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Comment by glofish | Hacker News Reader

I think there is a high chance that is 100% bullshit.

Most likely has to do with confusing cause-and-effect.

It could be just as well that highly methylated babies cry more and could be more demanding or parents with highly methylated babies are themselves less tolerant to crying thus end up handling babies more.

The problem, they way it is being reported, and they way it lines up with pseudo-scientific mumbo-jumbo groupthink makes it stink. That's why it is newsworthy. People want to believe that handling a baby will change their DNA.

Same bullshit like papers like this:

- Scientists Say They’ve Found a Code Beyond Genetics in DNA - https://www.nytimes.com/2006/07/25/science/25dna.html

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>I think there is a high chance that is 100% bullshit.

I haven't read the paper this article is based on, so I can't comment on the study or the reliability of the results.

However, epigentic effects related to the degree of maternal touch have been convincingly demonstrated in naked mole rats in crossover studies. I posted about this research previously. (https://news.ycombinator.com/item?id=18749285)

One thing that we know from decades of twin studies is that childhood family environment explains a vanishingly small percent of long-run adult outcomes.

Contextualizing this single study's result against the much larger, more established evidence from twin studies strongly suggests that one or more of the following is true.

- The results are spurious and won't replicate.

- The results are true, but the association is not causal, and is simply proxying correlation with an upstream factor.

- Lack of touch does lead to methylation in the short-term, but by adulthood there's strong reversion to the mean.

- The methylation has no significant impact on any actual metric that we care about like success, health, personality or wellbeing.

There are issues with twin studies, not the least of which the number of twins raised separately, but not adopted, is tiny. However adoptive parents are a small self-selected subset of the population.

It's not vanishingly tiny, simply small.

Can you think of a reason selection bias could be an issue, thus invalidating twin study cohorts?

Adoptive parents are people who have gone through a lot of effort and expense to get their children, so they're far more likely to be heavily invested in their kids. It's also expensive so they're likely to have money. If the effects of parenting are strong, but "cap out" -- i.e. above a certain level of care, parenting does little, but before that level it has a strong effect -- then twin studies will show little of that effect.

I'm not sure I follow the causality argument here.

A twin study should normalize everything genetically. Ergo epigenetic expression and environment are the only two causal levers. It sounds like you're arguing that parental involvement has a causal impact, which is the point of the studies to a degree.

Perhaps my original question was unclear: is there something the twins do or have done to them that cause a latent selection bias before adoption, thus invalidating the twin studies approach as a whole?

We are questioning how much the parenting has an affect on the child. The parents are self-selected and so are more likely to be similar to each other.

Agreed. That was my point. Not all twins under adoption are adopted, meaning there is nothing particularly invalidating about the twin study framework.

Most twin studies simply compare identical and fraternal twins in non-adopted households.

Since identical twins share twice the genetic covariance of fraternal twins, the impact of family environment can be backed out from the respective intra-pair correlation coefficients. In the limit case if genetics played no factor, then fraternal and identical twins should have identical pairwise correlations.

For example suppose pairs of identical twins have 45% pairwise correlation for adult IQ. And say fraternal twins have 25% correlation for the same measure. That would tell us that the population level variance of adult IQ is 40% attributable to genetic heritability, 5% to environmental heritability , and 55% to non-heritable factors (i.e. not genetics and not family environment).

In case you're interested, IQ is much more heritable than that for adults. The following quote is from Wikipedia:

"Twin studies of adult individuals have found a heritability of IQ between 57% and 73%[6] with the most recent studies showing heritability for IQ as high as 80%[7] and 86%.[8]. IQ goes from being weakly correlated with genetics, for children, to being strongly correlated with genetics for late teens and adults. "

Why would parents of twins pay much more attention to one than the other?

Maybe because, for whatever reason, one cries a lot more than the other?

But that would be an edge case. I would have assumed that identical twins behave similarly. How do they find enough neglected twins to make a reliable conclusion.

I’ve known three sets of identical twins. In each case the personalities were very different. Outgoing vs reserved, aggressive vs laid back, etc. I could easily see one wanting to be held more than the other.

Anecdotal, but... My (fraternal) twins have very distinct and different personalities. One requires an order of magnitude more attention than the other. We try to make up the difference, but it's hard.

Right, those studies can tell us about heritability, but cannot distinguish between common environment and genetics.

I don’t know. I have read this before. But this goes so much against my gut feeling and what I have experienced that it is hard to believe. It’s counter intuitive to say the least.

The documentary Three Identical Strangers also agrees with you, a fascinating account of triplets separated at birth to study parenting.

https://en.wikipedia.org/wiki/Three_Identical_Strangers

I'm not a professional scientist, but shouldn't the spirit of science be curiosity and exploration at all times, not shooting down a new idea as soon as you hear it?

If such an attitude were present in every person, science would not progress at all.

I'm not that long a veteran here, but I think at HN we are more interested in having our minds and ears open and feeling we can comfortably share and discuss articles that make us think, than fostering an attitude like this.

I mean this with respect, whoever you are.

I think that science works best if we marry two mindsets: the joy of seeing something novel, and the suspicion of seeing something too good to be true. They don’t have to be present in equal measure for every article, and while I wouldn’t word it the same way as the parent, I appreciate the healthy skepticism on this topic.

