Finding "cousins" through personal genomics

The odds of knowing your cousins: 23andme Part 1:

Bizarrely, Jonathan Zittrain turns out to be my cousin -- which is odd because I have known him for some time and he is also very active in the online civil rights world. How we came to learn this will be the first of my postings on the future of DNA sequencing and the company 23andMe.

Just read the whole thing. This is really a matter of the humanities, not science. Specifically, the almost mystical significance people seem to put into the finding that they share genetic ancestry with people, even people who they knew and were friendly with before they knew this datum.

Also, I think this sort of thing makes hang-wringing about the ethical conundrums that genetic counselors might have in regards to paternity issues which a wife might know of, but the husband might not, seem totally ridiculous. With the plethora of personal genomic data which will likely be part of everyone's information portfolio circa 2020 you'd have to be retarded, or very exceptional, not to notice a "extra-pair paternity event" within a family.*

H/T Dr. Daniel MacArthur.

* Exceptional as in the putative father is dead, and all his relatives are dead, or he has no relatives (e.g., only child whose parents were only children, etc.).

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Hmm, you take a rather odd spin about mystical importance from an article where I wrote: "Most people donât have much contact with 3rd cousins or care much to. Itâs not a very close relationship."

That most people, perhaps I should have said more strongly, includes me. I was once approached by a 3rd cousin who lived in my town who told me we were 3rd cousins. My reaction was, "so?"

The cousins identified via DNA are interesting to me because they are friends with common interests. Jonathan has more in common with me than most closer family.

I will be writing in part 2 about the exposure of family secrets, but I don't agree that the concern about it is ridiculous. In many cases people took actions only after promises of protected anonymity -- contractually and often statutorily when it comes to sperm donations and adoptions, and personally when it comes to infidelities. People will not be breaking their word, but technology will unmask, and some families and relationships will suffer serious damage. Hand-wringing over that is not so ridiculous.

And I say that even though the 3 reunions with genetic parents in my own extended family were quite positive.

Perhaps what you label a mystical significance is simply the interest in nature/nurture questions, and whether unknown family became friends (or entered common social circles) at an atypical rate for some reason relating to shared genes. I think that's interesting.

And mostly I think it's interesting to examine the odds of events which seem intuitively unlikely, and figure out if they are, or what the reason for them is.

Part 2 will be posted early next week.

brad, i wasn't talking about you specifically re: mysticism. and the fact that people know that they share a region of the genome identical by descent does has a weird power over people. perhaps it will fade over time, but the popularity of genetic genealogy shows that there's something there beyond science.

as for whether hand-wringing is ridiculous, it is ridiculous because many people presume that there is some way to forestall this by fiat or ethical guideline. the fact that anonymous sperm donors have already been tracked down via inferences from genetic technology in our primitive state attest to this (e.g., kids finding each other through these databases, and triangulating to who the donor might be through fragments of different data they have).

I think that Brad's finding cousins might be an ethnic function (or family function) of likeliness to be tested. I know all of my first cousins and their kids, and many of my other second cousins, and I know where most of the 3rd and 4th cousins would be, and very few of them are at all likely to be tested based on what I know about them. (I.e., most live in rural Iowa, Missouri, and Arkansas and are conservative Christians.) Out of the 30 or 40 closest relatives, I can think of 2 who might conceivably have wanted to be tested, but one of them died several years ago. It's really a rather elite form of entertainment.

By John Emerson (not verified) on 07 Mar 2010 #permalink

Annoyingly barely related or hugely related but on blog topic. Is there any papers on this news? Sounds like serious wanderings leading to really isolated lingering culture. Continued travelers along the coasts of Africa south from Ethiopian Jewish settlers?

Lost Jewish tribe 'found in Zimbabwe'

How you cherish cousins may depend on how many you have. My mother had 29 first cousins and probably didn't even know them all, yet alone her second cousins. I had zero first cousins.

My mother was a witness for the bride in a wedding in which the groom was her second cousin. Circumstances indicate that she didn't know he was a cousin. The bride, who lived next door to my mother, was the sister of a woman that was married to my mother's eldest maternal uncle. The youngest son of this marriage became a friend of mine about 25 years ago, in large part because we had an aunt in common and were, in essence, cousins-in-law.

In retirement, I worked on the genealogy of my family and discovered that one of my great grandmothers was the sister of one of my friend's great grandfathers, making us third cousins. Being that all Homo sapiens are related, there is nothing mystical about it, but it was interesting, nevertheless, to learn that a cousin-in-law was also a third cousin. So if you have no first cousins and your second cousins are all folks you've never met, some of your third cousins can be special.

By Bob Carlson (not verified) on 07 Mar 2010 #permalink

It seems odd to me that people are supposed to be third cousins but can't find the actual family link. I could certainly figure out if someone was descended from a grandfather's cousin by talking with them and comparing notes.

