooded by the Adriatic, and among the southern foothills of the Alps. Her descendants are still there in numbers, but have also spread throughout central and northern Europe.

“The Ice Man,” also known as “Otzi,” was a member of this clan. He lived about 3350 BCE – 3300 BCE. His remains were discovered in 1991 in a glacier in the Italian Alps.

Tara includes slightly fewer than 10% of modern Europeans. Its many branches are widely distributed throughout southern and western Europe with particularly high concentrations in Ireland and the west of Britain. Tara herself lived 17 thousand years ago (~850 generations) in the northwest of Italy among the hills of Tuscany and along the estuary of the river Arno.

Nicholas II, last Emperor of Russia, was a member of this clan, as was Jesse James.

Ursula is the oldest of the seven European clans. It was founded about 45 thousand years ago (~2,250 generations) by the first modern humans (Homo Sapiens) as they established themselves in Europe. Dr. Brian Sykes, Oxford University, believes Ursula was born in a shallow cave cut into the cliffs of what is now Mount Parnassus, close to what became Delphi. Her female-line descendants are common among both white Europeans and black Africans — she lived at a time before the emergence of the so-called “races.” Today, about 11% of modern Europeans are the direct maternal descendants of Ursula. The clan is particularly well represented in western Britain and Scandinavia.

“Cheddar Man,” whose remains were discovered in a cave in England, was a member of the Ursula Clan. He died about 9,000 years ago (~450 generations).

Velda is the smallest of the seven European clans containing only about 4% of native Europeans. Velda lived 17 thousand years ago (~850 generations) in the limestone hills of Cantabria in northwest Spain. Her descendants are found nowadays mainly in western and northern Europe. They are surprisingly frequent among the Skolt Sámi (Lapps) (50%) of Scandinavia and the Basques (12%) of Spain.

Xenia is the second oldest of the seven European clans. It was founded 25 thousand years ago (~1,250 generations) by the second wave of modern humans, Homo Sapiens, who established themselves in Europe, just prior to the coldest part of the last Ice Age. Today around 7% of native Europeans are in the clan of Xenia. About 1% of Native Americans are also in the clan of Xenia.

An Anglo-Saxon skeleton from the 11th century was discovered at Norwich Castle in England and shown to be a member of this clan.

More Information

• Brian Sykes. The Seven Daughters of Eve (2001).
• Wikipedia, Human Mitochondrial DNA Haplogroups.

Continue …

Mitochondrial DNA is long, circular strand of DNA. (Bacterial DNA is also circular.) It is composed of 16,569 smaller units, called base pairs. Each base pair is composed of two nucleotides. There are only four possible nucleotides — adenine (A), thymine (T), cytosine (C) and guanine (G). Each nucleotide has a complementary nucleotide. So, along the strand of DNA, adenine always appears paired with thymine, and cytosine always appears paired with guanine. Because each nucleotide can only appear with its complement, it is not necessary to report both sides of the chain. So, the DNA chain can be expressed as a chain of nucleotides, for example, GATCACAGGT…

Taking a DNA Sample

A DNA sample consists of human cells. The most common method of taking a sample is to use a cotton swab to brush the inside of a person’s cheek. Some labs use mouth wash or chewing gum. Older procedures often required a blood sample. The sample is then sent to a lab for testing.

Lab Procedure

When a lab tests mtDNA, it looks for mutations. Mutations can take three forms:

1. Substitutions — the base pair at a particular location can change. This is the most common form of mutation, and the only form I discuss here.

2. Deletions — the base pair at a location can be deleted.

3. Insertions — a new base pair can be inserted between existing locations.

To find mutations, the lab determines which nucleotides appear at each location on the mtDNA molecule. To save time, it tests only hyper-variable segments, that is, areas where mutations are most likely to occur. One common segment to test is HVS-1, which starts at base pair 16,001 and ends at base pair 16,568. Another common region to test is HVS-2, which starts at base pair 1 and ends at base pair 574. (Note: the actual range for each hyper-variable region varies slightly from lab to lab.)

