Comment by danans | Hacker News Reader

Comment by danans | Hacker News Reader

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> And you can be certainly be Jewish without having Jewish DNA, but there’s some controversy as to whether the reverse is true.

What's the controversy? Biologically there's no such thing as "Jewish DNA". It's just a shorthand for "Human DNA haplotypes (AKA markers) that occur at significant frequencies among populations that identify today as Jewish".

For example, the YDNA haplotype J1, while it occurs at high frequency among Jewish populations, occurs at even higher frequencies among many non-Jewish groups in the Middle East and surrounding areas[1]. It's only somewhat distinctively "Jewish" in areas where Jewish people are a minority like Europe.

Furthermore, the emergence date of this haplotype 17-24k years ago predates the existence of the ethno/religious/cultural identity known as "Jewish" by almost 20,000 years.

Therefore the reverse/opposite of the statement, something like "you can have Jewish DNA and not be Jewish" is either trivially true or nonsensical.

1. https://en.wikipedia.org/wiki/Haplogroup_J-M267

Scientists have no right to declare what does and does not exist based on what their machines are able to detect. Did gravity not exist before the LHC was constructed and the Higgs data analyzed?

Jewish DNA is that which has descended from Abraham, through Isaac, to Jacob and the Jewish nation. Gravity is an attraction between masses. These things exist – regardless of your machines’ proclivities.

> Jewish DNA is that which has descended from Abraham, through Isaac, to Jacob and the Jewish nation. Gravity is an attraction between masses. These things exist – regardless of your machines’ proclivities.

Including the term "DNA" in that statement is an anachronism.

Cultural identification isn't a physical law like gravity, regardless of how aggressively or emphatically that may be stated. That doesn't make it unimportant or irrelevant, but it is not a biological fact, but instead a social fact.

Are you specifically claiming that a common ancestor does not exist, or that genetic information does not spread to offspring?

> Are you specifically claiming that a common ancestor does not exist, or that genetic information does not spread to offspring?

I'm not making either of those claims. The first is an article of faith, and the second is trivially true.

I'm stating that one can't claim a particular set of DNA patterns makes someone "Jewish", because DNA is a biological phenomenon, and ethnicity/culture/religion are cultural phenomena.

You seem very unaware of how the Jewish tribe works. Genetics and family line tracing are very much a core concept.

I'm aware of family line tracing for establishing tribal identity. It's not something unique to Judaism.

DNA patterns often reflect the history of rigid social organization patterns like tribes (and indeed are essential for genetic risk management provided by organizations like Dor Yeshorim).

But nobody was tracing ancestry using DNA until the latter half of the 20th century, so claiming DNA as a basis of tribal identity seems quite anachronistic.

What is your claim exactly? It seems as if you think somehow DNA didn’t exist as a means of transferring genetic information to offspring prior to it being discovered. I can’t imagine you actually think that, so I’m at a loss for what your point might be.

> It seems as if you think somehow DNA didn’t exist as a means of transferring genetic information to offspring prior to it being discovered.

No that's not what I said. I said that DNA, though inherited, is irrelevant for determining cultural identity.

If I discover tomorrow that I carry YDNA haplotype J1, that doesn't make me Jewish, either culturally or ancestrally. Nobody could claim me as ancestrally Jewish based on that either.

Having a documented lineage stretching back many generations, however, would possibly do both, should I choose to embrace it.

You’re the only one here fascinated with this haplotype. Which is odd, considering you yourself call it inconsequential. Nobody but you has equated it with anything, and you have specifically said it does not equate to anything. So all in all this is just a textbook strawman, which I have no interest in further considering.

> You’re the only one here fascinated with this haplotype. Which is odd, considering you yourself call it inconsequential.

Then substitute it with haplotype G or E1b, or include all of them. Or swap out both the haplotype and the cultural group for different ones, i.e Y Haplogroup R1b among people from Iceland.

The particular haplotype is irrelevant to the argument, which is that genes don't define cultural identity, and at best are trailing and largely low resolution indicators of historical social patterns.

Again, you’re letting your machines decide what information exists, rather than accepting they might not have the capability of deciphering all that is out there.

Even if Abraham _did_ exist, at this point in time it's like trying to distinguish a drop of water from the ocean it's now living in. That's how little would have remained of Abraham's DNA so much later.

