Tuesday, November 20, 2018

6 Myopic Genealogists at #RootsTech

In just a few years #RootsTech has quickly grown to be the “beast” of genealogy conferences serving clientele around the world both live in Salt Lake City and through streaming to the remote corners of the earth. With its mix of genealogy and technology, it was only a matter of time before it attracted the attention of the 6 visually challenged genealogists from mythical Indostan.

Each of them had documented his paternal ancestry back at least to his respective great-grandfather who was a member of the group immortalized by John Godfrey Saxe in his 19th century saga, “The Blind Men and the Elephant.” [i]

It was six men of Indostan
To learning much inclined,
Who went to see the Elephant
(Though all of them were blind),
That each by observation
Might satisfy his mind.

The First approached the Elephant,
And happening to fall
Against his broad and sturdy side,
At once began to bawl:
"God bless me! but the Elephant
Is very like a WALL!"

The Second, feeling of the tusk,
Cried, "Ho, what have we here,
So very round and smooth and sharp?
To me 'tis mighty clear
This wonder of an Elephant
Is very like a SPEAR!"

The Third approached the animal,
And happening to take
The squirming trunk within his hands,
Thus boldly up and spake:
"I see," quoth he, "the Elephant
Is very like a SNAKE!"

The Fourth reached out an eager hand,
And felt about the knee
"What most this wondrous beast is like
Is mighty plain," quoth he:
"'Tis clear enough the Elephant
Is very like a TREE!"

The Fifth, who chanced to touch the ear,
Said: "E'en the blindest man
Can tell what this resembles most;
Deny the fact who can,
This marvel of an Elephant
Is very like a FAN!"

The Sixth no sooner had begun
About the beast to grope,
Than seizing on the swinging tail
That fell within his scope,
"I see," quoth he, "the Elephant
Is very like a ROPE!"

And so these men of Indostan
Disputed loud and long,
Each in his own opinion
Exceeding stiff and strong,
Though each was partly in the right,
And all were in the wrong![ii]

Having inherited their ancestors’ lust for learning as well as poor eye sight, these present day citizens of Indostan decided to make the trek to Salt Lake City to experience #RootsTech first hand. As soon they arrived each began to tweet and blog to their colleagues back in Indostan. Those colleagues began to wonder if the six were reporting from the same event. Although all were reporting back with the label #RootsTech 2019 there seemed to be little commonality in the events that were being reported.

Here are selected summaries from the posts they sent home:

Reported the first, after we arrived in Salt Lake City over the weekend, we all hurried to the Family History Library early Monday morning to consult documents not available to us in Indostan. At midweek I was so engrossed in my findings that I could not tear myself away to go down the street with my colleagues to just talk about genealogy research. I remained in the Library to, “Just do it.”

The second wrote lengthy posts each day about the inspiration he received from the world class keynote celebrity speakers. He also reported on the large events that marked the opening and closing of the conference. He also managed to get into the rehearsal of the world renowned Choir at Temple Square which made him envied by many of his readers back in Indostan.

The third reported on the useful information he was learning in classes and the difficulty of selecting which among the three hundred plus offerings available on a rich smorgasbord of all imaginable genealogical topics would be the most useful for him to learn about to enrich his research and share with those back in Indostan.

The fourth spent the entire week in the Exhibit Hall chatting with several hundred vendors from around the world who offered goods and services to genealogists. He was able to have hands-on opportunities with many of the products. Many of the larger vendors even offered mini-classes in the form of demonstrations on a daily schedule right in their booths. And oh the swag that was being offered to take back home—some just to be picked up and some more valuable that was awarded in periodic drawings.

The fifth had planned ahead so he was able to be able to sign up for coveted seats in the workshops in computer labs where he could practice hands on use of the products and tools that were being described in these sessions.

The sixth was eager to learn everything he could about incorporating DNA into his research so he arranged his schedule in a different way. He attended every class he could squeeze in from the DNA track; visited the booths of all the vendors large and small that offered DNA testing and interpretation and discussed his progress, roadblocks and research goals with their staff. He quizzed them about product enhancements on the horizon.

