#human physiology

The Sydney funnel-web spider is one of the most dangerous spiders in the world. Its fangs are 5 mm (0.2 in) long; they are hardened & downward-pointing & strong enough to penetrate our fingernails, skin & leather. Worse yet is the powerful venom it contains. If one should bite a child & they didn't receive prompt medical intervention with antivenom, the child would die within minutes. The antivenom is a lab-madeantibody treatment that binds to atracotoxins & neutralizes them. The venom contains atraxotoxins, a family of neurotoxic proteins that force nerve cells to fire uncontrollably, causing muscle spasms, breathing difficulty, sweating & drooling. The toxin can overload the heart & lungs, making it a struggle to breathe & leading to a dangerously fast heart rate, collapse & death. Males are more dangerous than females because their venom contains more potent atracotoxins. They wander more, increasing human encounters. Thankfully, modern medicine has eliminated fatalities since 1981.

But not so for the deadliest spider on Earth—the Brazilian wandering spider. It has multiple confirmed fatalities in South America, including Brazil, Colombia, Peru, Ecuador, & Venezuela, as well as parts of Central America. They hide in banana plants, forest floors, sheds & homes at night. It is highly aggressive, & its venom is a cocktail of neurotoxic peptides, toxins 1 through 6. Each number produces different symptoms & targets a specific part of the body; for example, Tx1 disrupts nerve firing & Tx2 causes pain, muscle dysfunction & priapism in males (a prolonged painful erection that lasts for 4 hours or more without sexual stimulation).

You might have guessed I'm talking about hot flashes or flushes if you prefer. Whatever, a woman in her mid-40s suddenly wakes up, overheated, sweating & wondering why it's so hot in the house. Until she sees the thermostat set for 70°F (22°C), Or maybe she's midway through a work presentation when heat suddenly rises from her chest to her face, & she wonders if everyone else in the room sees her blushing. Even if you're young now, if you're a woman, you will get them. The hot flash is a rite of passage for the majority of women in either perimenopause (the years leading to menopause) or the years beyond it. Menopause is officially diagnosed after 12 consecutive months without a period, but the hot flashes don't always get the memo. Most women experience a hot flash about 4 1/2 to 5 years after their last period.

Hot flashes & menopause are nothing new. In fact, women have experienced them for as long as Homo sapiens have existed. The purpose of menopause is to shift older women from making babies to helping their existing descendants survive, a strategy known as the "Grandmother Hypothesis." The cause of menopause is that the ovaries make less estrogen, and the brain's internal thermostat—the hypothalamus—becomes hypersensitive to even small shifts in temperature. The body "thinks" it's overheating, even when the actual temperature hasn't changed much. In response, their bodies try to cool them down. Blood vessels dilate, which is supposed to help dissipate some of that heat but then triggers a sweating reflex. There's a lot of variability in how women experience hot flashes—some describe very mild symptoms, others grapple with profuse sweating, some get them only in the day, & others experience night sweats. Night sweats often last longer than day sweats.

Menopause averages 7 years, but the short end is just 1-2 years, while the longer end is 10-11 years, the latter experienced by black women. Why? Studies show that their hypothalamus is more likely to misfire & keeps misfiring longer. It's like a smoke detector going off when you make toast—it becomes hypersensitive. They have sharper & more irregular estrogen drops. The hormone estrogen is the master regulator of the female reproductive system, so when estrogen levels fall just before menopause, the sudden absence of estrogen's calming, soothing, temperature-stabilizing influence causes the symptoms of menopause, including mood swings, vaginal dryness, & sleep problems as well as the hot flashes & sweats. Asian women report the fewest hot flashes. But new research points to other factors behind hot flashes. They are influenced by neurotransmitters in the hypothalamus called KNDy neurons (pronounced "candy") as well as kisspeptin, dynorphin & neurokinin B, which become overreactive & have more of an impact on how women regulate their internal temperature than even estrogen hormones.

