Head lice transmit to new hosts when people lean their heads together. Humans frequently touch their heads to express friendship or love, while this behaviour is absent in apes. We hypothesize that this behaviour was adaptive because it enabled people to acquire head lice infestations as early as possible to provoke an immune response effective against both head lice and body lice throughout the subsequent periods of their life. This cross-immunity could provide some defence against the body-louse-borne lethal diseases like epidemic typhus, trench fever, relapsing fever and the classical plague. Thus the human ‘touching heads’ behaviour probably acts as an inherent and unconscious ‘vaccination’ against body lice to reduce the threat exposed by the pathogens they may transmit. Recently, the eradication of body louse-borne diseases rendered the transmission of head lice a maladaptive, though still widespread, behaviour in developed societies
Now hear me out, obviously you don't want your child to be sickly, but is there a certain level of sickness that it's actually good to allow nature to inflict on your child? Chicken pox parties, for instance, are a thing, and for a kind of good reason - chickenpox is far milder for children than it is for adults. Sure, the virus never really leaves you and you might get shingles later in life when your immune system craps the bed, but it's stupid to have the notion you'll be able to quarantine your kids from chickenpox their entire lives. Not even the Atlantic Ocean was able to permanently quarantine people against chickenpox, and when it failed millions of people died. Granted, many more diseases are MORE harsh on children than adults and vaccines exist, but I address these later in these posts (I'm not saying vaccines don't work either, since the ones that work clearly do).
Human beings co-evolve with our pathogens just like we co-evolve with our gut flora. When human beings get a disease the response is not to quarantine indefinitely until the disease dies out, but to actually get it. Diseases that die out or don't circulate much do so because they're diseases that are bad at spreading, not because people are all that capable of staying away from people bleeding out of their eye sockets for two seconds. The effects of the disease might be really really bad, but that just prompts stronger human adaptation in response to the disease. Look at sickle cell, oval cell, thalassemia (common among Mediterraneans!) in response to Malaria, which kills a lot of people in the tropics. Getting the genes for sickle cell homozygously is life-ruining and probably killed most kids which had it until recently I'm guessing, but the genes were still selected for because human beings were forced to co-evolve with pathogens and evolution is throwing shit at the wall and seeing what sticks. Hell, it's common for animal species to have a different parasite burden between the sexes, is having and dealing with parasites and diseases not part of the billion base pair-long plan?
Removing pathogens and parasites can even have negative effects because the immune system is so used to dealing with a constant load of them. Intestinal nematodes have been used to treat autoimmune disorders. You can't just have an entirely sterile environment, that will fuck you up. The immune system must exist and it must be constantly doing shit, without an immune system you die to fungi in the air like AIDS patients, you rot like a piece of dead meat in the sun, your immune system is keeping you from being eaten alive by a billion tiny organisms. It's NORMAL to be sick. It's NORMAL to have parasites. When I was a kid and I shit worms out of my itchy bumhole I freaked out, but I've never gotten sick in the past 10 years so I think I'm right. Likewise the scientists in the above paper are theorising that one of the reasons touching heads together wasn't totally maladaptive was because infesting people with head lice helped prime their immune systems to deal with the body lice which were pretty ubiquitous in clothing until recently. When have nits ever hurt a kid anyway?
If vaccinations were really some magic bullet miracle cure, why did the mortality from all the diseases they were supposed to treat (even ones they eradicated, like smallpox!) drastically decrease way before their introduction to the population simply because people figured out modern-style hygiene and nutrition? They're not the full picture of epidemiology throughout history, far from it. I was reading about the conditions of male and female convicts shipped to Australia, and in those days Germ theory was something kind of out there people debated. Plus, because it was convicts, they didn't really care and gave them foul water from the Thames to drink. Obviously, this killed a lot of people. Through lack of understanding and lack of care to change it most of the human race lived in utter squalor and filth until pretty recently. Imagine hopping in a time machine to 300 years back, not long after the conclusion of the War of the Spanish Succession, to see the European royalty that you see nice portraits of on Wikipedia. Mon dieu! They all smell like poop and their clothes are full of lice! Their unventilated palaces are even filthier than the average contemporary rural cabin, and many courts regularly travel in part because having so many people in one place causes a massive accumulation of filth. The poor, underfed, overworked, illiterate, living in shitty (literally) slums and shacks with no ability to protect themselves against infectious disease even if they had the knowledge, get sick. It's no surprise that fixing THIS was the main cause of a massive reduction in mortality from diseases after the industrial revolution.
