What’s a CentiMorgan, Anyway? How DNA Tests for Family History Measure Genetic Relationships
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:
- A Guide to AncestryDNA
- A Guide to Family Finder at Family Tree DNA
- A Guide to 23andMe DNA
- Breaking Down Brick Walls with DNA
- Organizing Your DNA Matches
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How to Identify Old Cars in Photographs
Follow these tips to identify old cars in photographs from your family albums. You can often identify the make and model of the automobile; decipher and date the license plates, and even discover additional documents relating to the earliest drivers on your family tree.
A listener’s mystery photo question
Many of us have mystery photos in our family archives. Jennifer sent me a creative question about identifying hers:
“Have you ever come across any information on searching old license plate tag numbers to find an identity of the registrant? I have old photos that, according to my aunt, are the family of my grandmother’s boyfriend, Max, before [she married] my grandfather. The photos are amazing. Very ‘Great Gatsby-esque.’ Amazing clothes and car, right?! One photo has a smiling man standing in front of an old car with a portion of the license plate showing. I do not know the identity of this man or children. I’m thinking start with searches for plates beginning with 109 in the years before my grandmother was married in the state of Indiana, where she and Max lived.”I didn’t know if I had a ‘lead’ in that or not. I may be pulling at strings. I’d love your advice.”
What a great idea! I haven’t tried Jennifer’s exact approach to researching license plates as a way of identifying owners. But I have a similar story about researching an old car in my own family photo. My story, below, may help Jennifer and anyone else wanting to identify old cars in photographs. Keep reading for tips on researching the make and model of a car; deciphering the license plate to help date the photo and even on finding early drivers’ records. Owning a car was (and still is) a source of pride and excitement for many families, so it’s really worth taking a closer look at their cars in old pictures.
An old car photo in my own family
Here’s a photograph I love of my grandmother Alfreda as a teenager, beaming as she poses beside the newly purchased family automobile. In her diary, she divulges her excitement for the surprise she came home to after church:
Oct. 21, 1929 Sunday. “Went to Sunday school and when I got back there was our new car waiting for me. Willy’s Knight. I drove it all around, went and gave Evelyn a ride. Made Mama mad.”
This diary entry piques my interest. What year was this? Where did the car come from? What’s a “Willy’s Knight?” And if Mama got mad, who gave Alfreda the keys? I suspect Alfreda may have been a bit of a Daddy’s girl, but alas, this photo may not be able to reveal that family dynamic. However, the photo does contain important clues that has helped me answer at least a few of these questions.
1. Identify old cars in photographs
Before you start trying to identify an old vehicle in a family photo, it will help to know whether it’s categorized as a veteran, vintage, or classic car. What’s the difference? According to ItStillRuns.com:
“Veteran cars were manufactured before 1903, vintage cars were made between 1903 and 1933, and classic cars are considered to be vehicles manufactured from 1933 until fifteen years ago.”
With these categories in mind, visit websites that can help you identify old cars by providing descriptions and pictures of various makes and models. Two sites I suggest are Hubcap Café.com: Collector Car Resources and a Flickr group called Vintage Car Identification. (This second one is for the truly stumped because you can submit a photo that car enthusiasts from around the world could help you identify.)
I already knew from Grandma’s diary that the car in the above picture was a Willys Knight. But I wondered if I could nail down the make and model. I ran a few Google searches and found some fantastic websites.
Paul Young’s Willys Overland Knight Registry website had just what I was looking for. The site features dozens of photographs of all the different makes and models of Willys Knight automobiles in chronological order. So I scrolled down to the late 20’s and compared each photo to the photo of my great grandfather’s car. Bingo! The 1928 Willys Knight 70A Cabriolet Coupe America matched the car to a T. Everything from the convertible roof, the headlights, bumper, and side view mirrors all matched up.
From there I clicked on the Willys Knight History link, which led to not only a written history of Willys Knight but a chart of Willys Knight Specifications. A quick scroll down led me to the specs for Grandpas 1928 70A series car. I learned that great-grandpa’s car was introduced in August of 1927 for the starter price of $1,295. (Here’s a free online inflation calculator. Try plugging in 1927 and $1,295 to find out what the car would cost in today’s money.)
I also learned that the car was a 6-cylinder, as well as specs on the horsepower, the wheelbase, and even the range of serial numbers that the car would fall within. This website was jammed packed with everything you could ever want to know about the Willys Knight car. (If you’re interested in chatting with others about Willys Knight cars, you could also visit this site’s Facebook page.)