As the six reassembled at the airport to fly home, a dispute broke out about the true nature of #RootsTech and about whom among them and benefited the most.
And so these men of Indostan
Disputed loud and long,
Each in his own opinion
Exceeding stiff and strong,
Though each was partly in the right,
And all were in the wrong![iii]

Come to #RootsTech 2019 and write the learning plan that is best for you.

[i] Illustrator unknown, “Blind men and an elephant”, From Charles Maurice Stebbins & Mary H. Coolidge, Golden Treasury Readers: Primer, American Book Co. (New York), p. 89. 1909.
[ii] John Godfrey Saxe, “The Blind Men and the Elephant.” http://www.constitution.org/col/blind_men.htm, viewed 1/14/2013.
[iii] Ibid.

Thursday, September 13, 2018

New ways to look at your old DNA test results

Two announcements yesterday each give many of us something new to look at with some of our old DNA results. Both AncestryDNA and MyHeritage made important blog posts:

Transfers to MyHeritage:

MyHeritage tweeted that the company can now accept additional raw data transfers. However, note that there may be a real advantage in doing it before December 1st: 
We're excited to announce that we now support the upload of 23andMe v5 and Living DNA data files! Upload your DNA data now to receive DNA Matches and ethnicity estimates on MyHeritage for free. Read more: ht.ly/VP5630lNlya
The 23andMe v5 chip is the one the company has been using since the summer of 2017. This new conversion ability of MyHeritage will allow me to transfer kits of several of my family members who tested at 23andMe in the last two years. Previously, these kits could only be compared with other non-23andMe kits in the separate Genesis database at GEDmatch. 

Note that other newer entries to the DNA testing arena such as Living DNA also use this same chip and can be uploaded to use the diagnostic tools and matching database of MyHeritage that have become increasingly useful in the past year.

"Ancestry Unveils More Detailed and Precise Ethnicity Estimates"

The long anticipated update of the ethnicity estimates, at least for US customers were rolled out yesterday. This will give those of us who have tested at Ancestry something to ponder about. Chief Scientific officer Dr. Catherine Ball blogged:

Today, we announce that Ancestry will deliver ethnicity estimates with increased precision to its customers, through a new algorithm that analyzes longer segments of genetic information, marking an important evolution in the way we interpret DNA data. Having built and expanded our DNA reference panel, we have a better understanding of genetic signatures globally, can break down geographic ethnicity estimates with greater specificity and give you a more detailed picture of your origins.
Whether or not you agree that your new estimates more accurately describe your family's migration, they will give us much to discuss. Below is a summary of changes for my own estimates:

However, this summary does not tell me that some previous ethnicities dropped off completely in this upgrade. For me these were Caucasus 4%, Africa North 2% and Native American 1%. In neither version did Ancestry pick up on my known Finish ancestry which MyHeritage pegged at 2%. Sweden and Norway have not been called out in any of my other tests  They At least this gives me things to ponder.

What do you think about your new results?

Monday, June 18, 2018

Changes for RootsTech 2019

If you were at RootsTech 2018 earlier this year, you may have been put off by the long lines at Registration that snaked back and forth around the main hall of the Salt Palace. Lines also clogged the halls outside popular class venues as monitors had everyone line up to have their badges scanned before we could go inside and claim a seat. Even if you had been in the room for the previous presentation, you had to go out in the hall, get in line and get your badge scanned before you could come back in and claim a seat. As you might imagine criticism was sever and the planners of RootsTech 2019 listened.

On their behalf Dani-Tyler-Stahle has just released the following information:
We're excited to announce a few changes to the conference to help make the attendee experience even better. One of the biggest things we're doing is trying to eliminate lines! To address the line issues we saw last year, we are moving the check-in area to a larger space, we're not doing badge scanning, and logistically we are creating larger classrooms. Please share this piece on your channels and with your audiences. We read every piece of feedback we get from our surveys and these changes are a result of that.
Lets hope these changes make next year's conference more enjoyable for all attendees.

