While I think there are very serious concerns that advancing technologies, and AI in particular, raise (such as lack of control over these systems with could be a tremendous threat, reduction of agency, and the potential for extreme concentration of power), if we can keep these technologies well under control and pointed at the betterment of humanity (a big if) I don’t think they have to destroy meaning. Here’s why:

While some people do derive a lot of their sense of self-worth from their work (such as myself), and such people could be especially hard hit if they are replaced by technology, there are, thankfully, many things that humans intrinsically value, and therefore, lots of potential sources of meaning. By seeking and then (at least to a reasonable degree) creating what we intrinsically value, we create meaning.

So let’s have a quick look at different human intrinsic values (i.e., things people value for their own sake, not as a means to an end) and how advancing technology, such as AI, may impact each of them:

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Spirituality and purity: there are no reasons I see that technology would have to interfere with spirituality, religion, or attempts to act purely. So these values could continue being a source of meaning.

Truth and learning: if anything, really effective technology can accelerate the search for truth and our ability to learn. At the same time, technology gone wrong could make the truth harder to discern (e.g., if technology facilitates misinformation outcompeting accurate information).

Achievement: this one could be hard hit by technology insofar as it’s related to doing things that eventually AI may do better than all of us. At the same time, humans find a lot of value in achievements regardless of non-human performance. For instance, people compete in sprints (even though cheetahs could easily outrun us) and find value in achievement in chess (despite AI being able to easily beat the best human). A lot of people also value personal achievement – merely doing the best you can, or improving to do better than your own previous results.

Freedom: while technology could impair freedom (e.g., if it concentrates power into the hands of certain actors, they might choose to limit freedom), there is also potential for technology to expand freedom a lot by allowing us to do many things that weren’t possible before, either because we didn’t know how to do them or because they were too costly before.

Pleasure, non-suffering, longevity: there is no fundamental tension between technology and these values, and technology may be able to improve these by reducing sources of suffering (such as disease), increasing lifespans, and making pleasure more easily accessible.

Happiness (as distinct from pleasure and non-suffering): This is a tricky one, because technology can cut both ways here. For instance, while it’s likely social media has increased some kinds of pleasure, it may well have reduced overall happiness for some people by making them more disconnected or impacting the way they see the world.

Caring, reputation, respect, loyalty, and virtue: these don’t have to be impacted by technology; we could continue valuing these in our relationships with others, even in a world where AI has replaced most work. The main threats I see here from technology are the ways that social media can cause people to spend less face-to-face time together, and the way that AI friends or “relationship” partners could take the place of human relationships.

Justice and fairness: this could go either way. Technology could concentrate power in a way that makes these worse or systematize bias. On the other hand, if the benefits of technology are distributed widely, they could create increased abundance. Technology also has the potential, if harnessed correctly, to reduce (currently commonplace) human bias.

Diversity: globalization tends to reduce diversity, and so technology could accelerate that trend. On the other hand, giving people more freedom through technology could end up increasing forms of diversity (such as how people choose to live their lives).

Protection: technology has the ability to make us safer, so while we may experience more protection (for ourselves and our loved ones), it also could mean that our own role of protecting others is reduced, which could reduce the meaning derived from providing protection. On the other hand, if technology is not developed thoughtfully, the world could feel increasingly chaotic and even become more unsafe, so protection could become even more important.

Nature: technology has a track record of destroying nature, so that trend may continue. However, it’s possible that with sufficiently advanced technology, that trend will go the opposite direction (e.g., cheap green energy makes it easier to protect nature). Technology often destroys nature either as a means to accelerate or as a side effect of acceleration, but sufficiently advanced technology may reduce that effect.

Beauty: technology has the possibility of increasing beauty in the world (making it easier to create and experience beauty), but also runs the risk of filling the world with generic slop.

Overall, while advancing technology may have a negative impact on some things that humans intrinsically value, as long as we don’t destroy the world with these technologies and avoid allowing extreme concentration of power from them, other intrinsic values may not be impacted or even be benefited by technology. As long as we can seek and (to a reasonable degree) create what we intrinsically value, there are sources of meaning available.

This piece was first written on November 16, 2025, and first appeared on my website on December 22, 2025.

