Genetic genealogy

Genetic genealogy is research into individuals' biological relationships and family history through the use of DNA tests and written documents. Genetic genealogy is primarily based on comparing DNA tests on individuals who have had their DNA tested. By comparing tests, one can, for example, determine the closeness of kinship or the distance to the most common recent ancestor in relation to those tested.

A Part of the Field of Genealogy

The number of people practicing genetic genealogy has increased significantly in recent years and Finland also has tens of thousands using its methods. DNA tests have become a part of the field of genealogy and genetic genealogy is not seen as something apart from all other genealogy, but rather DNA tests have become a new tool for all genealogists. Genetic genealogy is not separate from documentary sources or traditional genealogy but offers a new research method alongside traditional documentary practices.

DNA Tests Used in Genealogy

The DNA test kits used in genealogy are generally direct-to-consumer test kits that are ordered directly from independent companies making them. The tests are divided into autosomal tests (cousin test), paternal lineage Y-DNA tests and maternal lineage mtDNA tests. All tests are based on comparing the tested to other tested people but the tests utilize different parts of the human genome.

Autosomal or cousin tests are by far the most common type of test and their uses in genealogy are the most varied. In the autosomal test a person's inheritance of autosomes (i.e. 22 pairs of chromosomes, not including sex chromosomes) inherited from both the mother and father is compared to others who have done the same company's DNA kit test. The other people tested make up lists of matches where one can compare the amount of shared common inheritance and by that can determine the closeness of kinship. Genetic cousin tests can be done by both men and women. These tests are especially useful as an aid to traditional genealogy in e.g. verifying family origins, finding out the paternity of a child born out of wedlock or in researching gaps found in other documentation.

Paternal Y-DNA tests, on the other hand, are based on the mapping of the Y-chromosome inherited from father to son, and the tests can be used, for example, to map the kinship of people with the same surname, to verify surname changes, to find out the father's sons born out of wedlock or to trace the settlement history of direct male lines. Y-DNA tests can only be done on men but women can still test their father, brother or cousin if they are interested in their own paternal lineage.

Matrilineal mtDNA tests map mitochondrial DNA that is inherited from the mother to her children i.e. direct maternal lines. mtDNA tests can be done by both men and women but mtDNA is always inherited from the mother to her children. The main usages of mtDNA tests are e.g. in finding out settlement histories or in tracking the mother's family of an adopted child.

Especially the Y-DNA and mtDNA tests form their own category of researcher - one that is interested more widely in population history and the migrations of direct patrilineal and matrilineal lines during history. These tests in a way let you go beyond documentation since even though the tests can't reveal names, the direct patrilineal and matrilineal tests do still reveal the movements of these direct individual family lines and their relationships to other lines all the way back into murky prehistoric times.

Genetic inheritance explained with gummy bears.

The Human Family Tree

In population history and population genetics direct paternal and maternal lines can be described by so called haplogroups. Population genetics research has grouped the human population into two haplotrees and both have numerous subgroups. The grouping has been done separately for the Y-chromosome DNA and for mitochondrial DNA. The haplogroup is an individual's precisely defined place in the person's patrilineal or matrilineal family tree. Depending on the DNA test or mapping the haplogroup can be defined very precisely, at its best to such a small branch that it won't have more than a couple people on it. Research of haplogroups and the human family tree is analogous to the ancestry research of traditional genealogy.

Genomic Information in Genealogy

Information on a person's inheritance, i.e. genomic information, can be used in genealogy in many different ways. The information is always sourced from one single individual using a DNA test kit. The test does a DNA mapping and comparison which is then compared with other people tested. The results of mapping and comparing can find distant cousins and define haplogroups. Genetic genealogy can be a useful tool for traditional genealogy in verifying kinship and in proving information found in documentary sources.

For example by comparing test results from Y-chromosomal DNA one can confirm or rule out the kinship of two male lineages. This can be used to help in finding out the relationship between two family branches or to identify the father of a son born out of wedlock. The identity of the father of a son born out of wedlock can usually be found with an autosomal or cousin test which compares the amount of common inheritance between two individuals. The more common inheritance they share, the closer the family relationship is. In these examples, genetic genealogy does not replace the need for traditional genealogy.

DNA Test Service Providers

DNA test kits usually use a cheek swab sample or a saliva sample. There are currently about 200-300 internationally well-regarded companies that offer various kinds of DNA tests. Since tests are based on comparisons among those tested, it is suggested that you order a test kit from a company that has a large user base. The four biggest companies have globally over ten million customers. The biggest portion of all DNA tests in the world are done for genetic genealogy research.

Below are listed the world's four biggest providers of DNA test kits. Finns have mostly used MyHeritage or FamilyTreeDNA. Americans, on the other hand, have often used Ancestry and many Americans have roots in Europe because of European emigrants. Before taking your own sample and ordering a test kit it is advised to inform yourself of the different tests by different manufacturers.

Data Protection

Before ordering a DNA test kit you should think about data protection issues and choose the service provider to whom you will send your sample to be analyzed. You should familiarize yourself with the terms and conditions of the service providers and understand that the income model of some test companies include other activities than just selling tests to consumers.

A DNA test is just as unique as a fingerprint and anonymizing genomic information is not a simple task. Tests not only provide information about the test subject but also about their relatives. Usually tests done for genealogical reasons don't examine the entire genome but only the relevant parts for the study. It is good to remember that you do not have to reveal your family tree to the service provider and, if you so wish, you can hide your own results on the service provider's database.


  • P. T. Kuusiluoma (toim.): Johdatus geneettiseen sukututkimukseen. Suomen Sukututkimusseuran oppaita 4. Helsinki: Suomen Sukututkimusseura 2017. 
  • Bettinger, Blaine T.: The Family Tree Guide to DNA Testing and Genetic Genealogy. Family Tree Books 2016.
  • Peter Sjölund: Släktforska med DNA. Sveriges Släktforskarförbunds handböcker 9. Stockholm: Sveriges Släktforskarförbund 2015.