My father went through this from the genealogy end and what I concluded from his experience is that blood relationship isn't such a big deal. There are really only one or two of my first cousins I ever could have been close friends with, at most. And a cousin I know in Iowa lives a mile down the road from a cousin I don't know, and the two of them never speak if they can help it.

By John Emerson (not verified) on 07 Mar 2010 #permalink

I have become interested in genealogy in the last few years, and find it to be quite a fascinating pastime. I haven't come across any distant cousins yet, since the vital statistics and census data are usually not made public until the people they describe are dead. I haven't tried the personal DNA thing yet. I already know who my great grandparents were and where they were born, so I don't see that the DNA thing would give me much information. Besides I'm female, and have no brothers and don't know any surviving male relatives (other than my sons) As I understand it the test is most useful for males to trace their paternal line, and if are a female with no male relatives it won't tell you much. Is that correct?

"It seems odd to me that people are supposed to be third cousins but can't find the actual family link."

Could historically extensive inbreeding among Ashkenazi Jews have created a situation where people who are not genealogically third cousins are approximately as genetically similar as third cousins?


That was true for old-school genealogy/ancestry tests based on the Y chromosome and mitochondrial DNA (inherited solely along the paternal and maternal lines, respectively). 23andMe's test is far more useful: it's based on over half a million markers selected from throughout your DNA, so it's able to pick up a much larger variety of relationships, and with far better accuracy than older tests.

for the mysticism part, see this:

jump to the end. henry louis gates and his had both have their full genomes sequenced. then, they infer the genome (or at least half it) of gates' dead mother by yanking out the section which is disjoint from his father's genome. gates is freaking out and getting all emotional, as he's "seeing his mother" again.

and people accuse me of being a genetic determinist???

i assume a lot of this will abate as genomics becomes more ubiquitous day to day, like in vitro fertilization (who says "test tube babies" anymore???). but there's a bigger picture of the impending operational lack of privacy and the transparent society. though residents of britain, such as dr. macarthur, are already a bit further on when it comes to being recorded in public places.

Megan, The Ethiopian Jews don't appear to actually descend from Jews. at least not from the same Jews that most other Jews descend from (iow, if they ever purposely meant to practice "Judaism" at all, they descend from converts). As for the Lemba, news on them has been around for a while. I'm tempted to dismiss the cohen gene bit among them but I don't see anyone else doing it, so it seems most likely that many of them do in fact have it. This doesn't mean of course that they descend from some "group" of Jews (as obviously they don't) only that their paterfamilias going all the way back was likely Jewish. There were many Jewish traders over the millennia (some researches would claim that Great Zimbabwe wasn't entirely the product of the locals) and it isn't hard to imagine that many traders - Jewish and otherwise - "knew" some of the locals in a Biblical sense and sired seed who were regarded as, and actually were, smarter than the locals and thus had greater opportunities to procreate and spread their gene to the next generation.

the Y lineages are obvious west eurasian, and i believe cohen modal. but there's debate about how jewish cohen modal is, so there's a non-trivial probability that they're descended from other middle easterners, probably from yemen or oman.

Razib, do you know what percentage of people have been decieved as to who their real father is in the United States. Even if it is as low as a percent or two I'd think it would be a legal cloud hanging over the genomics business. Also when they make a misdiagnosis like they probably did with Larry David when he was told he is 3/8ths american indian it stongly implies his jewish father isn't his father. It is a touchy subject, anybody have thoughts on this.

By dave chamberlin (not verified) on 08 Mar 2010 #permalink

It's sort of fun tracing traits within the immediate family though. Several members of the family have a lop ear (curled over on the top) and that showed up on a grandnephew. My sister and eye have several of our father's minor medical conditions.

My brother has two genetic condition, one leading to glaucoma and a very rare one making his fingers hard to straighten past a certain age. Both treatable.

By John Emerson (not verified) on 08 Mar 2010 #permalink

The percentage may be quite high. Jared Diamond reports, around page 86 in "The Third Chimpanzee" of a repressed study done in the 40s on blood groups. The researcher found 10% of chidren born in various hospitals had a blood group matching neither father nor mother! As you can't tell anything when the group matches the mother, it suggested a productive infidelity rate of perhaps 14%, which was so politically incorrect the study was not released, or so he says.

(I will presume he knew that As and Bs can be AO and BO, allowing O to come from any combination of A, B and O, but two Os can have nothing but O, and ABs can't have O.)

While I would bet the number has gone down in the world of modern birth control, it's a big number.

Also, 2.5% of children are adopted. I don't know if there are stats on how many of them know this and how many don't, and when they learn.

Thank you for your answer. I just hope the personal genomics business isn't seriously hampered by frivilous lawsuits in the future. I've heard that ladder manufactorers have fiscal years where they spend more on defending themselves in lawsuits than the actual costs of manufactoring ladders.

By Dave Chamberlin (not verified) on 09 Mar 2010 #permalink

Well I've nothing but good things to say about 23AndMe, and continue to be very satisfied with the service they offer.

