Genetic genealogy

Genetic genealogy is the use of DNA testing in combination with traditional genealogy and traditional genealogical and historical records to infer relationships between individuals. Genetic genealogy involves the use of genealogical DNA testing to determine the level and type of the genetic relationship between individuals. This application of genetics became popular with family historians in the first decade of the 21st century, as tests became affordable. The tests have been promoted by amateur groups, such as surname study groups, or regional genealogical groups, as well as research projects such as the genographic project. As of 2013 hundreds of thousands of people had been tested. As this field has developed, the aims of practitioners broadened, with many seeking knowledge of their ancestry beyond the recent centuries for which traditional pedigrees can be constructed.

History

George Darwin, son of Charles Darwin, was the first to estimate the frequency of first-cousin marriages

The investigation of surnames in genetics can be said to go back to George Darwin, a son of Charles Darwin. In 1875, George Darwin used surnames to estimate the frequency of first-cousin marriages and calculated the expected incidence of marriage between people of the same surname (isonymy). He arrived at a figure between 2.25% and 4.5% for cousin-marriage in the population of Great Britain, higher among the upper classes and lower among the general rural population.

Surname studies

One famous study examined the lineage of descendants of Thomas Jefferson’s paternal line and male lineage descendants of the freed slave, Sally Hemmings.

Bryan Sykes, a molecular biologist at Oxford University tested the new methodology in general surname research. His study of the Sykes surname obtained results by looking at four STR markers on the male chromosome. It pointed the way to genetics becoming a valuable assistant in the service of genealogy and history.

Direct to consumer paternity testing

The first company to provide direct-to-consumer genetic DNA testing was the now defunct GeneTree. However, it did not offer multi-generational genealogy tests. In fall 2001, GeneTree sold its assets to Salt Lake City-based Sorenson Molecular Genealogy Foundation (SMGF) which originated in 1999. While in operation, SMGF provided free Y-Chromosome and mitochondrial DNA tests to thousands. Later, GeneTree returned to genetic testing for genealogy in conjunction with the Sorenson parent company and eventually was part of the assets acquired in the Ancestry.com buyout of SMGF.

The genetic genealogy revolution

In 2000, Family Tree DNA, founded by Bennett Greenspan and Max Blankfeld, was the first company dedicated to direct-to-consumer testing for genealogy research. They initially offered eleven marker Y-Chromosome STR tests and HVR1 mitochondrial DNA tests. They originally tested in partnership with the University of Arizona.

The publication of The Seven Daughters of Eve by Sykes in 2001, which described the seven major haplogroups of European ancestors, helped push personal ancestry testing through DNA tests into wide public notice. With the growing availability and affordability of genealogical DNA testing, genetic genealogy as a field grew rapidly. By 2003, the field of DNA testing of surnames was declared officially to have “arrived” in an article by Jobling and Tyler-Smith in Nature Reviews Genetics. The number of firms offering tests, and the number of consumers ordering them, rose dramatically.

The Genographic Project

Main article: Genographic Project

The original Genographic Project was a five-year research study launched in 2005 by the National Geographic Society and IBM, in partnership with the University of Arizona and Family Tree DNA. Its goals were primarily anthropological. The project announced that by April 2010 it had sold more than 350,000 of its public participation testing kits, which test the general public for either twelve STR markers on the Y-Chromosome or mutations on the HVR1 region of the mtDNA.

In 2007, annual sales of genetic genealogical tests for all companies, including the laboratories that support them, were estimated to be in the area of $60 million (2006).

Typical customers and interest groups

The earliest test takers were customers most often those who started with a Y-Chromosome test to determine their father's paternal ancestry. These men often took part in surname projects. The first phase of the Genographic project brought new participants into genetic genealogy. Those who tested were as likely to be interested in direct maternal heritage as their paternal. The number of those taking mtDNA tests increased. The introduction of autosomal SNP tests based on microarray chip technology changed the demographics. Women were as likely as men to test themselves. Further, Ancestry.com's simplification of matching brought a larger number of test takers, though the validity of their DNA matching and accompanying genealogy pairing were questioned.

