If you’re doing DNA tests for family history, you may see lots of predicted cousin matches: 2nd, 3rd, 4th, etc…..But what does that predicted genetic relationship actually mean? Learn about centimorgans, the powerful genetic genealogy unit of measure, and how it helps your research.
How DNA Tests Measure Genetic Relationships
When we are looking at genetic relationships, there are also many ways we can measure them. But ultimately, we want the testing company to tell us how likely it is that a particular individual shares a single, recent common ancestor with us. One factor in this calculation is to take into account the total amount of DNA we share with that match.
Currently, all the testing companies are reporting this sum in centimorgans (cMs). Every company reports to you the total number of shared cMs, as outlined below.
AncestryDNA: Click on the match to access the personal profile page for that match. In the second section, under Predicted Relationship, you will see the confidence level. To the right of the confidence level, you will see a grey circle with a little “i” in it. Clicking there will show you the total amount of shared cMs as well as how many pieces of DNA you share.
Family Tree DNA: On the main match page for your Family Finder results, you will see the total amount of shared cMs in the third column.
23andMe: You can see the percentage of shared DNA from the main DNA Relatives home page. To convert the percentage into centimorgans, just multiply your percentage by 68 (that will at least get you close). You can also see total shared cMs in the chromosome browser tool (go to Tools > DNA Relatives > DNA).
MyHeritageDNA: The total amount of shared DNA is shown on the main match page under the title Match Quality. MyHeritage also has a new DNA Match Review page. Click here to read more about that.
Centimorgan: A Genetic “Crystal Ball”
It is very tempting to think of a cM just like you would think of an inch or a centimeter, and for all practical purposes, that is okay. But it is actually much more complicated than that.
A cM is actually more like a crystal ball: it helps us predict how likely a piece of DNA looks exactly as it did a generation ago. This, in turn, helps us calculate how far back we should be looking for the common ancestor between two people.
But for our practical purposes, you can use the total amount of shared DNA, in combination with this chart compiled by Blaine Bettinger and the Shared cM Project, to better assess your genealogical relationship with your match based on your genetics.
To use the chart, take the total amount of shared DNA you have with a match, and look up that number in the chart to get an idea of what kind of genealogical relationship might best fit the genetics that you see. For example, if I share 69 cM with my match, we might be third cousins. But we might also be second cousins once or twice removed.
How do you figure out which one? Simply put: do genealogy research! It’s time to use traditional records and research skills to better understand the genetic clues in your family history mysteries.
My series of DNA quick reference guides can help you get the most out of your DNA tests for family history. I definitely recommend the value-priced bundle of all 10 guides. But I especially recommend the guides listed below if you’re to the point where you’re trying to understand what genetic relationships mean:
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The key to learning about our ancestors from our own DNA is to have a lot of people tested who can all trace their ancestry to a specific geographic location. A groundbreaking scientific study has just been published in Nature by Stephen Leslie and colleagues that details the origins of the people of the UK. (Read the abstract here.)This study has ramifications for you, as a genetic genealogist, even if you don’t have origins in the UK.
Dr. Leslie and colleagues collected data from 2,039 Britons of European ancestry who lived in rural areas and knew that their four grandparents were all born within 80 kilometers (50 miles) of each other. This means that their DNA should accurately represent the DNA of individuals living in that area in the late 1800s. Using multiple fancy and advanced statistical methods, the researchers identified 17 distinct genetic groups. When they overlaid these groups on a map of the UK, what they found was remarkable. Each genetic group, with few exceptions, mapped to a very specific geographic location.
The largest cluster by far, encompassing half of those tested, maps to Central/South England. Well, the first serious settlers of Britain were from the Roman Empire whose influence in 43 AD at the time of their entry into Britain was extensive, from Spain to France to Italy to parts of the middle east and North Africa. Then around 450 AD the Angles, from modern day northern Germany and southern Denmark, and the Saxons, from Germany, invaded. According to linguistic and archeological evidence, the previous Roman culture was basically wiped out. But were the actual people destroyed, or just their culture?