My book The Genealogist’s Google Toolbox—which is where you’ll find all the tips you need for doing these Google searches–has an entire chapter on finding videos on YouTube. A quick YouTube search on “Willys Knight 1928” brought up this short but cool video uploaded in 2014: “Take a ride in a 1928 Willys Knight made in, owned in and driven in Toledo, Ohio.”
2. Investigate old license plates
In Family Tree Magazine a few years ago, I read an article called “Motor Trends,” written by my friend Maureen Taylor. She said that said that by 1918 all states had adopted license and registration laws. It recommended that you look for a license plate in old photos. License plates often have a year on them and possibly even the owner’s initials.
Unfortunately, the license plate in my photo is so dark I couldn’t read it at all. My guess is that this is probably the situation in many cases when someone has a photo of a car. So here’s what I did to solve this problem:
- I opened a digital copy of the photo with the basic photograph editing software that came with my computer.
- I cropped the photo to just show the license plate and then zoomed in to make the image as large as possible.
- I increased the brightness of the photo and adjusted the contrast. Often when you play with these two features, adjusting first one and then the other, you’ll get pretty good results.
- The final touch was to apply an auto-sharpening tool which defined the image even more.
As you can see in the “before and after” images below, what once was a blob of darkness now read: 2L 67 24.
There was something printed under the license number, but I still couldn’t quite read it. It looked like CAL 29, which would make sense because they lived in California and the year they bought it was 1929. But I couldn’t be certain. So I ran a Google search for “old California license plates.”
Several websites proved interesting for learning more about old California license plates:
- “The Colorful History of California License Plates” in LA Magazine
- WorldLicensePlates,com
- California DMV license plate introduction
- California State Archives
For example, I learned that California has required license plates since 1905. In that year, there were over 17,000 registered vehicles in the state. I found a replica 1929 license plate that read “CAL 29” across the bottom of it. Just what I’d thought mine said! And thanks to WorldLicensePlates.com, I was even able to determine that the license plate in my black and white photo had a black background and orange lettering.
What about the license plate in Jennifer’s photo? Only a partial plate is visible, but it’s enough to compare to images of Indiana license plates at WorldLicensePlates.com:
Jennifer can take several important clues from this comparison:
- It quite a dark plate with very light numbers. Even though it’s a black and white photo, based on the contrast, I think the license probably doesn’t have orange in it. (Eliminate 1929, 1930, 1931, 1935)
- There is no dash between the first 3 numbers and the next set (eliminate 1929)
- The style is more of a Sans Serif font (we can eliminate 1929, and 1930)
- Indiana appears at the bottom (eliminate 1931, 1933, 1935)
From these clues, I’d say that the 1932 plate is certainly the closest match.
3. Find records relating to early drivers
California state statutes of 1901 authorized cities and counties to license bicycles, tricycles, automobile carriages, carts, and similar wheeled vehicles. Owners paid a $2 fee and were issued a circular tag. Later, tags were either octagonal or had scalloped edges.
So this got me curious. Could I access records associated with my great-grandfather’s license plate and automobile registration? Typically states move records of this age to their state archives. I started by Googling California State Archives. The Online Archives of California has a searchable database that includes the state archive holdings. The online catalog has motor vehicle records (61 volumes!) for the first several years they were issued (1905-1913).
A description in the online finding aid stated: “Motor Vehicle Records, 1913 transferred those functions from the Secretary of State’s office to the Department of Engineering.” There are actually two clues here: 1) the phrase “motor vehicle records” is what I likely want to use when searching for records, and 2) the office that likely kept the records for my time period (1929) was the Department of Engineering. A followup search using these search terms got 13 results. Unfortunately, none of these records included 1929, and an email inquiry to the State Archives wasn’t fruitful, either. But this showed me that driver registration records may exist.
So may other driving-related records. I did several searches in ArchiveGrid, an enormous online catalog for archival collections. No California motor vehicle registrations popped up. But I did find a collection of 1928 maps and guidebooks for the Automobile Club of Southern California, held at the Brigham Young University library in Provo, Utah. There was also a collection of thousands of images collected by the Automobile Club of Southern California (mostly in the 1920s and 1930s) at the Huntington Library in San Marino, CA.
If I really wanted to learn more about the early-1900s “sport” of automobile driving in California, I could spend some time with record collections such as those.
Does this discovery change the course of my family history? No. But it was a heck of a lot of fun to learn what I did about the oldest automobile I’m aware of my family owning. It’s exciting to discover these little gems: they connect me to the past in such an interesting way. Even better, it gave me something to share with my husband, Bill, who loves old cars!
Learn more!
