Moshe-Mordechai van Zuiden
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Use and abuse of DNA to find (Jewish) ancestry

Illustrative. Jewish boys and men in the synagogue on Yom Kippur, by Maurycy Gottlieb, 1878. (Wikipedia)
Illustrative. Jewish boys and men in the synagogue on Yom Kippur, by Maurycy Gottlieb, 1878. (Wikipedia)

Fear of and abuse of DNA tests can be fought with information.

Most DNA is identical between all human beings. That’s how “the human genome” could be determined. Half of all our regular DNA we get from half of the DNA of one biological parent and the other half from half of the DNA of the other parent.

Yet, there are many tiny variations in the giant DNA molecules. DNA tests try to find these variations. Normally, almost half of them are passed on from father-to-child and almost half from mother-to-child.

There are several distinct categories of use of DNA in medical, legal or other cases. Let’s study them one by one. There are three distinct groups of DNA tests: individual, statistical general and statistical specific.



DNA is so individual that no two people have identical DNA. If a DNA sample matches another one 98%, you can safely assume the two samples are from the same person. If they differ 50% they are closely related (parent/child or two people who share grandparents).

It is very important, though, that cells from an investigator don’t contaminate the sample. Without clean work, this is worthless.

Recently, they found in the Netherlands a murderer of a decades-old cold case by collecting DNA samples of a whole population. The murderer had not supplied a sample but a close relative had.


Sibs get each about 50% of the DNA of each biological parent. However, each parent has 50% of each of their parents. The half that gets passed on is not the DNA from one grandparent. We each get a unique 50% of the mix our parents made of their parents two halves. Gen variations that sit in close proximity on a DNA strand, typically, will be inherited together. But in principle, great variations and surprises between sibs from the same biological parents are possible. Still, medical science will have no trouble pointing out consanguinity between DNA samples.


Spontaneous mutations may give rise to DNA variations that are not found in either biological parent. Don’t accuse parents of unfaithfulness for finding a strange DNA variation (like an unexpected blood type). Normally, a foreign gen will betray unfaithfulness (and then there will be many genes foreign to either parent) but sometimes it doesn’t

Most DNA changes don’t express themselves to the naked eye. They only show in a microscopic DNA analysis.

Most genes one inherits double, one from each parent. Some faulty genes only come out when both parents pass on a dysfunctional one. One healthy one in a duo from either parent may prevent many genetic illnesses. Therefore, it’s risky business to have children with close relatives, especially, the closer they are and if it’s done generation after generation. My excuses to the racial supremacists who want “pure breeds”: the more genetic unfamiliarity between the parents, the healthier and stronger the offspring. Inbreeding is very problematic.


Fathers who want to prove that they are not the biological parent often are motivated by a desire to dug child support. But the Israeli High Court has been very clear. If you were the social parent, you’re going to pay. This, because kids may suffer much more from a genetic test outcome than the alleged father and their interest takes priority. You lived with her, you pay. Such paternity tests are forbidden to be done in Israel!



In the past, most people had children with locals only. Over centuries, DNA variations became typical of certain locations. This also works for populations that did migrate a lot but didn’t intermarry (Jews). This should not be confused with certain groups looking the same.

On a smaller scale, these apparent similarities of groups are mostly caused emotionally, by customs, habits, attitudes, and circumstances — not genetically. The Dutch look so seriously because of the bad weather and Calvinism, not through DNA.

On a larger scale, apparent similarities are often genetic, like the shape of the head and eye, hair, and skin color, etc. However, such differences are often not one-on-one as they are caused by many genes (DNA locations). So can many children of two dark parents have many shades of skin color, up to pink. And four Caucasian grandparents may still have a dark-skinned grandchild, even with all the couples being faithful.

The DNA-variations arise rarely and randomly. Normally, they are not viable, but when they are, they are often passed on to the offspring. They seem to occur in more or less the same frequency. Specialists use that, to estimate how long ago people had a common ancestor.


These commercial DNA-tests to check out ancestry, make use of what we mentioned above, that in the past, most people traveled little (or didn’t marry out. They had children with “their own” and over centuries, certain DNA variations became typical of certain groups.