Some people think that magic exists out there in the world.

Many others think that magic doesn’t exist at all.

I believe that a more accurate view than both is that magic “exists” but only in the specific way that “redness” exists.

Before I get into why I believe this, first let me explain what I mean by “magic.” I don’t mean magic as in Harry Potter or Lord of the Rings or even spells from Wiccan magic. I’m referring to situations where it’s common for us humans to perceive things as having properties that exist merely psychologically, but we view those properties as not merely psychological. For instance, we may think a property corresponds to something in the physical world when it doesn’t, or we may think that it has an existence that’s independent of psychology, which it isn’t. These “magical” properties that we perceive deeply change the way we interact with or relate to those things. I’ll give more examples later, but these “magical” experiences often arise for us humans in altered states, in nature, and in connection to death or sex.

Okay, so when I claim that this magic “exists” but only in the specific way that “redness” exists, what do I mean? Well:

Photons of red light are out in there in the world, but redness is not in the world – it exists only in our experience of the world. In other words, redness is part of the simulation constructed by our brains that forms the content of our moment-to-moment awareness. When photons of certain frequencies hit our eyes, specific signals are sent to our brains, which we then experience as seeing something red (unless we’re blind or color blind). The concept of “real” is ambiguous. Our experience of redness is “real” but it’s not real in the same sense that photons of light are “real.”

Similarly, magic is not out there in the world, but it is part of the simulation constructed by our brains – unless we’re “magic blind,” as some of us are.

What are some examples of this “magic” that I’m talking about? Well, magic occurs when our brains assign deeply important seeming non-physical aspects to things that go well beyond their physical properties.

To give some examples, most people experience magic as existing in:

1) The dead bodies of those we care about. To us, bodies are not just inanimate meat; they represent the person or animal who died – hence why desecrating a body or having s*x with a body seems immoral in a way that desecrating a rock would not. We treat dead bodies as though they are still the living person in a way that they aren’t anymore. They have important psychological properties, but it’s very easy for us to think and act as though these properties are not merely psychological.

2) Sex. To most of us, sexual activity is not like other physical actions (such as a handshake or even a vaginal or rectal exam from a doctor); we treat it as though it transforms people. This helps explain why some people would rather be severely physically assaulted than painlessly r*ped. It helps explain why people seem to view losing their virginity as being something of great importance that permanently changes you, even though usually there is nothing permanently physically different afterward. Sex has important properties psychologically, but we sometimes act as though it’s transformational in a way that is beyond psychology, even when it’s not.

3) Unlikely coincidences: to many people, they mean more than just the chance co-occurrence of those events. Many people see coincidences as saying something about the world that (I believe, at least) they don’t actually say. Yes, coincidences can have meaningful psychological effects – but it’s easy for us humans to view them as though they have prophetic or symbolic properties related to the world itself.

4) Certain human interactions: it’s not so uncommon for a person to work with a reiki energy healer (who either doesn’t touch the recipient or only puts hands on them lightly) and be convinced that a profound healing has occurred. In my opinion, such cases do not involve any physical healing, but they do produce an intense psychological experience for some people (especially people who come in already deeply believing in the practice). Not so dissimilarly, sometimes when encountering spiritual gurus people report having an intense psychological experience, even though the guru may have only said a few words to them (especially if they have pre-existing beliefs about the holiness of this guru). People have intense magical (psychological) experiences in these sorts of human interactions that (in my view) they sometimes misinterpret as involving physical changes or changes that are not merely psychological (such as healing of disease).

5) Nature: many people feel a deep connection to nature and that nature has more to it than animals, plants, water, and rocks – that it has some fundamental essence that is, itself, alive. They think some intelligence or consciousness is lurking in nature itself that (I think, at least) is not there.

6) Especially vivid dreams and psychedelic drug experiences: while most people acknowledge that many dream and psychedelic experiences are random or lack fundamental meaning, they are often interpreted as being real – for instance, as corresponding to an event that transpired, or that the being they witnessed during the experience is a real independent entity.