Saturday, May 5, 2018

Haplogroup Soup

Later this month in Burbank I am giving a presentation that I entitled "Using yDNA and mtDNA to Trace Deep Ethnicity". My thoughts about this have evolved since I submitted the proposal last year. As some of you know proposals for presentations at conferences like Genetic Genealogy 2018 must be submitted many months in advance. Even the syllabi for the chosen talks must be provided about four months in advance so that they can be compiled for distribution to registrants. This may be a fine timeline for presentations about 1890 US Census substitutes. However, it is really a challenge for cutting edge topics in genetic genealogy. So much can change during the gestation period of the conference program.

Such is the case with my thoughts about this particular talk. Now as I put the semifinal touches on my presentation, it occurs to me that I should have entitled my presentation "Haplogroup Soup".

Market research tells us that the majority of those who take atDNA tests, at least in certain demographics, do so because they are curious about their ethnic origins. To lure in new customers, testers are offered a chance to find out whether they should wear lederhosen or kilts to the next family gathering. Many of these customers know little about -- and sometimes care little about -- their family histories in the sense that us dyed in the wool genealogists think is appropriate. However, if they test we may find out that they are cousins previously unknown to us.

These autosomal DNA (atDNA) tests are clearly what is driving today's market for DNA testing. Our autosomes make up about 95% of our DNA. This is the only DNA test Ancestry.com has offered for almost a decade. It is the only part of our DNA reported by MyHeritage, Living DNA and 23andMe for ancestry information. 

I also will be presenting "Can DNA Tests Help ME Breakdown MY Genealogical Brick Walls?" a couple of days later at Jamboree. During that presentation I will go into more detail about your 4 different kinds of DNA and how each can help you learn about some of your elusive ancestors. But that is another topic for another day.

Meanwhile back to ethnicity testing. As I am sure most of you have heard, ethnicity predictions based on atDNA testing are just that -- PREDICTIONS. Even full siblings will often get noticeably different percentages on the same test. They should because siblings inherit different amounts and different segments of their atDNA from each of their 4 grandparents. Other factors also contribute to variances in ethnic predictions. Even when these are allowed for such ethnic projections are only accurate for a few generations back in time.

The Genetic Stew that is You

To map the trail our genomes have traveled through prehistory and into the early days of genealogical times, we must examine other parts of our DNA -- yDNA and mtDNA. Family Tree DNA (FTDNA) is the only major US company testing these parts of our DNA at levels that are genealogically useful for family historians. Your mtDNA and yDNA, if you are a male, only examine your exact matrilineal or your patrilineal lines. These results project back to and through many millennia of prehistory to allow your to follow the path your genome followed to get to the present. In my presentation I will discuss how you can use your own results, those of close relatives who test as your surrogates and tests of others with whom you can connect by documented paper trails to learn about the soup made up of the variety of haplogroups that make up the genetic stew that is you. 

Hope to see you in Burbank!

Sunday, April 15, 2018

Autosomal match through 6th Great-grandparents

We generally think that autosomal DNA (atDNA) is only reliable in evaluating matches back 3 to 5 generations. However, like with most things that have a random distribution, random really does mean random.

I have recently started working with my almost eight year old grandson to document the segments of his atDNA that match various ancestors using DNA Painter. This grandson has taken a deep dive into art. His Christmas wish list this year included only two words, “ART SUPPLIES.” Jonny Perl’s new award winning software, DNA Painter, is very graphically oriented and I was hoping it would capture the interest of this grandson. The first time we sat down to add segment matches to his skeleton genome, he asked me how long this was going to take. I told him it was going to take the rest of his life. I thought that might put him off; but the next time he came over for a visit he wanted to work on it some more.

We recently discovered a matching segment that stretched the limits of what we expected from atDNA. My grandson matched 3 women in the same area of chromosome 12. 
The Chromosome Browser tool at Family Finder (FTDNA) showed the shared segments.