If one has many genes with variations that are typical of a certain population, probably one or more recent ancestors came from there. The lesser the number of variations typical of a certain group, the farther away we expect such ancestors to be. But, this is all statistics, not direct causation. Especially, when only a few similarities point to ancestors from place A, it can either mean a distant relative from A or be a pure coincidence, having some of these variations from some place B and some of the others from a place C, without any ancestor from A.

Also, not the whole DNA is compared intact. It’s first cut up by enzymes into small pieces. Then is cataloged what pieces there are. In other words, this method is very imprecise. Which shows when you’ve done it twice. Or when identical twins have it done. Or when you go to two different firms. The latter point especially, because the “results” much depend on the database that a company works with.

“You were found to have 3% Jewish and 1.4% Native American DNA” should be taken with a truckload of salt.


Multi-Generational Paternity

One day, one Cohen said to himself, isn’t it strange how different we Cohanim all look being from one Tribe. I wonder what our DNA says.

While people can become Jewish, being a Cohen, one can only inherit from one’s father. If only we could examine DNA that goes from father to son to grandson, etc.! Well, we can. That’s the Y-chromosome.

Biological women have two X-chromosomes (XX), the one from their father (XY) and one of the two from their mother (XX). They give either of them to each of their children (XX/XY). Biological men (XY) have one of the X-chromosomes from their biological mother (XX) and the Y-chromosome from their father (XY). Everyone has at least one X-chromosome (XX/XY) but only biological men have a Y-chromosome (XY). (For simplicity, we omit from our story here the genetic Intersex, people with other sets of sex chromosomes: X0, XXY, XYY, XXYY.)

The Y-chromosome is the smallest one of all, having almost no genetic information that we know of. Yet, if it’s missing or accidentally gets doubled, pandemonium breaks loose (sex attributes, fertility). So, though the Y looks like a defective X-chromosome, let’s not squander it.

Priestly Tribe (Cohanim)

If all Cohanim come from Aharon the Priest, their Y-chromosome variations should be very similar.

They checked many Cohanim. They indeed found such similarities in a high percentage (85%?) of Cohanim. However, that doesn’t mean that we now have a test to determine who’s a Cohen. And these are the many reasons:
* The common ancestor who was found most probably wasn’t Aharon. It could be someone earlier or later in the family tree. Later means that there are Cohanim with other X-chromosome variations. Earlier means, there are non-Cohanim with the “Cohanim Y-chromosome.”
* Spontaneous mutations could have men unjustly seem part or not part of this group.
* The “Cohen Y-chromosome” is also found in Gentile men. There is no reason to assume that all these men stem from Cohanim who married out, Heaven forbid. In any case, Tribal-ship is inherited from the father but Jewish-ness through the mother (see below) and comes first. If someone is not a Jew, he may become a Jew but never a Cohen.
* Jewish Law says that whoever comes into a new community and says and maintains for a month that he’s a Cohen, he’s believed. (Although it’s a great honor to be from the Priestly Tribe, it gives so many extra obligations and expectations that no one is suspected of making this up.) We can’t throw out Jewish Law and replace it by a trick. Only the Messiah may pinpoint anew the Tribe each Jew actually belongs to. He may also point out Gentiles to be Jewish that the Rabbis could not grant.

Yet, I know a very pious Jew with ancestors from a Polish village who has the same family name as only Cohanim had in that village but who, thanks to the Holocaust, has no proof that his father’s father was a Cohen. If I were him (which I am not), I’d have my DNA checked. If it did not hold the known Y-chromosome variations, I would be still in limbo. But if it had the majority Cohen variations, I’d proclaim myself a Cohen. (His un-eagerness to check this out, confirms to me how reluctant even the most dedicated Jews are to take Priesthood upon themselves.)

Multi-Generational Maternity

As just mentioned, for Jewish Law, Jewish-ness is inherited through the mother. If only there was a genetic test to see who’s the mother of the mother of the mother … Well, there is.

Remember, of the X-chromosome that biological women have double (XX), one comes from their biological father (XY) who got this from his biological mother (XX), while the other comes from their biological mother (XX) who got this one from either her biological father (XY) or her biological mother (XX). So, X-chromosomes travel between the biological sexes. But — surprise, surprise — there is genetic material that stays almost only with the mother!

