Humans evolved to tolerate smoke poisoning [pdf]
gwern.net
gwern.net
>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.
But if your options are, stay close to the fire or die, that's an important selective pressure
> 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.
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.
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.
To that list of rocket stove applications & advantages would add backup heat for solar hot water, accessible to developing countries and the poor, and (when built from masonry) ease of construction in the charred afterscape. I'm kidding of course on that last one. Mostly. ;)
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.
Smoke free startup is an important design/operational consideration. There are lots of videos demonstrating startup technique (search "rocket stove starting"). Here's a couple good ones: https://www.youtube.com/watch?v=Ls_eqNB6d0Y&t=1m23s https://www.youtube.com/watch?v=aSkUquOQt5w
Note that the goal of the drafting chimney is not to soak up a lot of heat, but rather to be insulated and have low thermal mass to minimize heat loss. The higher the air exit temperature from the riser, the stronger the draft. The important thing for self-drafting is to heat the air in the riser, and only secondarily heat the riser material itself.
A good design should make startup as "idiot proof" as possible. I've seen a few builds that use a 12V case fan on the air intake. Since the goal is to heat up the air in the riser (and that heating the riser... draws hot air into the riser), all you have to do is "tip it over" into that stable equilibrium.
Imo there's a market opportunity for an inexpensive, compact, nice looking, and easy to operate rocket stove. The open source (and excellently documented) "batch rocket" design seems a good place to start. http://batchrocket.eu/en/
From the article up there I get the sense that wood fires inflict a lot of particulates even when you can't smell smoke, but open-air fires are still way safer (on this level) than in-home ones.
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.
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.
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.
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?
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.
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.
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.
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.
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.
You are made of cells that are many generations separated from the fertilized egg. I don't see why you accept evolution at the species level but not cell level.
This sounds like a kind of reverse creationism, where macro-evolution is ok but micro-evolution is not.
Are you denying this can happen? Or is it that you do not consider that process to be evolution?
The number of random mutations necessary to produce one lung cell that is better adapted to smoke inhalation is large enough that the entire remainder of the lung already has carcinogenic mutations.
Sexual reproduction is a mechanism to eliminate harmful mutations without discarding the occasional beneficial mutation.
It is not necessary for that purpose, but it is sufficient. Humans are now technically capable of identifying a potentially beneficial genetic mutation, and inserting it into an unrelated person's genome. It is, however, more likely that the protein result of the mutation will be used to research and develop a pharmaceutical drug or medical procedure that replicates the beneficial effects of the mutation.
In short, the probability of you spontaneously developing an adaptive mutation in a non-germline cell is absolutely infinitesimal in comparison to the probability that someone in the last 10000 generations of your ancestors developed such a mutation when producing a sperm or egg cell and passed it along to you.
> "The vast majority of random mutations are harmful."
- You sure they aren't "neutral"?
> "The number of random mutations necessary to produce one lung cell that is better adapted to smoke inhalation is large enough that the entire remainder of the lung already has carcinogenic mutations."
- No, in principle it can be a single point mutation to a promoter that increases affinity for a transcription factor.
> "Sexual reproduction is a mechanism to eliminate harmful mutations without discarding the occasional beneficial mutation."
- So are apotosis and immune surveillance.
> "Humans are now technically capable of identifying a potentially beneficial genetic mutation, and inserting it into an unrelated person's genome."
- No, they aren't. They modify and select cells in a dish, not in a person.
> "It is, however, more likely that the protein result of the mutation will be used to research and develop a pharmaceutical drug or medical procedure that replicates the beneficial effects of the mutation."
- Ok, I am just including this for completeness sake.
> "In short, the probability of you spontaneously developing an adaptive mutation in a non-germline cell is absolutely infinitesimal in comparison to the probability that someone in the last 10000 generations of your ancestors developed such a mutation when producing a sperm or egg cell and passed it along to you."
- You are talking of 10^4 fertilized eggs vs 10^13 cells in my body[1]. I'm not sure how many divisions it is from egg to egg, but it has to be less than the 10^16 supposed to happen during the human life span[2].
Actually I am pretty sure I have read somewhere that the human body probably contains at least one cell that has a mutation at any given bp. I will see if there is time to find it later.
[1] https://www.ncbi.nlm.nih.gov/pubmed/23829164
[2] http://bionumbers.hms.harvard.edu/bionumber.aspx?id=100379
If one cell in your body mutates such that it might protect your lungs against damage from smoke inhalation, it won't do you any good (nor ill, probably) if that cell is in your toenail matrix.
Nor do all cells in the body divide at a uniform rate.
I would guess that the one type of cell most likely to show an effect from non-germline mutation are the hematopoietic stem cells. They produce all types of blood cell, are self-renewing, and blood cells touch every other part of the body. But they are also only 1/10000th of all myeloid cells. There may be only 10^6 HSCs in one body
Your reference [1] only included the abstract: https://www.researchgate.net/publication/248399628_An_estima...
Also, 10000 generations of ancestors is not 10^4 fertilized eggs. Most people have two parents. 0 generations of ancestors is 1 fertilized egg. 1 generation is 3. 2 generations is 7. 3 generations is 15. The upper limit on N generations is 2^(N+1)-1 fertilized eggs. For 10000 generations, that is 4e3010 cells. Though the number of individuals in the species eventually limits that number, as multiple inheritance causes some of your ancestors to be counted more than once. The lower limit would be the degenerate case where all 10000 generations were siblings that had at least one son and one daughter, and that is 2e4. So quite a lot of room for variability in there.
Knowing that rate in the various tissues even to within a few orders of magnitude is the holy grail.
(By the way, you didn't mention the most common way that lung cells mutate in a smoky environment and begin to divide more often.)
Evolution involves random mutations and the filter of natural selection. The process you're describing doesn't participate in the filter, and random mutation alone gets you vastly more downside than upside. The only reason evolution works is because of the filter which lets us keep the upside in the gene pool while the downsides are filtered out.
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.
> 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.