Further investigation revealed that the three were related. The woman represented by the green segment above (31.24 cM) was Simon's 3rd cousin -- 4 times removed. Her common ancestors with Simon were a couple born before the Revolution in Pennsylvania: John Hoar (1766-1840) and Sarah Pearson (1766-1830). These were Simon's 6th great-grandparents (7 generations back).

The woman whose match with Simon was represented by the blue segment above (30.74 cM) was Simon's 4th cousin -- 3 times removed and the daughter of the previous match.

The the third woman was the granddaughter of of the first woman and daughter of the second. Her relationship to Simon was as a 5th cousin -- 2 times removed. The atDNA she shares with Simon overlaps what he shared with her mother and grandmother. However, she did not inherit the entire segment intact from her mother. Instead she received two segments of 9 cM and 12.11 cM with a significant gap between them.

One of Simon's two brothers also inherited the same pattern of atDNA matches with these three women. The other did not. 

Added support to the conclusion that my grandson's matches with these three distant cousins are the ones that contributed the segments of atDNA shown above can be found in my own results. I am two generations closer to them than are my grandsons. John and Hannah Hoar are my 4th great-grandparents. This puts us a little closer to the range within which we might expect to find legitimate atDNA matches. The three women are on paper related to me as: 3rd cousin -- twice removed; 4th cousin -- once removed; and 5th cousin.
Maybe random inheritance really does mean RANDOM.

Saturday, March 10, 2018

Spit or Swab?

Most of us who have done DNA testing have anecdotal impressions about the success of "spit tests" and "swab tests" for collecting DNA samples. Some of us may still have skepticism about whether a little saliva can provide accurate scientific results. On this later question, I was reassured shortly after we moved to Nashville in 2012. In late 2009 my wife and I had been beta testers for 23andMe when the company was expanding from health related testing to ancestry testing. As a result we both had pre-FDA intervention reports on multiple potential health conditions and drug interactions.

Although I wanted to believe the results, I was born in Missouri -- the Show Me state. Therefore, I had a bit of residual skepticism. Shortly after we arrived in Nashville, we enrolled in Vanderbilt University Medical Center's PREDICT program which aimed at matching drug reaction information with patients' electronic medical records. For this program blood was drawn in a clinical setting and was processed in the Medical Center's labs. On a half dozen comparable tests, both my wife and I got results and interpretations from Vanderbilt that validated those we have previously received based on 23andMe's spit tests. My wife was flagged for statins and I was identified as a faster than average metabolizer of certain blood thinners by both our spit tests and our blood tests. Saliva DNA tests seemed to work just fine.  

However, the question of whether spit tests or swab tests were more likely to get usable results in the lab still remained. My wife sometimes says that her family has a "no spit" gene. It took her three tries to produce a usable sample for Ancestry. It took her sister two tries at Ancestry. Their brother was never successful in producing a readable sample for 23andMe. After two tries the company refunded his money. 

I just retested a grandson a spit test for 23andMe and that result is still pending. The grandson is not biologically related to my wife's family. 

All four of the above family members have passed swab tests on the first try with MyHeritage or FTDNA. Most of you know that samples sent to these two companies are processed through the same lab in Houston.

The Poll:

How unusual is my wife's family? Maybe I should rephrase that. How unusual is their DNA testing success? To cast a wider net to collect some data I posted a poll this week on the "Genetic Genealogy Tips and Techniques" Facebook page which claims more than 36,000 members. For a variety of reasons this turned out to be a "quick and dirty" data collection survey. I was not clever enough to bend Facebook's poll instrument to allow responders to easily enter multiple results when multiple family members had been tested. All the data is self reported from customers. I tried to enter data customers provided in comments. My quick and unscientific poll ended up with 1.333 usable testing experiences.


While testing companies will claim a higher success rate than is shown in my results, I would welcome their data to prove it. Intuitively, these data seem to reflect what many of us experience. This is not intended to be the definitive final word on this question. What do you think?

I'd love to have more data. 