To find out, the team compared the UK samples with 6,209 people from continental Europe to understand their ancestors’ contributions to Britons’ ancestry. According to the DNA evidence, the descendants of those first Roman settlers are still very much alive. In fact, the paper reports that Saxon ancestry in Central/South England is very likely to be under 50%, and most likely in the range of 10–40%, with instead a large portion of the genetics now being attributed to France and by extension, the Roman Empire.
Another interesting finding: the Viking conquerors were nearly genetically absent in most of the UK.
Very unfortunately, this data on DNA in the UK will not be a part of the reference samples at your genetic genealogy testing company. But it does demonstrate unequivocally that THIS WORKS! DNA testing can help us trace our ancestral origins and thanks to improved techniques and larger data sets, we have much to look forward to. Dr. Peter Donnelly, population geneticist at Oxford and co-author of this paper said, “History is written by the winners, and archaeology studies the burials of wealthy people. But genetic evidence is interesting because it complements that by showing what is happening to the masses rather than the elite.”
From Diahan Southard, Your DNA Guide here at Genealogy Gems: DNA testing is one of the most personal ways to get involved in your family history. You have DNA from your parents, who have DNA from their parents, and so it goes, back into your greats and great-greats. The technology of genetic genealogy is all about tapping into that DNA record and pulling out information that might be useful in your family history. DNA can do this for you in two ways:
First, it connects you to places. These are places where your ancestors came from a hundred, a thousand, or tens of thousands of years ago.
Second, it connects you to people. These people are your genetic cousins, other living people who have taken the same DNA test that you took. The similarities in your DNA tell you that you share a common ancestor. You can then examine the pedigree of your match and work with them to help verify your family history, or give you new ideas about who your ancestors might be.
Types of DNA Tests for Family History
You have three choices of DNA tests, each with its own unique purpose.
YDNA – Essentially, if you want to know about a male ancestor, you need to find a direct male descendant to be tested. So if I want to know about my 3X great grandfather Morris Mitchell, I need to find Morris’s son’s son’s son, etc. until I find a living male with the Mitchell surname who can be tested on the Y chromosome DNA (mtDNA) test at Family Tree DNA.
mtDNA – If I want to know about a female ancestor, let’s say Mary West, I need to find Mary’s daughter’s daughter’s daughter’s etc. child (male or female) to take the mitochondrial DNA (mtDNA) from Family Tree DNA.
Autosomal DNA – For any ancestor, male or female, who is fewer than 5 generations from you, you can take the autosomal DNA test at either Family Tree DNA, AncestryDNA, 23andMe, or MyHeritage to find out more about that individual. Remember with the autosomal DNA that you always want to test the oldest generation first. So anyone who does not have both of their parents living should take the autosomal DNA test.
Companies that can Test DNA for Family History
There are several companies that test DNA for family history including:
Each of these companies is offering a very similar kind of test, but each has their own unique tools and databases. Decide which company you want to test with by evaluating things like:
their website accessibility
their company goals
and especially the size of their database
You can see a table comparing these companies here. The MyHeritage test is new, and is not on the chart yet, but will be soon.
Great (DNA) Expectations
The best thing you can do when setting out on your genetic genealogy journey is set good expectations. You can expect that the test will document the personal genetics of the person who takes it. By so doing, you are creating another genealogy record that will last for generations. This test will link you to your ancestors via your cousins. That means that you may take the test looking for ancestors, but what you get are cousins. It will take traditional genealogy work to turn those cousin connections into ancestral connections. Above buy prescription medicine overseas all, expect that this is a growing industry, and what we know today is different than what we will know tomorrow, so enjoy the journey!
DNA Resources
There are several comprehensive books on Genetic Genealogy out there. However, for the layman who just wants to understand their DNA test results and get some additional value from them, an entire book full of scientific explanations can be overwhelming and daunting. The following email is one we receive regularly:
Could you direct me to an understandable publication which explains dna results in layman’ terms ?
Thank you
Anne B.
Genetic Genealogy for the Layman
From Lisa Louise Cooke, host of The Genealogy Gems Podcast: I put myself in the category of “layman” when it comes to understanding DNA test results. And that’s why when I met DNA expert Diahan Southard at a genealogy conference, I immediately invited her to join Genealogy Gems. Diahan’s enthusiasm is contagious, and her ability to explain genetic genealogy to the layman is second to none!