Hear inspiring stories and learn hands-on, try-it-now strategies for discovering your family history in my free Genealogy Gems Podcast. There are more than 200 episodes to get your genealogy motor running, with a new episode published each month. You’ll find the latest news, try-it-now online search strategies and inspiring stories to keep you on the road to genealogy research success.
Here’s what you’ll hear in Genealogy Gems Premium Podcast 163
In the new Genealogy Gems Premium Podcast Episode 163, you’ll hear what’s happening with a trove of 160,000 pieces of undelivered mail dating back to the 1600s, an adoptee’s personal response to Premium Episode 162, and tips on finding U.S. Navy photos....Colonial Genealogy Records – New & Updated Record Collections
Colonial genealogy records are just the tip of the iceberg in this week’s new and updated genealogical collections. If your roots go back to the early days of the American colonies, you will want to get started in these unique colonial genealogy records. Additionally, some fantastic finds for the United Kingdom and Denmark are also available in this week’s gems.
United States and Canada – Transatlantic Migration
First things first: where and when did your early American family arrive in the New World? Findmypast has added a new collection titled United States, Transatlantic Migration. This collection offers more than 30,000 records shedding light on the lives of your migrating ancestors from England, Scotland, Ireland, the Netherlands, Germany, and France from as early as the 1500s to as recent as the 1900s. Some information you may be able to find include: birth countries, date of emigration, ages, occupations, and names of family members. Once you have found where your family settled, head on over to the next record set for founding families.
United States – Colonial Genealogy Records
Findmypast’s colonial genealogy records set titled United States, Early American Families is a one-of-a-kind collection. These records will help you learn even more about your ancestral ties to early founding families in America. Dive into 140 publications containing over 86,000 records. These records provide details regarding the early families and their descendants. You might even learn the birth or death year of your family’s brick wall ancestor!
A sister colonial genealogy records collection titled United States, Early American Vital Records will also be of interest to those searching the colonial American family. This collection is filled with over 14,000 vital records as early as the 1600s! You will be delighted with the many birth, marriage, and death registers, gravestone inscriptions, and wills you can find here.
United States – Connecticut – Town Vitals
The Barbour Collection of Connecticut Town records, also from Findmypast, contains over 18,000 vital record volumes pertaining to Connecticut towns. You will need to search these records by surname. If your ancestral surname is located, you will find a PDF image that may list the birth or death dates, names of family members, and other personal details of the Connecticut family.
United States – Colonial Williamsburg
The Colonial Williamsburg Education Resource Library has been made available to everyone with a thirst for learning. What better resource to learn about your colonial American family research than with the library’s more than 100 lesson plans, background texts, and primary source media.
You will need to create an account, but it is free. Even though the account sign-up page seems to be for educators only, it is for everyone! I made my own account and got pretty excited looking through the many videos available. My son, a big history buff, is going to love this! I am always looking for ways to get the kids interested in family history.
United Kingdom – Military
Over 1.1 million War Office records covering officers, nurses, and other ranks have been updated in the British Army Casualty Lists 1939-1945 collection this past week. These lists cover the individuals reported as killed in action, wounded, prisoner of war, missing, died of wounds, dangerously ill, and more.
This collection at Findmypast is fully searchable and offers transcripts and digital images of the original documents. Most lists will give the person’s name, rank, service number, regiment, and status. It may also provide the date of death if applicable.
Denmark – Census
FamilySearch.org is where to look for your Danish ancestors! The name index of the Denmark census taken in 1911 is available for free at FamilySearch or with your paid subscription at MyHeritage.
The Denmark census of 1911 was the thirteenth census for the country. Though the census includes the countries of Greenland, Faroe Islands, and the Danish West Indies, what you will find on FamilySearch is only those enumerations for Denmark. The census is divided into three sections: Copenhagen city, other cities, and rural areas.
This census is written in Danish of course, so you might need a little help with some translation. Pop on over to FamilySearch wiki here to find a helpful chart of key words in both Danish and English.
This census asks questions pertaining to names of household members, birth date and year, birth location, religion, occupation, your means of getting to work, and how long it takes to get to your location of work! Isn’t that interesting?!
More Gems on Colonial American Family Research
Looking for even more tips and tricks to researching the colonial American family? Try these Genealogy Gem favorites!
If you haven’t been enjoying The Genealogy Gems (free!) Podcast, try it out today! A podcast is like listening to a favorite radio show from your computer or mobile device. Get up-to-date with everything new and exciting in the world of genealogy, learn a new tech tip, and find inspiration in these wonderful podcast programs!
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