Saturday, February 17, 2018

Inheriting atDNA from 3rd Great-grandparents

Recently I have transferred to or tested about three dozen extended family members at MyHeritage. The recent upgrading of the tools by MyHeritage has moved the company's DNA services into the 21st century. If you haven't taken a look in the last month, you owe it to yourself to do so.

About a week ago I discovered a match from Germany for the maternal grandmother of my three Dowell grandsons. 

Those of you who are perceptive genetic genealogists will recognize that this amount of shared atDNA is well within the bullseye of what 2nd cousins would be expected to share. It also could be on the fringe of what could be expected if the two were one generation removed from each other within their families.

Particularly since my in law had been born in Germany, this appeared to be a match well worth pursuing. My interest was intensified when I discovered that "Weirauch" was one of the family surnames listed by the match.

Looking farther down the match list, I found my daughter-in-law:
She matched her mother as a daughter and shared a little less than half the atDNA her mother did. This would be about what we would expect because she was a generation farther removed from the matched individual.

Continuing down the match list I discovered my three Dowell grandsons. They were listed based on the amount of atDNA they shared with their maternal grandmother since it was her account I was using for this investigation. Those of you who read my blog posts a few months ago about how each of my grandsons inherited their atDNA from each of their four grandparents will not be surprised that MyHeritage reported their match with her ranged from almost 35% down to just over 23%. 

The boys are second cousins -- twice removed since the match is a second cousin of their grandmother. As such they would be expected to share about as much atDNA as third cousins and they do. However, I was surprised to find that the grandson who shared the most atDNA with his maternal grandmother, shared the least of the three with her second cousin. This is one more example to remind us of the random nature of atDNA inheritance. I guess I should learn not to assume predictability and just observe the data. 

Yes, this did turn out to be grandma's second cousin with whom communications had been lost when part of the family immigrated to America. A reunion is in the works that will include the grandparents, the parents and the grandsons during their spring school holiday in a few weeks. 

The source of the matching at DNA:

The connection of my grandsons with their newly discovered second cousin --twice removed is through a common descent from Max Weiranch (1878-1923) and Paulene Mittman (1878-1934) who were both born and died in Brieg, Schlesien. Max and Paulene were the boy's 3rd great-grandparents and between them they made a contribution that lives on in each of the boy's atDNA.


Each grandson inherited an identifiable and similar but different pattern of atDNA from this set of 3rd great-grandparents. 

Monday, November 13, 2017

FTDNA's Holiday Sale 2017

Some of you may have already noticed that the FTDNA Holiday Sale was launched yesterday afternoon. Below is the official company price list that was handed to attendees of the group project administrators conference immediately after the launch:

Those of you who have observed these sales for the last few years, have come to expect additional presents to appear on your FTDNA page each Monday during the sale which is expected to run through December.

When you click on the "Holiday Reward" icon, a discount code is revealed which is good through the following Sunday night Houston time. For example this week my coupon is good for an additional $20 off the sale price of a y67 marker test. If you manage multiple accounts, be sure to check each of them each week to maximize you chances to find the best discounts.

A secondary marketplace has already grown up to regift these "Reward" codes. If you received a y67 discount code as I did but instead need a mtDNA test, you can deposit your unneeded code(s) at locations like this site and "shop" for discounts on the tests you need. Check back often as the bigger discounts will be posted at any time during the week as more people log into their accounts for the first time that week or they decide they cannot use a particular test. There can be some strategy involved as you decide whether to take advantage of a small discount or wait a week or so as you hope to locate a larger discount.

Happy Holiday shopping to all of us as we cooperate to build our cousin matching databases to benefit us all!

Tuesday, November 7, 2017

With Great Haste We Make Slow Progress

FTDNA has been "evolving" our BIG Y results for a couple of months now. As a part of that process we were regressed back to the most recent ySNP for which we had tested positive separate from BIG Y. In my case that was back a little over four thousand years ago (R-DF13). 

This morning the evolution of my results has progressed to the point that my trail brings me down into the genealogical era again. It is good to be back. This process is not complete. The numbers in the right column will continue to increment as the results of others are "evolved" as well. It appears that about half of the results have now completed that process.  

