Genetic genealogy

Genetic genealogy is the application of genetics tosequences of DNA pairs of individuals in order to
traditional genealogy. Genetic genealogy involvesestimate the probability that they share a
the use of genealogical DNA testing to determinecommon ancestor in a genealogical time frame
the level of genetic relationship between individuals.and, through the use of a Bayesian model
The investigation of surnames in genetics can bepublished by Bruce Walsh, to estimate the number
said to go back to George Darwin, son of thegenerations separating the two individuals from
founder of evolutionary science. In 1875, Darwintheir most recent common ancestor.
fils (french "son") used surnames to estimate theY-DNA research involves short tandem repeat
frequency of first-cousin marriages and calculated(STR) and, sometimes, single nucleotide
the expected incidence of marriage betweenpolymorphism (SNP) testing of the
people of the same surname (isonymy). HeY-chromosome. The Y-chromosome is present
arrived at a figure between 2.25% and 4.5% foronly in males and reveals information on the strict
cousin-marriage in the population of Great Britain,paternal line. These tests can provide insight in the
with the upper classes being on the high end andrecent (via STRs) and ancient (via SNPs) genetic
the general rural population on the low end.ancestry. A Y-chromosome STR test will reveal a
Admittedly, this was a pretty crude effort byhaplotype, which should be similar among all male
modern scientific standards but quite innovativedescendants of a male ancestor. SNP tests are
for its era. The next stimulus toward usingused to assign people to a paternal haplogroup,
genetics to study family history had to wait untilwhich defines a genetic population.
the 1990s, when certain locations on the YmtDNA research involves sequencing the HVR-1
chromosome were identified as being useful forregion, HVR-2 region or both. A mtDNA test can
tracing male-to-male inheritance.also be used to assign people to a maternal
When a Canadian nephrologist of Ashkenazihaplogroup.
parentage attended synagogue one morning, heEither Y-DNA or mtDNA test results can be
noticed that a Sephardic congregant with thecompared to the results of others via private or
same surname as his – Cohenpublic DNA databases.
— seemed to have completely differentBiogeographical and ethnic origins
physical features. According to the traditions ofAdditional DNA tests exist for determining
Judaism, Cohens are descended from the samebiogeographical and ethnic origin, but these tests
male ancestor, the priest Aaron, brother ofhave less relevance for traditional genealogy.
Moses. Dr. Skorecki reasoned that if KohanimSee biogeographic ancestry, genealogical DNA test
(plural of Cohen) were indeed the descendants ofand population genetics (the study of the
only one man, they should have a common set ofdistribution of and change in allele frequencies).
genetic markers and should perhaps preserveHuman migration
some family resemblance to each other.Genealogical DNA testing methods are also being
To test that hypothesis, he contacted Professorused on a longer time scale to trace human
Michael Hammer of the University of Arizona, amigratory patterns and determine, for example,
researcher in molecular genetics and pioneer in Ywhen the first humans came to North America
chromosome research. Their report in the Natureand how they got there. For several years, a
in 1997 sent shock waves through the worlds ofnumber of researchers and laboratories from
science and religion. A particular marker patternaround the world have been sampling indigenous
(now known as the Cohen Modal Haplotype, orpopulations from around the globe in an effort to
CMH) did indeed appear in 98.5% of Jewish menmap historical human migration patterns. Recently,
bearing the surname Cohen (or a variation thereofseveral projects have been created that are
such as Cone). It was apparently true thataimed at bringing this science to the public. One
knowledge of their priestly calling and descentexample is the Genographic Project, which aims
from the Biblical Aaron had been strictlyto map historical human migration patterns by
preserved for thousands of years. Moreover, thecollecting and analyzing DNA samples from over
data showed that there were very few100,000 people across five continents.
“non-paternity events."Typical customers and interest groups
The first to test the new methodology in generalMale DNA testing customers most often start
surname research was Bryan Sykes, a molecularwith a Y chromosome test to determine their
biologist at Oxford University. His study of thefather's paternal ancestry. Females generally begin
Sykes surname obtained valid results by lookingwith a mitochondrial test to trace their ancient
at only four markers on the male chromosome. Itmaternal lineage, which males often have tested
pointed the way to genetics becoming a valuablefor the same purpose.
assistant in the service of genealogy and history.A common consumer goal in purchasing DNA
In 2001, Sykes went on to write the populartesting services is to acquire quantified,
book The Seven Daughters of Eve.‘scientific’ linkage to a specific
In the wake of that book's success, and theancestral group. A compelling example of this
growing availability and affordability of genealogicalmotive is found in the expressed desires of some
DNA tests, genetic genealogy as a field beganconsumers to be proven to have Viking paternal
growing rapidly. By 2003, the field of DNA testingancestry. In keeping with this marketplace
of surnames was declared officially to havedemand, one British DNA testing service, Oxford
“arrived” in an article byAncestors, offers a Y chromosome test
Jobling and Tyler-Smith in Nature Reviewspurporting to measure whether given males are
Genetics. The number of firms offering tests, andof "Viking stock." Those whose DNA falls into the
the number of consumers ordering them, haddesignated haplogroup are issued Viking
risen dramatically.Descendant certificates by the testing service.
Another milestone in the acceptance of geneticThe same DNA testing company (Oxford
genealogy is the Genographic Project. TheAncestors) participated in producing a televised
Genographic Project is a five-year researchdocumentary, "The Blood of the Vikings," in
partnership launched by the National Geographicconjunction with the BBC, which showed how
Society and IBM in 2005. Although its goals areDNA testing could reveal Viking ancestry.
primarily anthropological, not genealogical, theThe Rootsweb DNA-Genealogy Internet
project's sale of over 150,000 testing kits (as ofdiscussion group has a membership of 750
July 2006) of its public participation kits, which testsubscribers from around the world. Some
the general public for either twelve STR markerssubscribers have had various DNA tests
on the Y chromosome or the HVR1 region of theperformed and are seeking advice and guidance in
mtDNA, has helped increase the visibility ofinterpreting their results, and the list also includes
genetic genealogy.administrators of DNA projects that examine
Annual sales of genetic genealogical tests for allsurnames (e.g., Stewart, Hurst, Wells, etc.),
companies, including the laboratories that supportgeographic regionans (e.g., the Shetland Islands,
them, are estimated to be in the area of $60Mexico, Scotland, etc.), or ethnic groups (e.g., the
million (2006).Pennsylvania Deutsch, African Americans, etc.).
UsesThe sophistication of subscribers ranges from
Paternal and maternal lineagesexpert to novice, and, in some cases, subscribers
The two most common types of genetichave been credited with making useful and novel
genealogy tests are Y-DNA (paternal line) andcontributions to knowledge in the field of genetic
mtDNA (maternal line) genealogical DNA tests.genealogy.
These tests involve the comparison of certain