But are now we too clean? Are we too sterile? Our autoimmune disease record seems to suggest we might be. There's also definitely a genetic angle. Does reducing infant mortality from 1/3 under 5 and 1/2 under 16 (pretty constant for most of history, from early modern England to 100 AD Mexico) to virtually zero in the blink of an evolutionary eye seriously have no effects on the innate ability of human beings to resist disease, among other things? If sickly children who demonstrably grow up into shitty neurotic adults with health problems die of some disease a healthy young lad gets over perfectly fine, what is the problem with the sickly child dying? I am not suggesting we kill people, simply that nature take its course on individuals for whom deleterious mutations have unfortunately compounded to the extent that many people alive today in Western countries would not be able to survive to adulthood and give natural childbirth in less enlightened, clean times. Thanks, Semmelweis! Should we be shocked this is all the case? This is how the bulk of natural selection works, most mutations are aberrations which have to be pruned from the continually-growing tree of life through God's intervention in the form of disease and hunger. If children who cannot even survive a disease as pissweak as measles die of it, should we endlessly cry over it? The Romans, for whom the "dull" smell of the unbathed poor as they described it must have been a common reminder of how filthy their environment was (still superior to Europe until the early modern era!) were advised not to mourn the death of an infant until it had "cut its teeth". Many cultures did not even name their offspring until they could be sure they would survive.
You might go hey, this sounds like some Hitler eugenics stuff! To which I shall respond, no, not really!
Adolf Hitler in Mein Kampf advocated for the race having as many children as possible, for the purposes of those children being born into a world of struggle so that the best stock of the race could be selected for. Hitler's world was fresh out of a preindustrial world, in which the wealthy and more intelligent actually outbred the poor and flushed out their gene pool several times over with downwardly mobile offspring. Currently, due to how easy living and surviving is, the opposite is happening. The sick, the parasitic, the useless, the slow are allowed to proliferate on the taxpayer's dime. This is demonstrable when looking at who breeds in Western countries, looking at IQ (general intelligence is fairly strongly correlated with life outcomes, SAT scores et cetera and is pretty heritable along with having good predictive validity), being on welfare or criminal background. These people probably have surpassed a crucial and tragic threshold of compounding mutational load. Researchers have asked whether the declining paternal age in modern times has been enough to assuage this and the answer is nah, it's grim. Obviously smart people are not automatically resistant to diseases, but my point is there is nothing eugenic about modern fertility trends.
For this reason, you might be pleased to know I actually disagree with Hitler's take here. Looking at GWASes vs genetic studies on just about any polygenic trait, I honestly think that the human genome is far too complex (not just the genes themselves but the way all of the genes interact with one another and the different molecules they produce interact with each other in the human body, what is and isn't "junk" DNA, etc) for any state authority to realistically be able to control the genetic quality of its population in the long term. Industrialisation will inevitably cause the rot of the human quality of a population even if you have kooky programs like lebensborn, sterilisatons, welfare and medals for german mothers, abortions, CRISPR etc in place. Such a complex system with so many variables that is so interconnected with everything around it and so many individuals is outside the scope of rational human control, especially in the long term over many generations which is what actually matters for evolution. If it were hypothetically technically feasible for us to precisely institute eugenics rather than just "encourage good breeding" (which in the long-enough term in an industrial society is impossible), it would obviously end very badly since the development of large complex systems over long periods of time such as societies is out of rational human control, the inertia of a technological society is far stronger than any aspirations for freedom and human dignity, and it would be advantageous for societies to compete with each other by producing progressively more docile, compliant husks of human beings in something akin to Huxley's Brave New World. Even the Third Reich, with its Darwinistic logic, would eventually decay and fall to such a thing. It wouldn't just be humans, either. Not just our crops and animals, either. The best way to keep the Earth as healthy and productive as possible with an effectively complete (for all intents and purposes) understanding of the natural sciences would be to turn every organism into a tailor-made product of the system. Take, for example, the recent insertion of wheat-genes for oxalate oxidase into American Chestnut trees to help them cope with the Asian fungus that decimated them in the twentieth century. Why not continuously manage all of the Earth's ecosystems to ensure their health and productivity in the long-term? Why should we not hijack the Earth's geochemical cycles, "weather" rocks artificially for carbon capture, cloud seeding to adjust the Earth's radiation budget and rainfall, etc, for our own benefit? Then, once eventually a problem emerges which the complex system cannot deal with, life on Earth complexes like a bizarre house of cards to a degree at least on the level of the end of the Proterozoic.