My BIG Y Matching results are of November 7th
The three individuals with whom I am now showing matches on the bottom two steps share my surname and are also descendants through three different sons of my 6th great-grandfather who died in southern Maryland in 1733 -- clearly in the genealogical era. 

Another man who does not share my surname is expected to join the 3 matches on the second level when the processing of his results are upgraded in the near future. His family and mine were associated with each other in both Maryland and North Carolina. He was my earliest close STR match (an exact 12/12) when I first tested in 2004 and he is a 109/111 STR match today. I am eager for his results to be migrated so that I can further explore which of the three sons of my 6th great-grandfather his genome seems to be most closely associated with. Prior to Big Y testing, documents seemed to indicate that he was likely to be associated with the third son -- from whom I descend. In the first round of BIG Y testing he seemed genetically to be more similar with a descendant of the second son who's line never left Maryland. If that is the case, one of our biological paternal lines may have been rerouted around 1700 or before. I hope the new tools we are being given by FTDNA will help me sort this out.

I will be all ears and full of questions when I get to the 13th International Conference on Genetic Genealogy this weekend in Houston.

Friday, October 6, 2017

I Got It Wrong: A Retraction/Correction

Back on July 17th I published a blog with the heading How autosomal DNA is inherited: 3 siblings compared. At the time my son Jon was bothered by part of it related to the passing of DNA from great-grandparent to great-grandchild but I was too dense to comprehend his objection. Yesterday after more than six thousand seven hundred page views, Philip Gammon commented:

Hi, I'm surprised that no one has pointed out that calculation of the contribution from great-grandparents in the article is incorrect. The contribution of each pair of great-grandparents is not 25%, it is equal to the contribution the great-grandchild receives from the grandparent. This figure varies significantly as pointed out in the earlier paragraphs but this information is then ignored in the latter half of the article. 
This time I finally got the point. I wish to publically thank Philip for his initiative in bringing this error to my attention. I would like to think that many of the rest of my readers also noticed this incorrect conclusion on my part but were too kind to bring it to my attention. However, if we truly are going to consider ourselves to be citizen scientists, we must take on the responsibility offering constructive peer review of the work of our colleagues. That is how we all learn. What follows is a revision of that original post.

Inheritance of aDNA from grandparents:

If you know how much aDNA you inherited from a grandparent or great-grandparent, can you calculate how much you inherited from that person's spouse?

By now most of us know that each of us get half of our autosomal DNA from our mom and half from our dad. But how we inherit from earlier generations of our ancestors is less well understood. We are generally told after that first generation the inheritance pattern is random. However, we often see charts that show we should expect to inherit about 25% from each grandparent and 12.5% from each great-grandparent, etc. Are there any additional rules?

Below is a small case study that explores these issues:

Inheritance from maternal grandparents are shown in the left hemispheres above and paternal contributions are in the right hemispheres.

The chart above shows how much aDNA each of three brothers inherited from each of their grandparents. Only the middle one, Grandson 2, came close to the 25% average we might expect. However, note that each grandson inherited exactly 50% from his maternal grandparents and 50% from his paternal grandparents. However, the amount inherited from each individual within a set of grandparents varied considerably. The exact percentages can be seen in the table below.

As noted above Grandson 2 came the closest to the theoretical 25% inheritance rate. The aDNA inherited by Grandson 1 was skewed somewhat from that distribution. The practical implications for even this amount of variation can be important to your genealogical research. 

In this example the maternal grandfather is Ashkenazi -- a group that statistically has been over sampled in genetic genealogy databases. He had more than eleven thousand matches in FTDNA's Family Finder. The maternal grandmother came from an area in Eastern Europe very near the origin of her mate; but she was non-Ashkenazi. She had less than five hundred matches in Family Finder. The 4% difference in the amount of Ashkenazi DNA inherited resulted in Grandson 2 having more than five thousand matches while his full brother, Grandson 1, had about a thousand matches less. This also had a noticeable difference in their ethnicity predictions. 