Understanding Test Results 

The convention for reporting mtDNA results is not difficult, but it requires some explanation:

The lab compares test results to the Cambridge Reference Series (CRS). The reference series is arbitrary. It is the mtDNA sequence for the first person whose mtDNA was analyzed, not the original sequence for homo sapiens.

Locations on the DNA molecule are numbered. As a shorthand, the lab uses location numbers, then adds the abbreviation for the nucleotide at each location. The nucleotides are abbreviated as A (adenine), T (thymine), C (cytosine) and G (guanine). For example, in this shorthand 16270T means the nucleotide at location number 16,270 is thymine.

Each nucleotide can only appear with its complement, so the lab reports only one nucleotide at each location. For example, 16270T means that the nucleotide at location number 16,270 is thymine, which is understood to be one side of a base pair composed of thymine and its complement adenine.

The lab reports only differences from the Cambridge Reference Series. If the result at a particular location matches the reference series, it is not reported. If it is different from the series, it is reported. For example, a test result of 16270T means the test sample matches the reference series, except at location number 16,270. The reference series has a cytosine/guanine base pair at this location, but the test subject has thymine/adenine.

My mtDNA Test Results

The test results are:

16270T 16292A 16298C 00072C 00195C 00263G 00309.1C 00315.1C (Haplogroup V)

These codes are shorthand for the mutations in my individual family line. The three numbers mean that my mtDNA matches the standard reference series, except at those locations. The letters indicate the difference. The reference series has 16270C (cytosine/guanine), 16292C (cytosine/guanine) and 16298T (thymine/adenine). In my mtDNA, those locations are 16270T (thymine/adenine), 16292A (adenine/thymine) and 16298C (cytosine/guanine). Only the left-hand nucleotide of the base pair is reported, because its complement can be assumed.

Haplogroup Assignment

I belong to Haplogroup V2, although that was not clear initially. I had my mtDNA tested by Oxford Ancestors in 1999. They got it wrong. The error came to light in 2007 when I was re-tested at Family Tree DNA.

Based on my (erroneous) test results, Oxford Ancestors (1999) predicted that I belong to Haplogroup U5b. Their prediction was problematic. Both Haplogroups H and U match the reference series at HVR-1. To distinguish between them, HVR-2 must be tested. I was tested only at HVR-1. Nevertheless, a mutation at 16270 is a defining characteristic (“motif”) of subgroup U5, so, it seemed likely that I would be U5. (Not U5b — I do not have a mutation at 16189, which is the motif for U5b). (See Macaulay, Table of Haplogroup Motifs).

Family Tree DNA (2007) disagreed, and on the basis of their tests, assigned me to Haplogroup V. Oxford Ancestors then explained, “A mutation at position 270 is characteristic of clade U and a position at 298 is a characteristic of clade V. It was always believed in the early days that as clade U was the more common that it over rode the clade V, but more recent research has in fact confirmed that this is not in fact the case and the a [sic] mutation at position 298 is the defining one and you are therefore more correctly assigned to clade V and indeed this is where we would now place you.” (Personal Communication, October 11, 2007).

My haplogroup assignment could change again, slightly. It is not possible to distinguish between Haplogroups Pre-V and V on the basis of results only from HVR-1 and HVR-2. About 23% of those assigned to Haplogroup V actually belong to Haplogroup Pre-V.

Haplogroup V evolved from Haplogroup Pre-V, which evolved from Haplogroup HV. HV has 14766C, which matches the standard reference series (which is in Haplogroup H). Mutations 16298 T>C and 00072 T>C define Pre-V. Then,5904 C>T, leads further into Pre-V. Finally, 04580 G>A defines Haplogroup V.

The full motif for Haplogroup V is:

16298C, 00072C, 04580A, 14766C, 15904T

According to Whit Athey, when Family Tree DNA does RFLP tests for Haplogroup V, they check 04580, 07028 and 14766.04580A defines Haplogroup V, but 14766C assures that the haplotype lies somewhere in the HV complex, and 07028T confirms that it is not in H.

Continue …