23AndMe's Relative Finder is now my #1 destination every day, to see who has shown up as a relative, and compare notes with relatives.

I am Irish born and raised with all my ancestors being in Ireland for the last 350 years at least, with little or no emigration in the family. I knew of one relative in New York, a second cousin who grew up outside London, and accidentally met a fourth cousin in Brooklyn, who lives near me. I also knew that my Dad had a grand-uncle who was one of the first settlers in Iowa.

However Relative Finder has found 200 relatives to date, of which 195 are from the US, 3 UK, 1 Ireland, 1 NZ, 1 Aus. What's fascinating is that most of my relatives are not in the major Irish urban areas of the US, but instead in the US South, particularly the Carolinas, and generally in the South and New Orleans. I also have a at least 3 African-American, and 5 Jewish and 1 Muslim relative - though it seems that the majority of my relatives would identify as Anglo-Saxon Protestants . I also have about 20 relatives who identify as German American, all in the Southern US, and am trying to determine whether they have some "Palatine German" Irish ancestry - as I grew up 12 miles from what once was a major Palatine settlement in Ireland.

Additionally, of the 35 relatives I am sharing with, about 10 are college professors and many are fellow techies, and one the former CTO of a major social networking company - I'm guessing that selection bias plays into this, but it's still fascinating that so many are involved in the very areas I'm interested in, and I'd have to attribute some to shared genetic inheritance.

On a more mundane level, 23AndMe indicates I have a 300% elevated chance of developing Prostate Cancer. My Dad is receiving treatment for Prostate Cancer right now, and his uncle died of this. While a predicated 4th cousin relative on my Dad's side, whom I was in contact with a few days ago, says that her father was treated for this, and her grandfather died of it.

I've just had my daughter tested, and it's so interesting to actually "see" what she has inherited from me and what she hasn't. My daughter's Mom is of French/Italian - actually Northern Italian, Corsican, Breton and French descent by her 4 grandparents - and I'm largely Irish, with some Anglo-Irish, Viking and Norman. While my daughter is predicted to be German/French, based on her Ancestry Informative Markers (AIM's), fascinating.

Now I'm really tempted by 23AndMe.

I am the opposite to pcontroy. I absolutely consider 23andMe a flim flam company. I went to 23andMe to find out my ancestry. Not who were my parents, grandparents, great grandparents and so on. I know that. I wanted to know the parts of west Eurasia I come from going back to 10,000 years. I know my ethnic group, nationality, pedigree, haplogroups and other genetic details. What did 23andMe give me? Basically just my raw SNP results, a few prognostications on my health risk status and RF cousin feature. I did not want the health risk assessment which I consider useless, and as far as cousins are concerned, I don't even think of my mother's or father's sibling's children as my cousins. I don't have a family gene. All that interests me are my children, my parents and my siblings. Anyone else can go jump off the Empire State Building. No mysticism there. The Community board at 23andMe is full of hypochondriacs, and various ethnic Princesses with a supposed origin east of Greece in Europe. 23andMe's customer base is very limited, not just in intelligence or mental maturity but in its ethnic spread. The biggest groups are the mixed Central and Northern European Americans, and Ashkenazim Jews. I belong to neither, and comparing myself with them is about as useless as comparing myself with Andaman Islanders. I could go on but I will stop.

I recommend you choose another company, deCODEme comes to mind, but there are others.


In terms of Relative Finder, being Irish, British or German will yield about 100-200 relatives. Being Finnish will yield about 500, but being Ashkenazi will yield 800-1,000 - and I know of one AJ guy with over 2,000 relatives.

Since I know you belong to a population with is almost a genetic isolate, the chances of finding relatives would be rare - is that what you're complaining about? Or is it that the relatives found were not what you thought they would be?

If I take you at your word that you are not interested in the health aspects or relatives, then this service almost certainly wouldn't match your requirements.

I have also uploaded my data for free to deCODEme, and their site is in great need of an information architect, as the layout and navigation are poor, and overall the site is not user friendly, and has almost no discussion. Having said that, what the do offer - that 23AndMe doesn't - is a wide array of sample populations worldwide to compare oneself against, and yes this is a very interesting feature.

For some reason though for Europe, they leave out the Irish, British and Germans - which is a bizarre oversight if you are hoping to market to the US population??!!

Of the 9 populations listed in Europe, I match as follows:
1. French
2. Icelandic
3. Orcadian
4. Italian
5. Russian
6. Basque
7. Tuscan
8. Sardinian
9. Adygei

Which was a surprise to me, as usually Orcadians are used as a proxy for British in many studies?! So I guess I have more Norman/French ancestry than I expected.

It's also interesting to see that among East Asians, my top 3 matches are:
1. Yakut
2. Tu
3. Mongolian

Most interesting is South West Asia - which is the homeland of the first agriculturalist in Europe and probably where West European R1b derived from, my top 5 matches there are:
1. Druze
2. Pathans
3. Palestinians
4. Brahui
5. Sindhi

So a Levant connection, followed by Pakistan...