A major difference between a sperm cell and an egg cell is that the former is mostly DNA and a tail while the latter has the same amount of human DNA plus cell fluid with microscopic inclusions. One of those happy inclusions is the mitochondrion. This functions in animals a bit as the chloroplast in the green plant cell. It takes care of the energy supply to the cell. These mitochondria are creatures in their own account and they have genetic material of their own onboard. With variations!

So, if we check out generic variations to our mitochondrial DNA, we can trace back each, our mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s mother’s (etc.) origin.


This is exciting but not a watertight proof for Jewish ancestry:
* Sometimes, a mitochondrion takes a hike within a sperm cell, upsetting the whole nice test we had thought out.
* Many have become Jewish with no Jewish ancestry at all. They are perfectly Jewish and for Jewish Law, there is no difference between Jews whose ancestors became Jewish and whose were Jewish from birth. It is wrong to make such distinctions. Judaism lends no hand to racism.

It was found that many Jews have a common ancestor but it’s too loose to call her the Matriarch Sarah. And many humans have a common African Ancestor but it’s too slipshod to call her Eve.

So, the proper use of genetics to check someone’s Jewish ancestry is:
* If there is much DNA variation that we see among Jews, this may support the idea that someone is Jewish. But, he could have had three Jewish grandparents while his mother’s mother was a Gentile. So, such signs are more conclusive if we also have proof that the father had no Jewish parent and the mother’s father was not Jewish either.
* If there is little DNA variation that we see among Jews, this may never be taken as proof that someone is not Jewish.

So, a positive outcome may encourage someone to work toward conversion, further support a giur legumra (conversion to be certain) or promote making more effort to try and find real proof.

But, a negative outcome of such a test can never rule out if someone is a Jew. Not even make it less likely! It is very important that rabbis who’d want to work with this, understand this last point. Especially, when we consider what we saw above, that these tests are merely statistical and only very rough. They’re not as conclusive as individual DNA tests can be. A genetic profile is as inconclusive as someone’s face or bodily profile. There are many Jews who look a certain way — and many who don’t.

A few clear examples of how inconclusive these DNA tests are:
* A grandmother properly became Jewish and had no Jewish ancestry and had children with a Gentile. Their daughter married a Gentile. Her children have no “Jewish DNA” but are fully Jewish under Jewish Law.
* A woman had 3 children. She then became Jewish and had 3 more kids. Genetically, the 6 siblings are similar, but 3 are Jewish and 3 not.

NB: Even in a Jew, these variations found in many Jews do not make someone Jewish. Jewish-ness is not encrypted in the DNA. What is called “Jewish” is often immigrants looking differently from autochthon Gentile communities or special attitudes. Jewish character traits are surely inherited, especially through the mother (from nine months “lying under a Jewish heart”), but not via DNA. Kids learn them through “osmosis.”


As most inventions, DNA tests may be used for the good and abused. Armed with knowledge of the above, we can spot and protest abuse.