It seems that pregnant women are counting on red cabbage for more than just a healthy meal. Red cabbage is having its moment on the internet. Once you boil down its leaves, the deep blue color left behind can be used as a pH indicator, which means it can detect if something is an acid or a base. Apparently, some women trust cabbage juice as much as they trust an ultrasound to determine the sex of their baby. If the solution is mixed with urine & turns red, a boy is on the way, but if it turns pink, the baby is a girl. The problem is that pregnancy changes the pH of a woman's urine in different ways, so there's no scientific basis to judge sex determination based on a pregnant mother's urine. Pregnant women often have more acidic morning urine. Afternoon urine is more dilute. pH swings from 4.5 to 8.0 & has no relation to fetal sex.

The first cue is our breath. No, garlic, or any other food for that matter, won't repel them. (That only works against vampires). How do I know that? Because I've never been bitten by a vampire, unless you count those monstrous little blood-sucking ones. Aside from drug commercials, I'm hard-pressed to think of anything more annoying than female mosquitoes. (Sorry, girls, it's just the females that bite.). That's just biology. Whether that has anything to do with the human "war of the sexes" is, of course, debatable. But the fact that my wife is feverishly looking for her cast-iron pan as I write this outdoors, though, is not up for debate. Mosquitoes have been around for at least 150 million years, long before T. Rex, Triceratops, or Velociraptors. We have fossils to prove it. Only female mosquitoes bite us because blood is baby food. They need the nutrients in the blood to make eggs.

Researchers used high-speed infrared cameras to track mosquito movement in 3 dimensions. They recorded 1,000s of flight paths & then applied some "math" to figure out what actually guides mosquitoes to their next meal. Math from the paper—WTF, I understood nothing from it except for "2" & nothing else. But the takeaway is that, perhaps unsurprisingly, mosquitoes do not rely on a single cue. The first is vision. Mosquitoes are strongly attracted to dark colors. This has been proven in controlled experiments. Dress a person half in black & half in white, & the mosquitoes don't hesitate—they go to the dark side. This isn't because mosquitoes have a refined sense of fashion or are into goth. It's just that dark objects stand out against lighter backgrounds, making them easier to detect. Dark colors absorb more solar radiation, heating up by 5-20°F (3-11°C). Mosquitoes detect this even in low light. They use motion & contrast to lock onto shapes from 15-30 ft (5-10 m) away.

Perhaps even more than this is CO₂. Humans exhale 2.3 lb (1 kg) of CO₂ per day, & mosquitoes detect a CO₂ plume from 30 to 50 ft (9 to 15 m) downwind. But this doesn't attract them to your skin—it tells them to start searching in this direction. Once detected, they switch into host-seeking mode, increasing flight speed & zigzag scanning. The 3rd cue is heat emanating from our skin. Once within 3-6 ft (1-2 m), mosquitoes switch to thermal imaging. They can detect temperature differences as small as 0.1-0.3°F (0.05-0.15°C). They follow the gradient towards the warmest, moistest surface. Ankles, wrists, necks & your face & head. It's a perfect mosquito magnet—dark features, a warm, moist surface & a steady stream of CO₂ from breathing. Combine all 3, & you're on the menu somewhere between the asparagus tips & the crème brûlée. There's still another attractant.

Our skin microbiome produces 100s of VOCs (volatile organic compounds) such as lactic acid, ammonia, butyric acid, acetone, isovaleric acid & the carboxylic acids (the "feet smell" molecules). This is the same reason mosquitoes are attracted to our feet as they are to smelly cheeses such as Limburger (the cheese used in the famous Ig Nobel mosquito study), Brie & raclette. Human feet & smelly cheese both contain short- and medium-chain carboxylic acids (isovaleric acid, butyric acid, propionic acid, acetic acid & sulfur compounds). They are both "fermentation projects" run by similar bacteria, the key microbe being Brevibacterium linens. These live between our toes & on the rinds of the smelly cheeses. They smell like feet, sweat, ripe cheese, smelly socks & tangy funk. The French poet Léon-Paul Fargue (1876-1947) called the cheeses (and our feet) 'les pieds de Dieu'—the feet of God.

