Humans evolved to tolerate smoke poisoning [pdf]

https://www.gwern.net/docs/genetics/2016-hubbard.pdf

by gwern • 9 years ago

70 46 9 years ago

pcrh• 9 years ago

This is interesting. I wonder if the tolerance of the mouth to heat (relative to other areas with a thin epidermis) is also related to cooking.

VeejayRampay2• 9 years ago

The way the title is phrased is strange. To the young/uneducated reader (not so many around here, but still), it reads like humans evolve to develop a particular trait, when we know that people who developed that trait got an evolutionary advantage and ended up spreading their DNA more than others on average.

Not as catchy a title, sure, but at least, it doesn't misrepresent the evolutionary process.

NOTE: I am not an evolutionary biologist, so there is most likely an even better way to rephrase my rephrasing. I'd be glad for anyone to do so, the more accurate, the better.

posterboy• 9 years ago

it reads like humans evolve to develop a particular trait, when we know that people who developed that trait got an

people who developed that trait had to evolve to do so, no? Not as an entire population, but maybe over the live span of individuals.

Maybe the smoke itself caused that, as exposure often does, "evolving" in some individuals who then pass immunity markers down over generations through blood in the womb rather than genetically. Or maybe the smoke is cancerous and caused beneficial mutations. I should read the paper (edit: it says genetic). All I'm trying to say is, either development is subsumed under evolution.

inimino4• 9 years ago

people who developed that trait had to evolve to do so, no?

The word "evolve" in English means a gradual change, so no.

Random genetic mutation isn't a response to the smoke, and there isn't anybody born unadapted who then adapts by exposure. The species evolves, individuals don't.

logfromblammo4• 9 years ago

Evolution occurs via reproduction over the span of many generations. Individual adaptation on a single-lifespan scale occurs via epigenetic methylation tagging of the existing (evolved) genome.

You cannot become better adapted to smoke unless your genome already contains a gene that mitigates the damage, or a gene that can regulate expression of a damage-mitigating gene based on that specific stimulus.

So if you breathe smoke frequently over your lifespan, you may have a gene related to mucus in the lungs expressing its protein at maximum capacity 24-7, while someone who never breathes smoke has that gene "turned off" most of the time.

Transfer of individual adaptations, usually in the form of antibodies that can teach immune cells to respond to a specific hazard, is very limited, and will only last as long as that specific threat is continuously endemic. We have mostly supplanted that natural capacity with artificial vaccinations.

Random mutations are usually harmful. Sexual reproduction and selection is the mechanism to shuffle the most harmful mutations out of the genome while still retaining the rare beneficial mutation. If the mutation rate is too low, the species cannot evolve quickly enough in changing environments. If the mutation rate is too high, sexual reproduction cannot eliminate the bad mutations fast enough.

patrickg_zill• 9 years ago

I think you are saying that there is no teleology in the theory of evolution.

inimino4• 9 years ago

humans evolve to develop a particular trait
people who developed that trait got an evolutionary advantage and ended up spreading their DNA more than others on average.

The first is shorthand for the second.

VeejayRampay2• 9 years ago

Ah OK, my bad then.

iand• 9 years ago

It's sloppy shorthand though because it can be (deliberately) misconstrued to suggest agency and directional purpose.

fsloth• 9 years ago

" Our findings reveal that a functionally significant change in the AHR occurred uniquely in humans, relative to other primates, that would attenuate the response to many environmental pollutants, including chemicals present in smoke from fire use during cooking. "

So we have some genetic tolerance to bad stuff created from cooking? Cool.

This does, however, raise ever more questions about studying the effects of chemicals on rats and primates and drawing conclusions from that to human populations.

Bartweiss3• 9 years ago

This seems like a really good question to raise, and I'm embarrassed that I didn't think of it at all. I know carcinogen studies are already touchy since cancer risks vary so wildly, but this is a nice reminder that even within primates you get this kind of problem.

a_bonobo2• 9 years ago

I don't buy the smoke poisoning angle.

They compared with Neandertal AHRs and found that human AHRs may have undergone selective pressures since they're quite different, so the authors tried to connect these changes with the invention of fire. However AHRs bind to many things.

Also, Neandertals also used fire extensively (see for example http://www.pnas.org/content/108/13/5209 ) so they should have undergone the same selective pressures, so they should have the same or similar changes as humans?

AimHere• 9 years ago

Might the selection pressure have been fire related, without necessarily being just the use of fire?

If, for one speculative example, Neanderthals mostly used fire outdoors, while modern humans used it indoors with correspondingly thicker smoke concentrations, wouldn't that account for the difference? Or perhaps only a few Neanderthals out of any given population used it regularly (for crafting tools, say), while almost all modern humans could have used it for cooking food.

a_bonobo2• 9 years ago

I see! But that's a bit hard to prove, isn't it? I don't think we have enough archaeological sites with proven fire places to prove that assumption

Houshalter• 9 years ago

Smoke still is bad for humans though, see this essay: https://www.samharris.org/blog/item/the-fireplace-delusion/