How can one understand what this “magic” is that I’m referring to? I think an analogy helps:

Suppose that there is a fantasy-themed augmented reality game that you play using AR goggles (i.e., Google Glass-style goggles through which you see reality, but the goggles layer game elements on top of reality for you to see and interact with). And suppose that in this AR game, magic is real – it’s simply one of the fantasy elements of the game. So when you’re playing that game, you REALLY DO experience magic (overlayed by the goggles onto physical reality).

Well, magic in real life is much like that, except the “AR goggles” are instead the simulation our brains make for us, which forms our experience of reality. This simulation is formed from all of our experiences of colors, sounds, smells, feelings, and so on that constitute our representation of the physical world. But, like AR glasses, they can have elements that don’t correspond to anything that’s physically there or that add additional features to things that are physically there. For instance, we know that some small percent of humans experience visual hallucinations that they perceive as being part of the world, but that are just part of the simulations made by their brains. This is a striking example, but none of us perceive reality directly; we only perceive the simulation our brains create, and none of our simulations match reality exactly as it is.

So magic, I claim, exists in our simulations of reality but not out there in reality itself.

Some people experience magic a lot less than others (I tend to be low on this scale, but I have close friends who are high on it). For those that are higher on the scale, magic is as real as redness – it just isn’t part of the external world – it’s a feature of our internal simulations that they experience deeply on a daily basis. It also isn’t merely a case of people being “imaginative” – we’re talking here about extremely common human experiences shared across most (and perhaps all) cultures.

Or, to summarize, magic exists – but it exists in “Experience Space” (the realm of what conscious beings experience), not in “Matter Space” (the realm of the physical, such as atoms and wave functions). In my opinion, a great many people who are high in the perception of magic make the serious epistemic mistake of believing magic exists in Matter Space. And those skeptical of magic sometimes make the mistake of dismissing it in a way that doesn’t properly acknowledge that others are having genuine, profound feelings *experiences* of magic – which can make magic believers feel gaslit. They are having those experiences, and those experiences are deeply meaningful to them – even if they are misinterpreting the nature of those experiences (e.g., incorrectly assuming they are real the way photons are real rather than real the way redness is real).

Or, as Duncan Sabien concisely summarized it in a comment on this essay: “Magic is in the map, not in the territory. But like. It really actually IS in the map! It isn’t not-there.”

This piece was first written on December 13, 2024, and first appeared on my website on February 12, 2025.

Below is my list of what I see as the deepest mysteries. 

What would you add to the list?

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LIST OF DEEP MYSTERIES ABOUT THE NATURE OF REALITY

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1. THE UNIVERSE

1.1 Eternity – Will our universe last forever? If it won’t, what will the end of the universe be like (e.g., a new big bang, a big crunch, time simply ending, something else)?

1.2 Genesis – Did our universe have a “starting point” (in a pre-existing expanse of time) or has it existed forever, or did time begin when the universe began?

1.3 Geometry – Does the universe extend infinitely in all directions, or is it finite? (To get a feel for how it might be finite without requiring a boundary, consider that the universe could be like the game Pac-Man, topologically – in the sense that, traveling long enough in any direction, you eventually get back to where you started). Is empty space perfectly flat (e.g., like an infinite plane but in multiple dimensions), or does the universe have implicit curvature (e.g., like the surface of a universe-sized orange)?

1.4 Constraints – Could the laws of physics be any different than they are, or is there some reason they have to be this way? Why are there the particular elementary particle types that we find (e.g. electrons, quarks, neutrinos, etc.) with the particular properties they have? Why are there the particular forces we find (e.g. electromagnetism, gravity, the strong nuclear force, etc.) with the particular properties they have?

1.5 Entropy – Why was our universe in a low entropy state in the distant past (with the matter fairly uniformly spread out, rather than, for example, all condensed into black holes)?

1.6 Reason – What’s the right explanation for WHY our universe came to exist? If it was not created by any form of intelligence, is the question even coherent to ask? If it was created by some form of intelligence, was it God, or some other form of intelligent beings (e.g. aliens creating a universe simulation in some vast computer)? If there was an intelligent creator, what is the nature of that creator (e.g. what is that creator like, what does that creator care about, etc.)?

1.7 Uniqueness – Are there other universes besides our own?

1.8 Travel – Are wormholes (connecting different parts of spacetime) actually possible? Is time travel forbidden by the laws of physics? Is instant teleportation impossible?

