DNA Spotlight: The Shared cM Project

DNA Spotlight: The Shared cM Project

April 09, 2019

When you get your DNA results, the DNA company tries to give you a sense of how you are connected to your matches. They will identify each relationship as parent, close family, sibling, second cousin, third cousin, fourth cousin, distant cousin, etc.
On MyHeritage it looks like this:


On Ancestry it looks like this:

It's important to understand that the relationship provided is just an estimate. There are actually a number of possible ways you could be related to any given DNA match.
Now take a look at those same images and notice that next to or underneath the relationship you see a number and the initials cM. cM stands for centiMorgans which is the unit of measurement for DNA. The more cM you share with a DNA match the more closely related you are. The less cM you share, the more distant your relationship.
The Shared cM Project
In order to understand better all the possible relationships you have with a DNA match, genetic genealogist Blaine Bettinger came up with a data driven tool called the Shared cM Project. Blaine asked DNA test takers to provide the amount of cM they shared with known relationships. From this he was able to create charts that showed the various possible relationships through the range and averages of centiMorgans.
From the data, Blaine produced the Shared cM Project chart below. In each box the first line is the relationship, the second line is the average cM for that relationship and the third line is the range he has determined based on the data.
So if we take the example above - 2nd-3rd cousin, 276 cM - we would look for the box where the average is closest to 276 cM. You'll notice that there are three boxes that are pretty close: Half 1C1R (226 cM), 1C2R (229 cM) and 2C (233 cM). If you look beyond the averages to the ranges you'll notice that there are even more possibilities. This is just to show that your actual relationship to your DNA match could be any of a number of possibilities besides what the DNA company estimates for you. In this particular case, I know the cousin personally and I am accurately able to identify her as my second cousin and not a third cousin or any of the other choices.

Blaine Bettinger, The Shared cM Project, https://thegeneticgenealogist.com
(Click to enlarge), Creative Commons attribution

Interactive Shared cM Project on DNA Painter
Recently Jonny Perl, the creator of DNA Painter presented a webinar about DNA Painter on Legacy Family Tree Webinars (which is free to watch). Jonny has transformed Blaine's chart into an interactive tool on DNA Painter.
Let's see how it works with two new DNA matches I received just today.
From the main DNA Painter home page choose the Tools menu option.

On the next page choose the Shared CM Tool option:
Next put the amount of cM your share with your DNA in the Filter box.
For this exercise I will use my two brand new dna matches.


For the first new cousin I get this result:
You can see there are a lot of possibilities for this relationship! In fact, this cousin I know personally. She and I are Half first cousins once removed (Half 1C1R). That result was in the second tier of options. It's important not to make assumptions when working with unknown matches.
The second new match of the day was also described as a 3rd-4th cousin.
It's interesting to see how much the results change just by changing the cM a bit. The results are quite different even though they were both presented in the same 3rd-4th cousin range. This person is unknown to me. I will have to compare our shared matches and do some research to determine which of the above relationships is accurate. It's intriguing and I can't wait to uncover this new cousin.
Both the Shared cM Project chart and DNA Painter are free to use.  These tools will greatly help you in your genetic genealogy research. Give them a try.
You can learn more about understanding your DNA results from classes in the Legacy library. If you are just starting out with DNA take a look at Blaine Bettinger's Foundations of DNA series. If you're already pretty comfortable with DNA then choose from among the 74 DNA classes in the library.

Marian Pierre-Louis is the Online Education Producer for Legacy Family Tree Webinars. She hosts the monthly evening webinar on the second Tuesday of each month.  Her areas of expertise include house history research and southern New England research. Check out her webinars in the Legacy library.

Ancestry.com Sued for ‘Misleading’ Customers About DNA Data

Dick Eastman · April 26, 2019 · DNA, Legal Affairs · No Comments

Genealogy information provider Ancestry.com has a “longstanding practice” of failing to get sufficient informed consent agreements from customers who submit medical and DNA information, a new lawsuit alleges.
Lori Collett sued the Utah-based company’s subsidiaries—Ancestry.com DNA LLC and Ancestry.com Inc.—for allegedly “misleading and deceiving patients in California and across the country about what Ancestry was actually doing with their DNA.”
Bloomberg news has a brief radio report about the lawsuit at http://bit.ly/2VAn7Gt.

New Online Tool Will Help Families Track Down Scottish Ancestors

Dick Eastman · March 28, 2019 · Online Sites · 3 Comments

The Scottish Emigration Database lists details including the town or village of origin, address, destination and occupation, as well as information about specific vessels and shipping lines. The free online tool contains the records of 21,000 people.
The main search focuses on people – you can filter based on name, occupation, gender and address. You can even search by destination port. The database also allows people to search by ship name – so if you know which ship your ancestors sailed on, but don’t know a great detail about them, this might help.

The online database allows you to search thousands of entries using as much, or as little detail as you have – a detailed user guide is available here.

You can learn more at: http://bit.ly/2uuoffz.

Is DNA Evidence Reliable?

Dick Eastman · March 26, 2019 · DNA, Legal Affairs · 2 Comments

DNA has become a major tool for use by police in solving cold cases of murder and other violent crimes. In the past year, about 50 cold cases have been solved nationwide using public genealogy websites. But is this evidence alone reliable?
James H. Manahan, J.D., has written an article in the Lake County (Minnesota) News-Chronicle that tells why DNA evidence alone can be misleading. Manahan cautions that DNA is a great tool but also must always be used in conjunction with old-fashioned police work.

Manahan describes a case when a homeless man was accused of murder, based upon DNA evidence from a 7-year-old cold case. Luckily, the man’s public defender found a subtle problem with the evidence. In short, the DNA evidence obtained was “identified” as coming from the wrong man. Instead of spending the rest of his life in jail, the homeless man was quickly cleared of the crime. Had the public defender not been suspicious, the outcome could have been far different.
The article quotes DNA and genealogy expert CeCe Moore. It also quotes the homeless man, Lukis Anderson, when he got out of jail: “There’s more that’s gotta be looked at than just the DNA. You’ve got to dig deeper. Reanalyze. Do everything all over again before you say, ‘This is what it is.’ Because it may not necessarily be so.”
You can read this interesting story at: http://bit.ly/2TWn6wi.