Maternal and Paternal haplogroups CAN tell us something about our ancestors, and possibly help place new matches. But there are serious limits.
The maternal haplogroup is entirely female inherited, so a match to YOUR maternal haplogroup can only tell you about your direct line of mother’s-mother’s-mother, and so on. Because it does not change with recombination, only occasional mutation, a maternal haplogroup match might mean your common many-great-grandmother is centuries in the past. Both males and females HAVE this, because it is actually mitochondrial DNA, so abbreviated mtDNA. However, is it often easier to call it maternal, as that is how it is inherited. Women give it to ALL of their children.
Likewise, paternal haplogroups are entirely male, and also don’t recombine, just mutate rarely. A shared paternal haplogroup could mean your most recent common many-great-grandfather is very long ago. Because both types of haplogroups are very stable, there are multitudes of people who will match in that way, but in no other way, for the relationship is so far distant, there is no longer any shared autosomal DNA. Here’s a good video from 23 & Me to help understand. Only men get Y-DNA from their fathers, but women can infer the paternal haplogroup for ourselves, based on testing from a close paternal relative. Testing my brother gave me that paternal haplogroup assignment.
However, you can use the NON-matching haplogroups of your direct matches to identify the haplogroups of selected ancestors, by examining your matches inheritance. Only some of your matches will be useful for this process. For example, I share DNA with a 3rd cousin, and her line of descent from our common great-great-grandmother is entirely female, while mine is broken by my father. But I can know that before the line was broken, my grandmother and great-grandmother also shared that same haplogroup. My 1C1R, who is a descendant in the entirely female line of my grandmother should also share that same haplogroup, and does. Thusly, I can label my great-great-grandmother MLR with U4a2a, as well as my grandmother, and great-grandmother. I add that information on DNApainter on the comments for the group of DNA assigned to each of those 3 women.
On the paternal haplogroup side, there is a 3C1R with completely male inheritance to my multi-great-grandfather on my father’s side. While my father is deceased, and never tested, my brother has tested, and those two entirely male inheritance trails have matching haplogroups. Again, I will label the groups on DNA painter of all my direct line paternal ancestors. For reference, I’ve also filled in a 5 generation chart with what I know right now. (chart courtesy of sample-templates123.com)
Now, I’m going to double check each one of the previously processed paternal matches, to look for other purely paternal or purely maternal lines of descent, to see if I can fill in any more of my chart.
So remember how mothers give mtDNA to all their children? I’ve got a male 2C1R match who has an entirely female line of inheritance before himself. I can add that haplogroup to my great-grandmother. She gives it to her son, my grandfather, but it doesn’t pass down from there. But her mother, my great-great-grandmother, also shares that haplogroup.
So with only 3 primary matches – my brother, my 3rd cousin, and my 2nd cousin, once removed; I’ve got at least one haplogroup assigned to 9 of 15 paternal ancestors. Going forward, I will update the chart as I process confirm additional matches. In reviewing the previously known matches, I found several additional matches that confirmed the haplogroups already assigned.
But how would you use haplogroups to help place matches, you ask? The first step assumes you have a fairly well painted chromosome map, and you have an idea of who could be the MRCA. If one their haplogroups match that MRCA, then you can zero in on the direction of their trail to that probable ancestor – either via their straight maternal, or straight paternal line. Remember, a male match can still use his straight maternal line.
In many cases, there will have been too many male-female switches in the inheritance trail to be useful. Also be cautious, there are so many living individuals within each particular haplogroup, that sharing the same group may not tell you anything about recent ancestry.
However, the haplogroups can sometimes tell you about ethnicity. That isn’t my expertise, so for further reading, I suggest Exploring Ethnicity with DNA pt 1.
Historical Pursuits 