Citizen science and ISOGG

Further information: International Society of Genetic Genealogy and Y-chromosome haplogroup trees

Members of the growing genetic genealogy community have been credited with making useful contributions to knowledge in the field.

One of the earliest interest groups to emerge was the International Society of Genetic Genealogy (ISOGG). Their stated goal is to promote DNA testing for genealogy. Members advocate the use of genetics in genealogical research and the group facilitates networking among genetic genealogists. Since 2006 ISOGG has maintained the regularly updated ISOGG Y-chromosome phylogenetic tree. ISOGG aims to keep the tree as up-to-date as possible, incorporating new SNPs. However, the tree has been described by academics as not completely academically verified, phylogenetic trees of Y chromosome haplogroups.

Uses

Mitochondrial DNA and direct maternal lineages

mtDNA testing involves sequencing or testing the parts of the hypervariable region (HVR1 or HVR2) or the complete mitochondrial genome (mtGenome). An mtDNA test that only tests part of the hypervariable region may also include the additional SNPs needed to assign people to a maternal haplogroup.

Direct paternal lineages

Y-Chromosome DNA (Y-DNA) testing involves short tandem repeat (STR) and, sometimes, single nucleotide polymorphism (SNP) testing of the Y-Chromosome. The Y-Chromosome is present only in males and only reveals information on the strict-paternal line. These tests can provide insight into the recent (via STRs) and ancient (via SNPs) genetic ancestry. A Y-chromosome STR test will reveal a haplotype, which should be similar among all male descendants of a male ancestor. SNP tests are used to assign people to a paternal haplogroup, which defines a much larger genetic population.

Biogeographical and ethnic origins

Further information: Biogeographic ancestry and Population genetics

Additional DNA tests exist for determining biogeographical and ethnic origin, but these tests have less relevance for traditional genealogy.

Preliminary results from a study by Pierre Zalloua of the American University of Beirut and Spencer Wells were published in the October 2004 issue of National Geographic. One of its conclusions is that "more than half of the Y-Chromosome lineages that we see in today's Maltese population could have come in with the Phoenicians."

Human migration

Main article: Human migration

Genealogical DNA testing methods are in use on a longer time scale to trace human migratory patterns. For example, they determined when the first humans came to North America and what path they followed.

For several years, researchers and laboratories from around the world sampled indigenous populations from around the globe in an effort to map historical human migration patterns. The National Geographic Society's Genographic Project aims to map historical human migration patterns by collecting and analyzing DNA samples from over 100,000 people across five continents. The DNA Clans Genetic Ancestry Analysis measures a person's precise genetic connections to indigenous ethnic groups from around the world.

See also

Main article: List of genetic genealogy topics

• Allele
• Allele frequency
• Citizen science
• Electropherogram
• Family name
• Genealogical DNA test
• Genealogy
• Genetic recombination
• Haplogroup
• Haplotype
• Human mitochondrial DNA haplogroups
• Human Y-chromosome DNA haplogroups
• Human mitochondrial genetics
• Human genetic clustering
• Most recent common ancestor
• Short tandem repeat (STR)
• Single nucleotide polymorphism (SNP)
• Y-STR (Y-chromosome short tandem repeat)
• Y-chromosome haplogroups by populations
• Non-paternity event

Further reading

Books

• Early book on adoptions, paternity and other relationship testing. Carmichael is a founder of GeneTree.
• Survey of major populations.
• Out of date but still worth reading.
• Early guide for do-it-yourself genealogists.
• Guide to the subject of family medical history and genetic diseases.
• Names the founders of Europe’s major female haplogroups Helena, Jasmine, Katrine, Tara, Velda, Xenia, and Ursula.

Documentaries

• PBS (2003). The Journey of Man DVD. Broadcast aired in January 2003, Spencer Wells, host.

Journals

External links and resources

• International Society of Genetic Genealogy
• MSNBC – Genetic genealogy links from MSN