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Comment by supernova87a | Hacker News Reader

To what extent do genes encode the facial features that make them distinctly recognizable to us? Is there a way to say it as a "%"?

I can certainly see how your basic head size/shape and position of nose/mouth/eyes, etc is baked in there somehow.

But I'd love to know, the fundamentals of why you look like your parents, what is that? Certain (75%?) placement of facial features locked in by genes, so of course you look like them, but then the last 25% up to developmental noise? (Example -- fingerprints, almost completely determined by developmental noise, right?)

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Identical twins, sharing the same DNA, look rather identical but not truly identical. Even when raised apart.

I am skeptical of reconstructing faces from DNA using current knowledge and technology though. It seems theoretically feasible, but I wouldn't bet on this company being able to do it well.

Developmental noise will be dominated by fetal development, not life after birth.

Maybe so, but fathers can look a great deal like sons and they only share something like half their code and don't share a womb at all. Identical twins share their code and look even more alike.

I think later life matters like obesity probably make a bigger difference. Being fat or gaunt can dramatically change somebody's appearance. Grooming habits as well. Spies deliberately adopting disguises can make themselves look quite different by modifying these sort of things.

Which probably isn’t directly encoded into your dna, but rather epigenetic markers which may or may not be easily collected and quantified.

Not necessarily. Fitness, sun, sleep, alcohol, drugs, diet, smoking, and stress are some examples of environmental factors that can influence your appearance including your face after birth.

If you were looking for a suspect and the only identification you had was a photo of their identical twin, would you use it?

Obviously it's not a perfect match, but it's going to be wildly better than a sketch artist's attempt at a usable drawing.

This assumes that the company is able to produce an accurate image that's on par with a photo of the subject's twin, when it's entirely possible that the images the company produces are no more accurate than noise.

Oh for sure, I fully agree. However, is this company's tech actually that good? It would be interesting to see how well it does with the DNA of real twins; how close can they actually get compared to two people with the same DNA? Could it make a face that really looks like their triplet?

Unfortunately the article doesn't have any comparison images of any sort, so it's hard to evaluate. But the skeptical/cynical part of me suspects the article would contain such comparisons if it worked well.

See https://news.ycombinator.com/item?id=24457194 for examples.

Huh. Not great... but credit where credit is due, some of those are much better than I expected.

Yeah. In fact, the least I would expect from this article are some samples of "real/reconstructed", but as normally expected from journalists it is just a lot of words talking about some "controversy" and non-descriptive anecdotal poorly written detective stories instead of something of value.

It's pretty much a rule that if you're writing an article about something visual, you don't include any images.

Unless you have some deforming disease, accident or malnutrition, identical twins have very close to identical faces.

Identical twins have very similar, but distinguishable fingerprints.

Identical twins having extremely similar faces isn’t exactly a great argument for determining facial characteristics via dna, as identical twins also shared the same environment during fetal growth. It’s entirely possible that genetics and developmental experience combined creates facial structure, and that dna alone is insufficient.

I guess you should compare to non-identical twins. Who I think look like siblings who happen to be the same age. But no doubt someone somewhere has tried to quantify this.

Fair point.

The only experimental way I can think of checking this is how similar cloned animals are.

A quick googling seems to say clones are quite similar, but not really identical. Which I think somewhat contradicts my claim.

I think "deforming accident" is a lot easier than some might realize. I personally have had an injury that probably changed the shape of my face, and it wasn't super note-worthy. Especially if someone gets something like a broken jaw, you can look almost unrecognizable.

Depending on how you breathe, your posture, how you sit, if you exercised consistently as a child, etc. your face can look completely different. The greatest example of this is how early humans had significantly larger jaws due to their diet and exercise, while humans today who have almost the exact same facial genes have much smaller jaws.

The introduction of the fork in the middle ages caused the development of the overbite. https://www.theatlantic.com/health/archive/2013/01/how-forks...

Also: sanitation gave us polio: https://nextnature.net/2014/01/how-modern-sanitation-gave-us...

Do you have more reading on that? Especially on the breathing and posture/sitting part.

Would identical twins suggest the genes encode facial features to a high degree?

No, as identical twins also share whatever happened in utero.

To draw a strong example, take fetal alcohol syndrome, which often causes facial changes. Two identical twins with FAS will share similar facial changes, but these changes will not actually be encoded in their dna, but instead will be the result of developmental history.

You keep repeating that DNA doesn't have a strong role in determining what a person looks like. Yet everything we know about development including twin-studies seems to suggest that in fact it has strong role.

For example, this scientific article published in Nature opens with this:

"The human face is a complex trait under strong genetic control, as evidenced by the striking visual similarity between twins."

https://www.nature.com/articles/srep45885

These researchers who are _specialists_ on this field have no doubt. Why do you keep casting doubt on this?

Clones from the Dolly sheep were not identical. If I remember correctly it is thought that epigenetics played a role in their differences.

Yes, it depends on the facial feature, but some parts are fairly highly heritable.

https://www.nature.com/articles/srep45885

Probably pretty predictive. Identical twins have different (but correlated) developmental noise and look anything from very similar to totally identical.

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