About the Author
MM is a prolific and creative writer and thinker, previously a daily blog contributor to the TOI. He often makes his readers laugh, mad, or assume he's nuts—close to perfect blogging. He's proud that his analytical short comments are removed both from left-wing and right-wing news sites. None of his content is generated by the new bore on the block, AI. * As a frontier thinker, he sees things many don't yet. He's half a prophet. Half. Let's not exaggerate. Or not at all because he doesn't claim G^d talks to him. He gives him good ideas—that's all. MM doesn't believe that people observe and think in a vacuum. He, therefore, wanted a broad bio that readers interested can track a bit what (lack of) backgrounds, experiences, and educations contribute to his visions. * This year, he will prioritize getting his unpublished books published rather than just blog posts. Next year, he hopes to focus on activism against human extinction. To find less-recent posts on a subject XXX among his over 2000 archived ones, go to the right-top corner of a Times of Israel page, click on the search icon and search "zuiden, XXX". One can find a second, wilder blog, to which one may subscribe too, here: or by clicking on the globe icon next to his picture on top. * Like most of his readers, he believes in being friendly, respectful, and loyal. However, if you think those are his absolute top priorities, you might end up disappointed. His first loyalty is to the truth. He will try to stay within the limits of democratic and Jewish law, but he won't lie to support opinions or people when don't deserve that. (Yet, we all make honest mistakes, which is just fine and does not justify losing support.) He admits that he sometimes exaggerates to make a point, which could have him come across as nasty, while in actuality, he's quite a lovely person to interact with. He holds - how Dutch - that a strong opinion doesn't imply intolerance of other views. * Sometimes he's misunderstood because his wide and diverse field of vision seldomly fits any specialist's box. But that's exactly what some love about him. He has written a lot about Psychology (including Sexuality and Abuse), Medicine (including physical immortality), Science (including basic statistics), Politics (Israel, the US, and the Netherlands, Activism - more than leftwing or rightwing, he hopes to highlight reality), Oppression and Liberation (intersectionally, for young people, the elderly, non-Whites, women, workers, Jews, LGBTQIA+, foreigners and anyone else who's dehumanized or exploited), Integrity, Philosophy, Jews (Judaism, Zionism, Holocaust and Jewish Liberation), the Climate Crisis, Ecology and Veganism, Affairs from the news, or the Torah Portion of the Week, or new insights that suddenly befell him. * Chronologically, his most influential teachers are his parents, Nico (natan) van Zuiden and Betty (beisye) Nieweg, Wim Kan, Mozart, Harvey Jackins, Marshal Rosenberg, Reb Shlomo Carlebach, and, lehavdil bein chayim lechayim, Rabbi Dr. Natan Lopes Cardozo, Rav Zev Leff, and Rav Meir Lubin. This short list doesn't mean to disrespect others who taught him a lot or a little. One of his rabbis calls him Mr. Innovation [Ish haChidushim]. Yet, his originalities seem to root deeply in traditional Judaism, though they may grow in unexpected directions. In fact, he claims he's modernizing nothing. Rather, mainly basing himself on the basic Hebrew Torah text, he tries to rediscover classical Jewish thought almost lost in thousands of years of stifling Gentile domination and Jewish assimilation. (He pleads for a close reading of the Torah instead of going by rough assumptions of what it would probably mean and before fleeing to Commentaries.) This, in all aspects of life, but prominently in the areas of Free Will, Activism, Homosexuality for men, and Redemption. * He hopes that his words will inspire and inform, and disturb the comfortable and comfort the disturbed. He aims to bring a fresh perspective rather than harp on the obvious and familiar. When he can, he loves to write encyclopedic overviews. He doesn't expect his readers to agree. Rather, original minds should be disputed. In short, his main political positions are among others: anti-Trumpism, for Zionism, Intersectionality, non-violence, anti those who abuse democratic liberties, anti the fake ME peace process, for original-Orthodoxy, pro-Science, pro-Free Will, anti-blaming-the-victim, and for down-to-earth, classical optimism, and happiness. Read his blog on how he attempts to bridge any tensions between those ideas or fields. * He is a fetal survivor of the pharmaceutical industry (, born in 1953 to his parents who were Dutch-Jewish Holocaust survivors who met in the largest concentration camp in the Netherlands, Westerbork. He grew up a humble listener. It took him decades to become a speaker too, and decades more to admit to being a genius. But his humility was his to keep. And so was his honesty. Bullies and con artists almost instantaneously envy and hate him. He hopes to bring new things and not just preach to the choir. * He holds a BA in medicine (University of Amsterdam) – is half a doctor. He practices Re-evaluation Co-counseling since 1977, is not an official teacher anymore, and became a friendly, powerful therapist. He became a social activist, became religious, made Aliyah, and raised three wonderful kids. Previously, for decades, he was known to the Jerusalem Post readers as a frequent letter writer. For a couple of years, he was active in hasbara to the Dutch-speaking public. He wrote an unpublished tome about Jewish Free Will. He's a strict vegan since 2008. He's an Orthodox Jew but not a rabbi. * His writing has been made possible by an allowance for second-generation Holocaust survivors from the Netherlands. It has been his dream since he was 38 to try to make a difference by teaching through writing. He had three times 9-out-of-10 for Dutch at his high school finals but is spending his days communicating in English and Hebrew - how ironic. G-d must have a fine sense of humor. In case you wonder - yes, he is a bit dyslectic. If you're a native English speaker and wonder why you should read from people whose English is only their second language, consider the advantage of having an original peek outside of your cultural bubble. * To send any personal reaction to him, scroll to the top of the blog post and click Contact Me. * His newest books you may find here:
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