If this were true, genetic testing wouldn’t be able to identify folks as Ashkanazi Jewish, for instance. But it can. And many phenotypes do the same.

I was replying to the claim that Abraham's DNA (if he existed) could be traced in today's Jewish population. And that _is_ impossible. In any case, it's not like you identify Ashkanazi Jews from DNA, instead it's that when DNA-checking people who self-identify as Ashkanazi then you find Middle Eastern ancestry. To recite Wikipedia's citation: '.. while certain detectable Middle Eastern genetic components exist in numerous Jewish communities, there is no evidence for a single Jewish prototype, and that "any general biological definition of Jews is meaningless"'

There is no common ancestor. Abraham is a mythological character.

If you personally are a direct descendant of Abraham, or any other specific individual who lived approximately 3000 years ago, statistically you do not carry any DNA from that ancestor. While there are some nuances relating to differences in how the different sexes pass on their genes, as a rough approximation you carry half the base pairs of each of your parents, who each carry roughly half from their parents, and so on. So you carry 1/2^n base pairs from an individual n generations before you. The human genome is 3 billion base pairs, meaning in 31 generations the odds of having a single base pair from a specific ancestor is about 50%. 3000 years is about 120 generations, so your odds of having a basepair from a specific ancestor that far back are about 1 in 1,000,000,000,000,000,000,000,000,000. The only exceptions that matter on that timescale are the y-chromosome along the male-only line descent and the mitochondrial DNA along the female-only line of descent.

So by that logic nobody has any DNA in common with neanderthals, right? Try again. You’re missing a big, big, gotcha.

No one has any DNA that can be traced to a specific Neanderthal, no.

Of course people have DNA in common with their ancestors as a group, hell we share a lot in common with fish. But it's because these genes are common that they enter and re-enter your family tree at multiple points.

And your mitochondrial DNA definitely doesn't descend from Abraham, a male incapable of passing on mitochondrial DNA, so there's a reason I gloss over female line descent.

Your pseudoscience above would make it seem nobody has any DNA from any ancestors at all, as there were not your 10^Whatever creatures ever in existence. Once you figure out the bug in your logic there, you will perhaps see the failure of the rest of your argument. Hint: inbreeding.

It's actually called pedigree collapse, but it doesn't really change anything - the fact that the same ancestor may appear in multiple places in your family tree makes it harder to trace a gene back along any given line, not easier. You undoubtedly share an enormous amount of genetic similarity with Abraham, it's how you got it that is forever scrambled.

It nullifies your entire diatribe and all of its bogus numerics, but O.K.

Good sign of someone arguing dishonestly is that when you call out their lies, they tell you that the truth doesn’t matter.

Aside, Jewish line is determined by matrilineal descent. By your own logic the mitochondrial DNA is shared, which is a rather significant aspect to simply gloss over.

Are you literally saying they all share a single ancestor? Because that is unlikely to be true

Is it? I'd imagine they all share many common ancestors, but that those common ancestors are probably shared by many others as well so it's not very unique.

30 generations back (a thousand years?) you have over a billion ancestors, which is way more people estimated to have lived at the time, meaning your family tree at that depth contains the same people over and over. Of course your ancestry probably isn't uniformly distributed across the globe, but without modeling it mathematically my guess is that if you go back ~3700 years to when Abraham ostensibly lived you can find multiple people that appear in the ancestry of virtually everyone from the Old World.

Anyway intuition can often be poor when dealing with large numbers so if anyone has concrete math or research to share I'd be interested in being proven wrong.

> they all share many common ancestors, but that those common ancestors are probably shared by many others as well so it's not very unique.

That's my point. By "common ancestor" I meant, common ancestor common to them only. That's what I find to be unlikely.

And yes, you are right about this. There is plenty of vids on YT that explain the math

It is indefensible to make arguments of likelihoods without and understanding of context and priors. If I listed 1,000 people from around the world at random and claimed we all had a shared great^N grandfather (with N not so large at to be trivially true), I’d need some rather significant proof to back up at that claim, and barring that we could say it was unlikely to be true.

If on the other hand I consulted my family’s genealogical records that had been painstakingly maintained for generations, including only those matrilineal lines that are most solid to trace, and from that listed 1,000 folks who have the same grandfather, then my claim would not be very unlikely at all.

This case is much closer to the latter than the former.

Given the socio-historical relevance of family trees, genealogical records of anyone but the wealthiest are likely unreliable the farther you go back

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