I'm not a crazy cartoon social Darwinist either. I want there to be a sense of love, cameraderie, volksgemeinschaft (hah!) as much as anyone and obviously the value of a human being cannot be reduced to their genetic material (although it is a larger determining factor than most would admit, simply due to its consequences). The only reason this stuff is necessary is because it's unavoidable.
But isn't it avoidable? But why do we even need this when we have vaccines? I'm sure you've been asking, you're not wrong to ask. Just because we didn't cook our food in the past, should we force ourselves to eat rotting raw meat until we reevolve iron stomachs? My answer would be no, but yes for vaccines, because the days of mass vaccination campaigns and modern medicine are numbered. Modern society's days are (fortunately!) numbered. The ability of human beings to make fire from wood, dry grass, dried dung, dried seaweed, peat, charchoal, some surviving brown coals or any number of other things in the future is not an issue.
The fruits of the industrial revolution are predicated on having fossil fuels. Not even taking into account dysgenic fertility trends which should reduce the number of per capita innovators able to deal with new incoming problems as world population growth levels off from the demographic transition, the energy return on energy invested of popular subsidised renewable energy sources is pathetic compared to fossil fuels. Nuclear power plants are sophisticated, take many rare elements to create and take longer to decommission than to build, also trying to nuclearise the entire world's energy generation would require building so many at this point that it's impossible (this is all acknowledging that it's been demonstrated we could maybe use polymers to filter uranium from seawater to make yellowcake). Hydroelectricity is heavily dependent on geography but will probably be post-industrialised humanity's primary source of electricity after all this is said and done, except it won't ever really be able to be at the level of what we enjoy today. The problem of hydrogen for any fuel or metallurgy (most comes from burning natural gas), energy for the Habers-Bosch process that produces much of the world's fertiliser (remember we're basically pulling N2 out of the air to make NH3), the problem of how little lithium is in currently estimated reserves, the fact that lower-grade reserves of anything are more resource-intensive and less economical to extract stuff from. The developed world is already borrowing way more than it can ever hope to repay to artificially prop up the standard of living of its people, does it seriously believe it can spend and subsidise its way out of a physical, energy-based crisis? Looking at Sri Lanka now, what hope does the third world have? Complex systems don't just decrease in complexity when fuel is taken from the fire, they starve. This civilisation will starve and die. This is a very brief and special period in human history which is now already beginning to come to an end before our eyes. The future will not be, cannot be, sterile. It will not have mass access to life-saving medicine that protects people from disease. These things will be relegated to small electrified outposts of the elite and a productive class whose occupations involve machinery. The majority of people, as in history, will exist on the land as peasants, toiling to produce precious calories, and this will likely remain the case until humanity goes extinct.
Surely there is 1. a healthy, actually positively healthy, level of disease/parasite load to have and 2. the % of offspring who don't survive at this level are unfortunately too genetically unhealthy to survive in the long term anyway, so nothing can really be done to help them but delay the foregone conclusion. What is it? How should parents behave regarding their children and sickness?
And should we be oddly glad when our children get head lice?
