What Is a Haplogroup? - Geneanet

Haplogroups are identified by a code (for example: “T”, “H5a1”, “E1b1a1a1”) which simplifies genealogical tracing of these genetic mutations.

In human genetics, the haplogroups most commonly studied are:

• The patrilineal line haplogroup (Y-chromosome), passed from father to son (women don’t have it) ;
• The matrilineal line haplogroup (mitochondrial DNA), passed from mother to offspring of both sexes.

You can look at lists identifying the origin of your haplogroups or famous “cousins” (some quite distant).

Going further…

The generally accepted theory today is that all humans descend from a common ancestor who lived somewhere in Africa, several hundreds of thousands of years ago. Thus, all men alive today have a common ancestor, called Y-chromosomal Adam or patrilineal most recent common ancestor (MRCA), and all women have a common ancestor, called Mitochondrial Eve or matrilineal MCRA.

With the passage of time, a series of mutations have modified the genome of the decendants of the male MRCA and female MRCA, resulting in human populations with increased diversity. These populations have dispersed around the world, spreading their DNA and mutations. Haplogroups define human groups having a common male or female ancestor, and having the same series of mutations on the Y-chromosome or in mitochondrial DNA; it is therefore possible to date and trace these migrations.

Haplogroups are useful in genetic genealogy since they provide complementary information to autosomal DNA (atDNA) analysis.

What is a Y-chromosome (patrilineal line) haplogroup?

The Y-chromosome is transmitted only from father to son (via the patrilineal line). Women don’t have a Y-chromosome and therefore do not have a Y chromosome haplogroup in their genome.

Over generations and since the Y-chromosomal Adam MRCA, mutations have altered the Y-chromosome. Comparing the mutations between two males tells us how closely they are related (this relationship may be tens of thousands of years old, or may be much more recent in time). The higher the number of common mutations on the Y-chromosome, the more precise the paternal haplogroup and the closer the common ancestor is in time. On the contrary, the fewer common mutations there are, the older the common ancestor will be, having lived tens of thousands of years ago.

In our European societies where a family name is traditionally transmitted from father to son, the history of the last name generally coincides with the history of the Y-chromosome of a lineage. Studying this correlation thus allows scientific confirmation of links (recent or not) between two men theoretically sharing the same agnatic (male) lineage.

The phylogenetic tree can be read in the same way as a family tree: the further back one goes in the tree, the older the haplogroups are. To give an order of magnitude, the characteristic mutations of haplogroup P would have appeared 40,000 to 45,000 years ago, those of haplogroup R around 25,000 years ago. For each new haplogroup, new mutations are added to the previous ones. In concrete terms, haplogroup R therefore groups together individuals with the characteristic mutations of haplogroup P, to which new mutations are added.