I encouraged Diahan to immediately get to work putting her easy-to-follow explanations into a new series of quick reference guides. Genealogy Gems Publications is proud to publish her wonderful series of DNA quick reference guides for understanding your DNA results in plain language, and helping you get the most out of the investment you made in testing.
Start Here to Jump into Using DNA for Genealogy
Here’s a link to our DNA videos on YouTube with the author of the guides, Diahan Southard. As you will see, she has a ton of enthusiasm for helping the layman understand and get the most out of their DNA!
Diahan has a regular segment on my free Genealogy Gems Podcast where she answers your questions and provides invaluable insights into the latest in genetic genealogy. You can also find the complete archive of DNA articles at Genealogy Gems by clicking here. The most recent will appear first and then scroll down to read through the past articles.
For those who have tested with Ancestry DNA
If you took the Ancestry test, I would definitely recommend the following guides:
The beauty of the DNA quick reference guide series is that you can mix and match the guides to perfectly suit the testing you have done. We’ve published Diahan’s guides that delve into the testing companies FamilyTreeDNA and 23andMe, as well as the other tests available such as Mitochondrial (for your maternal line – both men and women can take this test) and YDNA (for your paternal line – only men take this test.)
Take Your DNA Test Results to the Next Level
If you’ve already tested and feel like you have a good foundation, then I highly recommend Diahan’s Advanced DNA Bundle. It will take your DNA test results to the next level by instructing you on the heart of what matters in plain English.
DNA in the News
As of March 28, 2017, AncestryDNA customers can see if their ancestors belonged to about 300 different Genetic Communities, small migratory groups that can be identified by DNA. In the next free Genealogy Gems podcast episode #202, you will learn more about it straight from Ancestry’s Chief Scientific Officer, Catherine Ball. For more information on Genetic Communities, watch the video below:
New and updated records for Canada and the United States are hot off the press this week. Mortality schedules, cemetery records, Roman Catholic records, and passenger lists are listed for Canadian genealogy research. For the United States, check out Ohio newspapers, New Jersey census records, Confederate maps, and more.
Canada – New and Updated Collections
Ancestry has three brand new collections of Canadian records. First is the Census Mortality Schedule, 1871, covering the provinces of New Brunswick, Nova Scotia, Ontario, and Quebec.
Specifically for Ontario, Toronto Trust Cemeteries, 1826-1989 includes records of several Toronto Cemeteries. And the Roman Catholic Baptisms, Marriages, and Burials, 1760-1923 collection includes indexed records of Ontario baptisms, marriages, and burials. Other records, such as family lists, communions, and confirmations may appear, but do not have associated indices.
At FamilySearch, the collection of Canada Passenger Lists (1881-1922) has been updated with over 33,000 new indexed records. The collection contains an index and images of ships’ passenger lists (also known as ships’ manifests or seaport records of entry).
United States – Newspapers, Census Records, & More
Ohio. MyHeritage has a new collection of Ohio Newspapers from 1793-2009 that you’ll definitely want to explore. These newspapers come from various cities and towns throughout the state and may provide vital records substitutes as well as a glimpse of daily life.
New Jersey. State Census records for New Jersey are now online at Ancestry for the following years: 1855, 1865, 1875, 1885, 1905, and 1915. Records did not survive from all New Jersey counties but all available records are included in this collection.
Illinois. New over at FamilySearch are Illinois Mortality Schedules, 1850-1880. This collection lists people who died in the year preceding each census starting in 1850.
National Archives. Over 100 Confederate maps have been digitized at the National Archives. These maps are part of Record Group (RG) 109 and can be viewed online as well as downloaded. Additionally, some of the maps contained unique information on the back, and both sides are available to view in the Catalog.
Railroads. Finally, the Railroad Retirement Pension Index, 1934-1987 is available now at Ancestry. Records vary, but the information found may include birth date, death date, and social security number.
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Australian genealogy records are featured this week in new and updated collections online. Findmypast has two sets of records for Queensland and at FamilySearch, you can explore a big update to their free collection of immigrants ship papers. Also featured this week...