First off, yes, the anus is an organ. It includes sphincter muscles, mucosal lining, nerves, blood vessels & connective tissue. It's not just a hole but a multi-tissue functional complex. 640 mya, for the first time ever, anuses are about to evolve & change the course of history & life on Earth forever. To fill in the gaping hole of knowledge of the anus, let's go back 3.7 million years, when life on Earth began with protocells, formed either in the intense heat of geothermal vents or arrived on Earth from an asteroid. These protocells eventually evolved into cyanobacteria, which began to transform radiation from the Sun into chemical energy. They extracted electrons from the hydrogen using the sun's energy & released oxygen into the atmosphere, known as "the great oxygenation." There was a great boom in life after that with mosses, ferns, plants & animals, following around 640 mya, beginning with the sea sponge. They were largely static, but they fell off in polyps that would then begin to move & traverse the sea bottom, where plenty of food & detritus littered the ocean's floor.

The theory goes that around 541 mya, when there was a great Cambrian explosion, it was likely due to the creation of animals now having a head & more importantly, an anus. We know they existed from fossils from that era. You cannot evolve a head that eats without also evolving a direction of travel. Once you have forward motion (a front end that encounters food first), you need a backend to expel waste behind you. It's all about movement, & the ability to move is all about getting food. This movement is related to our nervous systems & our brains in animals & of course, in humans. So, for us to gain a brain that could have consciousness, we first needed to get an anus. Without it, animals would have stayed tiny, simple & energetically limited. The anus enabled constant nutrient intake, longer digestive tracts, bigger bodies, more cell types & tissues & more active lifestyles. Energy is the currency of evolution; the anus massively increases the "budget." The anus forms first in the human embryo.

All chocolate begins with the cocoa or cacao bean, which is the seed of the Theobroma cacao tree, a tropical plant native to Central & South America. https://x.com/Anthon19_/status/2039733749684781280?s=20 Processing the bean gives you cocoa solids (the bitter part) & cocoa butter (the fat part). Sugar is added as well as an emulsifier called lecithin. Sometimes, vanilla flavoring is also added in the form of vanillin. Milk chocolate also contains milk powder or condensed milk. Dark chocolate contains a much higher proportion of cocoa solids, from 50-90%, whereas milk chocolate contains just 20-30% cocoa solids.

Dark chocolate has more protein, saturated fat, slightly more minerals & caffeine than milk chocolate. One row of dark Lindt chocolate (the kind I eat) has 16 mg of caffeine vs. the same amount of milk chocolate, but that is still far below a typical cup of coffee, which contains about 100 mg. Dark chocolate is also rich in plant compounds called polyphenols, about 5 times more than milk chocolate has. Such compounds are healthy & beneficial because they neutralize free radicals (bad actors that strip electrons from cells, damaging them). Polyphenols like flavonols increase nitric oxide, which relaxes blood vessels & causes vasodilation & improved blood flow within 1-2 hours of consumption. There is a slight reduction in systolic blood pressure (the higher reading) of about 2-5 mmHg. It may help improve mood by increasing serotonin levels. To get any benefit, though, you'd need to consume at least 4 squares of a standard 70-85% chocolate bar.

The first is to ditch HFCS for cane sugar. Cane sugar (sucrose) is a 50/50 split of glucose & fructose. HFCS makes up about 55% fructose & 45% glucose. It doesn't matter to your body which one you consume, as the body ultimately breaks them down into glucose & fructose, & meta-analyses & systematic reviews show no significant differences in effects on body weight, BMI, waist circumference, blood pressure, cholesterol, or triglycerides. The scientific consensus is that total added sugar is harmful (regardless of source), whether it came from cane sugar or HFCS. Verdict? Same game, different jersey.

A current talking point is that we should be eating "real food" & avoiding ultraprocessed foods (UPFs). But what does "real" food mean? It's logically absurd, after all; all food is "real," or it wouldn't be food. Marketing co-opted the term. But I do agree that we should cut back on UPFs and gravitate towards whole foods, minimally processed foods, and foods not engineered for hyper-palatability, which is especially true for UPFs. Sandwiches are an example. These can be made of only 1 or 2 ingredients, but if they're ultra-processed, meaning adding many layers on top, they can become more nutritious (depending on what you put inside them). The term "ultra-processed" must be taken into context.