There is no amount of wood smoke that is good to breathe. It is at least as bad for you as cigarette smoke, and probably much worse. (One study found it to be 30 times more potent a carcinogen.) The smoke from an ordinary wood fire contains hundreds of compounds known to be carcinogenic, mutagenic, teratogenic, and irritating to the respiratory system. Most of the particles generated by burning wood are smaller than one micron—a size believed to be most damaging to our lungs. In fact, these particles are so fine that they can evade our mucociliary defenses and travel directly into the bloodstream, posing a risk to the heart. Particles this size also resist gravitational settling, remaining airborne for weeks at a time.
Once they have exited your chimney, the toxic gases (e.g. benzene) and particles that make up smoke freely pass back into your home and into the homes of others. (Research shows that nearly 70 percent of chimney smoke reenters nearby buildings.) Children who live in homes with active fireplaces or woodstoves, or in areas where wood burning is common, suffer a higher incidence of asthma, cough, bronchitis, nocturnal awakening, and compromised lung function. Among adults, wood burning is associated with more-frequent emergency room visits and hospital admissions for respiratory illness, along with increased mortality from heart attacks. The inhalation of wood smoke, even at relatively low levels, alters pulmonary immune function, leading to a greater susceptibility to colds, flus, and other respiratory infections. All these effects are borne disproportionately by children and the elderly.
In the developing world, the burning of solid fuel in the home is a genuine scourge, second only to poor sanitation as an environmental health risk. In 2000, the World Health Organization estimated that it caused nearly 2 million premature deaths each year—considerably more than were caused by traffic accidents.

raverbashing• 9 years ago

Of course it's not good

But if your options are, stay close to the fire or die, that's an important selective pressure

hvidgaard2• 9 years ago

I'm sure there is some truth to the article, but it paints a very different picture than the referenced paper at the buttom.

Finally, returning to the questions posed at the start, we conclude that although there is a large and growing body of evidence linking exposure to wood/biomass smoke itself with both acute and chronic illness, there is insufficient evidence at present to support regulating it separately from its individual components, especially fine particulate matter. In addition, there is insufficient evidence at present to conclude that woodsmoke particles are significantly less or more damaging to health than general ambient fine particles.
Nevertheless, given the importance of woodsmoke as a contributor to particle concentrations in many locations, strategies to reduce woodsmoke emissions may be an effective means of lowering particle exposures. In addition, given the weight of toxicologic evidence, additional epidemiologic studies are needed to confirm our conclusions.

Bartweiss3• 9 years ago

Wow, thanks for following through there.

As much as I complain that sloppy research oversells its conclusions, I tend to forget how often reporters will take a good paper and simply skip all the lines like "not significant" and "no causation" that stand in the way of an exciting article.

schiffern3• 9 years ago

In 2000, the World Health Organization estimated that it caused nearly 2 million premature deaths each year—considerably more than were caused by traffic accidents.

Everyone is rallying around autonomous cars to decrease unnecessary deaths (and rightfully so), but relatively few folks are familiar with rocket stove technology.

https://richsoil.com/rocket-stove-mass-heater.jsp

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

Releasing smoke is energy inefficient, since it's literally unburnt fuel! Considering the fuel savings, the lifetime cost of switching can be negative in some cases.

In terms of cost per statistical life saved, it's an extremely compelling technology.

Retric• 9 years ago

Solar hot water heaters are vastly more convenient and generally cheap. But, rocket stoves are great for rarely used structures, cooking, or the far north.

blackguardx• 9 years ago

Thanks for sharing those links. It looks like it would be hard to start the rocket action correctly. You would have to preheat the circulator "chimney" somehow. Until then, smoke would pour into your house.

This is a problem with normal wood-burning cooking stoves as well. Smoke doesn't go into the chimney until you establish a convection draft or the wind creates a venturi effect.

hvidgaard2• 9 years ago

It's the same with a mass oven. It has several burn chambers that is designed exactly yo burn all smoke. Heck, I even have a portable stove that uses secondary combustion to burn all the wood and smoke. If I ever have to buy a wood stove, I want one which is designed to burn it all. I probably even go all in with a mass oven.

Neliquat• 9 years ago

Try telling that to my idiot hippie neighbors who drive a prius and have weekly bonfires.

sdfin• 9 years ago

A bonfire's smoke moves in the wind's direction. If they sit towards the bonfire with the wind in their backs, what's wrong with that? Although if the smoke goes toward your home I understand you anger.

autotypo• 9 years ago

Why not tell them yourself? Passive aggression on a news feed won't improve the situation.

On the other hand, if the neighbors are burning wet wood, pine or otherwise Doing It Wrong maybe they would appreciate a friendly heads up.

logfromblammo4• 9 years ago

Why not help them build a Dakota fire pit?

It's essentially just a big hole with an air intake tunnel, so that fires in the pit combust more completely, with a very significant reduction in smoke and particulates.

You probably can't do anything about them being ideologically inconsistent with respect to burned fuels as an energy source, but you can reduce their impact on yourself and your mutual neighbors.

wtbob• 9 years ago

There is no amount of wood smoke that is good to breathe. It is at least as bad for you as cigarette smoke, and probably much worse.

And yet very few sane people wish to ban wood smoke. It smells good. There's nothing like the smell of fall and winter, with fragrant smoke blanketing the countryside.

I'm perfectly aware that wood smoke is bad for me, that it pollutes my lungs and makes my food poisonous. But it's delicious.

bougiefever• 9 years ago

I don't smoke, but I am a beekeeper, so I am often breathing in smoke. I've always worried a little if that was bad for me. I guess I will try harder not to breathe it in. Without it, I would get many more stings, which I assume is also not good. There is a chemical replacement for smoke, but that is probably even worse.

Dowwie• 9 years ago

Lung cancer?

belorn• 9 years ago

Reminds me of a story where Robert Sapolsky, a professor in biology when he was staying in a native African hut and decided to put out the indoor fire before sleeping, since he was concerned about the smoke. Later during the night he woke up, covered in driver ants, realizing very fast the reason why the natives sleep with the huts full of smoke.

detritus• 9 years ago

I've often wondered whether something similar might be at play in relation to the supposed cancer risks from acrylamides forming in burnt food. Sure, the stuff's poisonous to rats etc, but given our physiology has evolved smaller intestinal tracts and larger brains in relation to cooked foods (particularly, meat), might it also be that we're less susceptible to its cancerous potential than other mammals?

Humans evolved to tolerate smoke poisoning [pdf]

Related Stories