Given the topic of this post, suggested by Santiago Verón, I’ve created yet another inadvertent series, so far including Breath of life and But so what. It’s all about that point I made at the start of the blog – that what it feels like to do it isn’t what it is.
This time, it’s warmth, which to be entirely physically accurate, means a discontinuous gradient of heat. The higher side of that discontinuity is “warmer” and the lower, “colder.” In a more boring landscape, there isn’t any sharp discontinuity, and so you really wouldn’t get perceived distinctions of that kind, but in our landscape, or more generally, biosphere, there are all kinds of media through which heat moves, with different densities and conductivities and stuff. Hence, “warmer” and “cooler” are all over the place.
So let’s take that to body temperature, and recognize something that contradicts the casual statements in many biology books: that all living things generate heat. Metabolic action in cells is a heat-producing event, period. In the majority of living creatures, the rate at which this occurs is low enough that the heat in question disperses out of the creature’s body effectively instantaneously. Hence most of the time their body temperature is the same as the location they’re in. This creates the illusion that they are “cold,” because, true, if heat from some new external source comes along, it diffuses in until it’s equilibrated.
The common casual taxonomy of warm-blooded vs. cold blooded is terribly flawed in a lot of ways. I explained one already: a typical living thing is plenty hot, internally, if it’s in a hot place; its blood does not “run cold” in an intrinsic sense. Another problem is using “blood” at all, in that what’s usually meant (a closed circulatory system) is only one of all sorts of ways to deal with internal body fluid. Historically, the whole distinction was socked into a vertebrate-centric view, such that no one called plants, for example, “cold-blooded” although they qualified in full.
All right, let’s get to the real terms. What I’ve been talking about so far, which gram for gram is pretty much every living thing aside from a few outliers, is ectothermy – metabolic heat is passively and invisibly shed, and if more heat comes around, it diffuses in. This contrasts nicely with endothermy: when the creature jacks up its metabolic activity far past the workings of its cells, such that heat cannot be lost as easily and thus builds up in the body. You are warm because the super-produced heat from your cells is backed up at your outer surfaces.
Geeky stuff: this is why increasing metabolism with body size follows an exponential curve instead of a straight line, ’cause the lower your surface-to-volume ratio, the slower the heat leaves. Also, why the dedicated endothermic critters have a higher-placed curve than the dedicated ectotherms, but otherwise it’s the same curve (see the lead graph).
Let’s bring in another variable, in fact, variability in and of itself: how constant is body temperature? Simplistically, one simply ties poikilothermy (variable temperature) to ectothermy, vs. homeothermy (constant temperature) tied to endothermy. It seems to make sense … except that living things refuse to cooperate. Obviously, an ectothermic creature who lives in a constant-temperature environment is ipso facto homeothermic; equally obviously, an endothermic creature who “jacks up” at varying rates and times, or at different rates per body part, is poikilothermic. When you say that, however, physiologists will start screwing up their faces and standing with one foot on the other, because that idealizing of mammals’ and birds’ “high, constant body temperature” vs. nonmammals’ “cold, varying body temperature” is very strong. People just want mammals and birds to be better regulators, that’s all, and they’ll start prattling about so-called “real” homeothermy and similar. There’s even a bogus term heterothermy to try to account for all those inconvenient creatures who dare to generate excess heat without being a bird or mammal, or doing it in the bird/mammal way.
So who does what, again? Well, the overwhelming biomass of living things is straightforwardly ectothermic and (given mostly varying environments) poikilothermic. A few animals leaven that with varying forms of endothermy , and of living animals, two types – mammals and birds – run so hot all the time that they maintain very high, constant temperatures. Let’s explode a myth or two.
- Endothermic homeotherms live very close to fatal levels of internal body temperature, specifically regarding brain tissue. They are all incredibly vulnerable to environmental heat, and their mechanisms to remove it are themselves grossly energy-costly.
- Most endothermic homeotherms are vulnerable to hypothermia well above freezing temperatures. The very mechanisms which keep you regulated within a pretty narrow, hot range go all kerflooey just a few degrees colder, and you drop dead even though the cold itself is not damaging your tissues.
