September 30, 2009

What Are Haplogroups?

People have traditionally performed genealogical research by studying written documents. A new dimension has been added to genealogical research: the use of DNA. Each person has a "blueprint" in their body that contains information or instructions for the makeup and operation of their body. That blueprint is called DNA.

DNA is passed from parent to child in two ways. The Y-chromosome, that is passed from father to son, carries DNA information, and this information is referred to as Y-DNA. DNA information is also passed from mother to daughter and is known mtDNA. Y-DNA is used in genealogy because it is passed from father to son, and genealogical research is based on father-to-child relationships. Genealogists are beginning to use mtDNA, but its use isn't as widespread as that of Y-DNA.

Included in DNA is information about the origin of some of the person's ancestors. Humans are believed to have originated in Africa. The DNA of those ancient people was passed on to their children. However, occasional changes or mutations in DNA occurred, and the changes were also passed on to their descendants. As people spread over the earth, changes to DNA caused distinct patterns of DNA segments to appear. Today, those patterns are called haplogroups, and they give a general idea where particular genealogical lines came from tens of thousands of years ago.

The following chart shows how various Y-DNA haplogroups have separated from the original haplogroup that was in Africa, and the chart shows that haplogroups are a convenient way of identifying different genealogical lines. For example, many of the Leigh/Lee lines in the United Kingdom are of haplogroup RB1. Some of the Leigh/Lee lines in the UK, though, are of haplogroup I. The chart shows that the RB1 and I haplogroups originated from different people in different parts of the world, and this leads to the conclusion that the Leigh/Lee lines of haplogroup I are not related in a genealogical time frame to the Leigh/Lee lines of haplogroup RB1. Of course, haplogroup I is a large group of people, and not all of the Leigh/Lee lines in that haplogroup are related to each other.

Click the picture for a larger view of the chart.

This site focuses on the genealogy of people of haplogroup I. The ancient people who became haplogroup I migrated towards Scandinavia. This migration spread the DNA of the migrants among local folks. Further spreading of the haplogroup I DNA occurred during the ice age by migrations from Scandinavia to the Balkans, southern France, Iberia (present day Spain and Portugal) and Italy. During the middle ages, the Vikings invaded a wide area in Europe for about 200 years and spread their DNA throughout that area. As a result, haplogroup I is found today in many countries in addition to the Scandinavian countries, but that haplogroup is not common in most countries outside of Scandinavia.

The common ancestor between two Y-DNA donors

People doing genealogical research will have identified their most distant ancestor. This ancestor might be themselves, a father, a grandfather, a great grandfather, or someone further back in their family tree. The researchers may want to know whether or not that ancestor is related to other persons who often but not always have the same surname. In doing traditional genealogical research, the researchers try to obtain written records that will tell them if their ancestor is related to the other persons. However, such records may be difficult to locate and may not even exist. Since the Y-DNA markers do exist for male descendants of the two lines being investigated, the researchers can compare the Y-DNA markers of a male descendant from each line to determine if the two persons are related in some way. The use of Y-DNA can't give an exact relationship between two people, but it can tell if it is likely the two persons are related via a common ancestor. People who are likely related to each other will have most of their Y-DNA values the same. The fewer the values that are different, the more likely that the two persons have a common ancestor.

Let's consider an example of the use of Y-DNA to determine if two people might be related. This is a real-life example, but the names and locations have been changed to protect the privacy of the two persons, both of whom are still living.

John Leigh lives in Colorado. His great grandfather on his father's side immigrated from Wales to the United States. John has researched his great grandfather's Leigh line in Wales and has identified his earliest known Leigh ancestor. John had his DNA tested with the hope that someone in England will have Y-DNA that is a close match with his Y-DNA, thus giving him a general idea of where in England his earliest ancestor might have lived.

Michael Lee lives in Virginia. He has researched his Lee line back to his grandfather on his father's side, but he has not been able to extend his family tree past his grandfather. Michael assumes that the Lee ancestor who immigrated to the United States came from England, but Michael does not know who that ancestor was or when he came to the United States. Michael had his DNA tested with the hope that someone who has identified the Lee immigrant will have Y-DNA that matches with his Y-DNA.

After both men had completed their DNA testing, they were notified by the company doing the testing that they have a close match with each other and that it is likely the two men have an ancestor who is common to both of the men. The presence of a common ancestor is important because the common ancestor provides a link between the two lines, thus establishing a relationship between the lines. Michael was surprised at his close match with John, because he never suspected that his family tree might go into Wales. John explained to Michael that the common ancestor might have lived before John's branch went to Wales. If this is the case, Michael's family tree might not go into Wales, even though John's family tree does go into Wales.

As I mentioned at the beginning of this post, this example is a real-life example of how DNA testing gave new information that brought two distant relatives together and gave one of the relatives an understanding that his family tree might go into Wales. Now, because it is likely that John and Michael have a common ancestor, they can assist each other in further research into the identity and whereabouts of the Lee immigrant who came to the United States. To help Michael with his research, John has identified several places in his family tree in Wales where sidelines could have sprouted from his main line and later furnished the Lee immigrant.