Yes: a good reasoner is charitable and critical. You need both.

That's great for a classroom setting, or in the lab, or wherever people are forming hypothesis. But in articles communicating research, accuracy matters. You can believe in the value of creative thinking and also want article that do a good job describing research.

This is about junk science - that is the true danger and bottleneck to science - that reward for making unsubstantiated but grandiose claims. These do far more damage than potentially unfair criticism.

I am a scientist by profession and I have come to believe that the majority of work in this field is wasted because people chase that 5-minute fame. Once you are in the field you can smell the stink a mile away.

It always sounds the same: "A second genetic code discovered", "Touch reflected in the DNA", "Next cure for cancer", "Scientists can edit now genes at high fidelity with CRISPR" all pure bullshit.

This article is terrible and did the grave disservice of not mentioning the work that has been done on this front using rats. Obviously, we cannot ethically reproduce the RCTs in humans to establish cause and effect, but there's sufficient evidence to form hypotheses and spur investigation in humans. I'm having trouble finding the exact primary literature that I wanted to cite just now, but here are a couple of things worth looking over:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2682215/

https://en.wikipedia.org/wiki/Michael_Meaney

scientific study: "The importance of touch in development", Brain Research Centre and Department of Psychology, University of British Columbia, Vancouver. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2865952/#__ffn_... (as commented elsewhere)

That study is only reference to the existing consensus, not the actual study from the OP.

I don't have the time to dig out the actual study but it looks like [1] it's originating in Canada (not NIH/USA) based on the publication of the press release.

Original comment of thread doesn't understand how much research is behind this idea (touch linked to higher outcomes long-term). I'd strongly recommend the commenter to read tribler's citation as that's scientific consensus at this point. If you want to read the recent study on DNA affects of touch, then below is that source of research.

1 - https://www.med.ubc.ca/news/holding-infants-or-not-can-leave...

I have performed DNA studies in my career. Measuring and interpreting methylation - understanding what it is, why, when and where it is present is at its infancy at best.

Sadly I have prime view how clickbaity ideas like this one drive most of the motivations behind investigations in life sciences.

It is not just this paper that is bullshit, the whole field of "epigenetics" that this paper is a representation of is bullshit as well - this paper is just one out of the long line.

As I pointed out it there is simply no proof that handling changes DNA. It could just as well handling stimulates the development rate which, in turn, also shows up as another signal.

The lie is not that A and B are present at the same time. The lie is presenting story as if A was caused by B. There is absolutely no evidence for that.

Now hundreds of scientists want a piece of the "cool" story, will jump headfirst into proving how LOVE will reflect in the DNA. No one will care about understanding what the heck is methylation - they will all be chasing baby handling and methylation. That's what I have seen happening and will keep happening thanks to papers like this.

> is at its infancy at best.

Hence why the main source is published with ~90 subjects studied. Science starts with one paper/experiment and builds from there.

> The lie is not that A and B are present at the same time. The lie is presenting story as if A was caused by B. There is absolutely no evidence for that.

That's not a lie. It's called a hypothesis. It's testable. They've tested it and encourage others to test as well.

I will tell you what they did. They collected data, with no hypothesis or any idea what they are looking for, then desperately fit various models until something showed up as statistically significant.

Of course, you could say: how dare you, how would you even know, ... I work in this field, the p-hacking, harking (hypothesizing after the results are known) is both pervasive and endemic. they massaged the factors, the genders, the ethnicity, the socioeconomic status etc until the model did something that was publishable.

It simply not possible to accurately correlate these two measures: self-reported minutes of touching a baby with the methylation levels of the DNA of that baby - if you are serious about accounting for all the possible variations across all factors

Your comments on this?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2682215/

A perfect example of what I am talking about. What is the final conclusion of that paper written in 2009!:

> Are the neuroendocrine effects of these experiences across the lifespan also mediated by DNA methylation? The answer to this question is not yet known.

So what happened in the following ten (!) years, have we finally figured out whether the effect is mediated by DNA methylation? Nah. Instead, they published another bullshit paper, this time about babies being held...

Ten years is (or rather should be) an eternity in science! The 1st smartphone was barely released back then - how far have gone in technology in this time? Yet we are nowhere closer to have proven or disproven the mechanism. Instead, they would much rather maintain the status quo and publish another bullshit paper.

Just a small caveat. When I quit my PhD (computational protein folding models) in 1987, it was because I didn't want to spend 10 years working on a problem and getting nowhere. Turned out I was wrong - way too optimistic!

Until the recent ML-based announcement from Google (and maybe not even with that in hand), protein folding research went nowhere for at least 30 years. So I wouldn't be too critical of a 10 year gap.

most certainly, I would fully agree that touch is an important ingredient to socialization and stimulation -

it is the premature claim that it changes DNA what is so annoying and misleading.

because once something changes your DNA it suggests that it is there forever (that is why it captures people's imagination)

Not if it is the methylation of DNA, modulating the expression of that DNA...methylation is frequently modulated by experience.

I think they forgot to say being more touched probably means parents are more close by, more caring. Why would you not touch a baby if you are constantly close by? So probably not BS, just a study say is right, but not for all the right reasons.

To add to that, there are so many problems with self-reported studies.

> They also asked parents to keep track of how long and how often they gave care to their child that involved physical contact, according to a press release.

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