- In areas with very cold, freezing winters, the ectotherms survive nicely, dropping their metabolic rate with the temperature and thus needing little or no food; for them, there is no such thing as hypothermia as long as they don’t actually freeze solid. In those same areas, the endothermic homeotherms die off in droves every winter.
- I should specify here that hibernation for the one type is very, very different from hibernation for the other.
- There is nothing “efficient” about endothermic homeothermy. You need insane amounts of food and insane amounts of water, and most of it is pissed away merely in producing heat. These populations are way more subject to size booms and crashes, with the associated risk of dying out in an area, because the resource variables are far more limiting than for ectotherms.
It’s that old vertebrate myth again: that a few heroic “active” types chinned themselves into “world dominance” because they weren’t sluggish, cold, stupid, and confused. As part of scrubbing away that myth, it’s perfectly understandable, to get excited about those big extinct guys called – wait, fair warning: when you say “the dinosaurs” as the general term, then somewhere, a paleontologist breaks into uncontrollable sobs. I’ll have to talk about the right terminology and the fun of how hot their various bodies were in some later post.
Whew! All that to set up the context for thinking about how heat has come to be equated with emotions among humans. I probably don’t have to elaborated, as the verbiage is baked in so thoroughly that the list would be epic. I really wonder how that plays out in non-European languages, though.
And then, that’s also tied into the notion of blood, verbally – a hot-blooded murder vs. a cold-blooded murder, a hot-blooded affair, and so on and on. Blood as living, the temperature status of the blood as the “feeling” of the life …
It even gets turned into an ethnic tag for humans, with the notion that “hotter” humans feel emotions more strongly and are more impulsive, when “hotter” seems to refer to the body heat but is specifically tagged toward the local environment. As if by living in a hotter place, you are personally necessarily hotter, and thus your emotions more intense and unregulated … although that’s taking it too literally, as such verbiage invariably ties it to an intrinsic feature of the person’s psychology, no matter where he or she happens to be standing. (Like all well-established racism, it’s ignored when necessary, so one must speak of, for example, Irish pugilism or even subhuman savagery without reference to the Mediterranean heat.)
To glance back toward the broader biology for a bit, you also find the stereotype that an ectothermic creature is necessarily less emotional in some way – whether mellower, duller, (conversely) more calculating, or more contemplative.
Now check this out: Bodily maps of emotions, which is pretty neat imagery material.
But let’s not misread it or be misled by perfervid headlines. It’s not actually a bodily map of emotions at all, but maps of blood temperatures by rather small fractions of degrees. It means that (presuming the subjects’ descriptions of their emotional states are trustworthy, statistically) blood is brought or not brought to various specific places under different emotional regimes. Considering blood is even more watery than your other tissues, it won’t surprise you that it’s a primary transporter of heat, considering, again, small but non-trivial differences. Therefore the images and the data as a whole set are absolutely valid in terms of varying circulation during emotional states, but the heat itself is not the emotion or “where the emotion is.”
[Addendum: Worse even than I thought! They didn’t even measure temperature; along with verbally stating their presumptive mood, the subjects also stated where they felt temperatures to be hot or cool. So there’s no non-socially-mediated data here at all.]
I’ll finish with a a difficult philosophical topic. I hammered in a phrase at the start, about how it feels isn’t actually the thing. Yet … how does that relate to emotions? Especially when you scrub away the romance and consider them to be physiological actions? Or to statements made as sincere commitments?
It’s easy to discount the phrase “just my opinion” even when the statement being made is rock-solid based on what the person has done in the past and is likely to do in the future. It’s almost impossible to discount the phrase “it’s my lived experience” even when the statement being made is quite dubious in terms of what actually happened or will happen. A moment’s thought shows that the precise phrase used is simply not the point at all.
When it comes to breathing, oxygen, blood, and heat, yes, I hope that these posts have shown that we mistake how it feels, specifically, proprioception, vestibular orientation, and interoception, for the biochemistry or other physiology that plays a causal role. But the same principle can be applied to what we think and feel. That is some murky territory to be striding about in. Let’s work with it more, in posts to come.