When Grandson 3's Family Finder results are reported, it is expected that his matches and ethnicity predictions will vary ever further from those of his two brothers -- particularly Grandson 2. As we will see below, Grandson 3 inherited more aDNA from his great-grandfather -- the father of his maternal grandmother -- than the 15% he inherited from his Ashkenazi grandfather. This variation from the expected 25% from each grandparent could have been influenced by the preimplantation genetic screening process that selected a fertilized embryo that did not include an autosomal dominant gene that leads to a potentially fatal heart defect.  

All the results above are based on actual test results. However, if one of the grandparents had not been tested, we could have calculated their contribution. Even if two had not tested we could have calculated their contributions IF we had results from each of their spouses. You have probably already figured out that the contribution of the missing grandparent spouse would be 50% minus the contribution of their known spouse.

Inheritance of aDNA from great-grandparents: 

This kind of calculation becomes more relevant in the current case when I took a look at contributions from great-grandparents. We only have actual test results from one great-grandparent who was tested a decade ago about a year before he died in his mid 90s. So we can use his actual test results and also use them to calculate the aDNA contribution of his wife. By now you probably can guess that the hypothesized contribution of the non-tested great-grandmother will be constructed by subtracting his tested aDNA amount from the tested contribution of the relevant grandparent. The latter would equal the total contribution of each pair of biological great-grandparents.

For the oldest brother it turns out that the tested great-grandfather had contributed 12.4% of his autosomal DNA. This is very close to the theoretical 12.5%. In this case the grandmother had contributed about 28%. This left 15.6% for the great-grandmother to have contributed.

Great-Grandson 1

aDNA from great-grandparents

Grandson 1
Grandson 2
Grandson 3
Tested Great-Grandfather






Calculated Great-Grandmother



All other Great-Grandparents




In all cases the great-grandsons received more aDNA from the great-grandmother than they did from the great-grandfather. The tested great-grandfather had passed down 10.3% of the aDNA of the second brother and 16.6% of the aDNA of the third brother. In fact the 16.6% of his overall aDNA that the third brother received through his maternal grandmother and mother was more total aDNA than this brother had inherited from his paternal grandfather (15%, see above). This result was surprising but perhaps not unusual. We are preconditioned to expect that we received about one half the amount of aDNA from each ancestor in each receding ancestral generation. In this case that expectation was confounded because of the large amount of maternally inherited aDNA that the mother of the brothers had passed down to her third son. Although the mother had inherited half of her own aDNA from each of her parents, what she passed down to the third son had disproportionately over-represented what she had inherited from her mother by a ratio of more than two to one -- 35% to 15%.

The second son inherited less of the calculated contribution from his great-grandmother than either of his brothers in part because he inherited less of his grandmother's aDNA. He inherited 13.7% versus their 15.6% and 18.4%.

Great-Grandson 2

The third son inherited the most aDNA from the tested great-grandfather and did so by a considerable ratio. Although his 16.6% inheritance does not seem like a big difference from the 12.4% of one brother and the 10.3% of the other, it is about 35% more than one and 63% more than the other. In terms of inherited ethnicity and traits, these differences could matter. 

Great-Grandson 3

The Takeaways:
1. We inherit 50% of our aDNA from each parent; 50% from each set of grandparents; then what we inherit significantly different amounts from each set of great-grandparents, etc.
2. We often inherit significantly different amounts of aDNA from each member of a set of ancestors.
3. Even full siblings often inherit significantly different amounts of aDNA from each of their grandparents and great-grandparents.
4. These differences can significantly affect the numbers of autosomal matches reported for each sibling.
5. These differences can significantly affect ethnicity estimates.
6. These differences can significantly affect health and other heritable characteristics.
7. The contributions of some ancestors can begin to fade significantly within two or three generations while those of others can remain robust much longer.
8. If you have test results for at least one grandparent or great-grandparent, you can calculate the aDNA contribution of their partners.