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Comment by YetAnotherNick | Hacker News Reader

Genes describe lot of things from obese tendency to height to IQ to your looks. If someone has an IQ of 70, there are very likely to live a difficult life. Yes IQ is not intelligence you will say but still there is a limit to everyday functioning if someone's IQ is low. Ask a conventional ugly person(specially female) about their life.

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Hard cases make bad law. In other words basing our precedents and rules on extreme cases is not a good idea.

While extreme cases are useful for illustration and thought experiments, they are quite distracting when the real issue is small variances in the top ranges of ability.

> from obese tendency

Which should make you rather skeptical of inferring just how innate IQ really is (assuming it's a valid concept).

The heritability correlations for obesity are only slightly weaker than IQ. Yet we know for a fact the logical complexity of losing weight is simple (doesn't mean it's easy). Anyone can and people do lose weight, even if statistically it may be rather unlikely.

It's completely plausible to me that intelligence can be simple but hard to increase too.

If it's not a statistical anomaly and the genes truly do contribute to obesity, the causation must be very indirect and situational.

Not to mention, obesity has increased by an order of magnitude in 50 years, with no signs of stopping. It's actually a nice example of how little genetic variance can actually matter at the population level, especially since it is a much more objective measure than IQ tests.

Every phenomenon has both sides. While many people grew obese, there are still significant outliers among us who chug beer, consume current obesogenic diet and stay slim.

Is it genetics? Is it gut microbiota? (E.g. genetics of other species?)

> Is it genetics? Is it gut microbiota? (E.g. genetics of other species?)

If you don't control for portion size comparing people who all have a burger and fries for dinner every night is basically useless, those meals could be hugely different in composition, portion size or how much is left over. Even if dinners are identical, snacking can be thousands of calories a day that you might never see happening. You've also missed what activity they do as well...

Two people who both "chug beer and eat greasy takeaways" whenever you see them out can be very different the rest of the time. If one stays slim and one doesn't it's far more likely to be that the former eats smaller portions overall, snacks less between foods and does more activity overall, before reaching for more exotic answers.

Portion size is notoriously hard to control for in freely moving people. If people self-report their foods, they are likely to make mistakes.

I know of one study only where the numbers can be trusted, and it was done on prisoners, where every single gram of food that passed their lips was accounted for. They were fed the same diets, but their weight gains varied a lot:

https://dm5migu4zj3pb.cloudfront.net/manuscripts/106000/1065...

The only place you can see weight gains is by looking at Table I and working it out yourself for each subject, and only the last subject PW had an outlying weight gain in absolute terms but his starting weight was also an outlier - his relative gain was the same as all the others as well.

The paper is about how the weight of fat cells changed at different subject weights, not how much subject weight changed for a fixed food size - the only mention of food portions is with respect to ensuring weight was maintained, gained and lost for the different stages. "After desired or maximum obtainable weight was reached" indicates they weren't using weight as the outcome here.

The only place you can see the weight gains is by looking at Table I and working it out yourself for each subject, and the relative gains are all very similar: 23.3%, 25.3%, 21.4%, 20.0% and 18.0%. I'm guessing they wanted them to put on 20-25% of their body weight to give consistent and measurable changes to the fat cells.

Obesity among US adults has gone from 10-15% in the 60s to 40% now. It's extremely unlikely that genetics changed in 60 years, but environmentals did.

I understand that some have genetics that make it harder for them to keep off weight, either by metabolism, neural hunger stimuli or otherwise, but then we're still back to the fact that environmental changes made the biggest effect, not genetics. Why can't this be the case in your other examples too?

TL;DR: Yes, genetics matter. What's more relevant is, how much?

>It's extremely unlikely that genetics changed in 60 years, but environmentals did.

Due to epigenetics, environmentals actually shape genetics to a degree.

Epigenetics does not change your DNA or what you pass down to your children, and is reversible, so I wouldn't call that "shaping genetics", at least not in the way I was referring to.

Heritable epigenetics is a (very cool) thing, though apparently somewhat overblown.

But epigenetic changes during foetal development could effect the likelihood of being successful at passing ones genes along at all, although I've no idea how you'd manage to isolate or replicate these effects in any scientifically useful fashion.

Someone in these discussions always brings up epigenetics at some point, its impact there far exceeding its impact on population genetics I would guess :) Nobody ever talks about genetic drift or gene flow however, probably because despite being actual things that affect population genetics talking about "nearly neutral drift in small populations" is really hard to wedge into an ideological shouting match dressed up as a scientific debate.

I've always viewed genetics and talent as essentially your maximum potential. Lots of ways to drag you down from being all that you can be (lead, malnutrition, a good knock on the head), but given a sufficiently good environment, genetics (or perhaps inherent ability might be better) then become the limiting factor on how far you can go.

Your random guy on the street ain't going to be Newton, no matter how much he studies or loves math. Similarly, the man born with muscular dystrophy isn't going to be setting marathon records.

This is a simplification of course, but I hope it conveys the point.

You can't discount environment either.

We have fat raccoons, that implies that genetics doesn't matter as much as we think we does.

Same with intelligence, how much is it genetics and how much is that the environment doesn't promote desired traits.

I agree with you, but an IQ of 70 is mentally disabled, so it's not really a good example of "bad" genetics, so much as it is an example of a disability.

That seems like a strange line to draw, surely plenty of disabilities are genetic, implying bad genetics no?

Sure, but it's unlikely that you would have an IQ that low, and not have a specific medical disorder that is causing some of your impairment. E.g, Down Syndrome is a chromosomal change, something that can be measured outside of a 'bad genetics'.

What? You somehow think that if there is a named thing then it's not genetics. It's genetics both if it's a named thing, and if it's yet unnamed thing too.

My point is that the distinction is important.

Of course, named disorder or not, genetics can be the cause/have a high impact.

There is a thin line between disability and just different genetics.

E.g. is it bad for a primate to have bad bite strength? What if that disability enhances their thinking ability (by both allowing their brain to expand more since the muscles holding the jaw are weaker and by forcing them to use something other than their bite strength)?

Isn't that a rather arbitrary distinction? Feels you are making it easy for yourself to just dismiss a certain amount of "not-normal" people as not relevant to the discussion? So, what do you define as "bad genetics", then?

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