1.9 Dimensionality – How many dimensions of spacetime are there? (e.g., the standard view is four dimensions, which come from three spatial dimensions and a single time dimension, whereas ‘string theory’ suggests more, though most of those extra dimensions are believed to be really tiny/compact)

1.10 Computability – Can the universe be simulated to arbitrary accuracy on a normal computer (given sufficiently large amounts of memory and time), or is there something “incomputable” about the universe?

1.11 Expansion – Why does the universe seem to be expanding at an accelerating rate? If dark energy exists (the hypothesized element that is believed to make up most of the energy of the universe, not to be confused with dark matter), then what is it and why is it there?

1.12 Dark Matter – Does dark matter actually exist (i.e., the hard to detect element that appears to make up most of the mass in the universe)? If so, what is it made of?

1.13 Unification – How can general relativity and quantum mechanics be combined into a consistent theory that generalizes both (e.g., to model what happens when extremely tiny things are in strong gravitational fields)? Is ‘string theory’ the right path towards unifying general relativity and quantum mechanics (as many physicists believe), or is it a misguided approach (as a few physicists argue)?

1.14 Energy – Is there a positive, zero, or negative total amount of energy in the universe?

1.15 Divisibility – Are space and time infinitely divisible, or are there truly minimum lengths and durations?

1.16 Aliens – Does intelligent life (or even non-intelligent life) exist elsewhere in the universe? If intelligent life does exist elsewhere in the universe, why does it appear not to have reached us yet? Will we ever encounter life that has non-earth origins?

1.17 Life – Why does our universe have a set of physical laws and physical constants that allow for life (and consciousness) to exist at all? Some people argue that if the strengths of the basic forces of physics (like gravity) had been more than a certain increment stronger, or more than a certain increment weaker, life could not have formed in our universe.

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2. HUMANITY

2.1 Origin – What were the first “replicating entities” that all the humans today eventually developed from? Many religions say that God placed the first humans here, who eventually gave birth to all the others. But as for non-religious (evolutionary) explanations, there are various theories about what these replicating entities might have been (e.g., crystals, or special molecules that can make other molecules they bump into look like themselves)

2.2 Extinction – When will humanity go extinct? And what will cause humanity’s extinction?

2.3 Governance – Given the flaws and limitations of our species, and our current state of technology, what systems of governance, laws, and institutions would maximize human flourishing?

2.4 Happiness – Given the current state of the world, and the nature of and resources of one particular person, if that person wants to maximize their happiness, what should they do? What would a supremely intelligent being tell a human about how to become happier?

2.5 Qualia – Do humans have different internal experiences in cases where we typically assume them to have the same experience? For example, do there exist non-visually impaired people whose internal experiences of red (e.g., when looking at a red apple) are totally different than each other? For instance, could it be that one person’s experience of red is what another person experiences as blue? Or even that one person experiences reds as being somewhat more like what someone else experiences for blue things?

2.6 Humor – Why do humans have humor? There are many theories (e.g., “benign violation theory” and “superiority theory”) but none of them seem complete/comprehensive.

2.7 Music – Why do humans love music so much? It’s hard to understand this from an evolutionary perspective.

2.8 Yawning – Why do we yawn? And why are yawns contagious (i.e., seeing someone yawning tends to make others yawn)? There are various theories (e.g., to cool down the brain, or to get more oxygen). My preferred highly speculative explanation is that it’s a mechanism for groups to sync their sleeping, but it’s really hard to know if that’s right.

2.9 Nutrition – What should we do to not merely stave off malnutrition, but to thrive and be as healthy as possible? There seems to be a disturbing lack of consensus on this question (and it may turn out to depend a lot on individual people’s genetic and behavioral differences).

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3. KNOWLEDGE

3.1 Induction – is there a sound argument in favor of using induction that is non-circular (i.e., that doesn’t implicitly rely on using induction to make the argument)?

3.2 Occam’s Razor – Is there a sound justification for Occam’s razor (by which I mean the claim that “simpler” explanations are more likely to be true). If so, what’s the right notion of simpleness for a hypothesis that doesn’t require making arbitrary choices (e.g., avoiding the issue Kolmogorov complexity has where it introduces an arbitrary choice of representation language)?

3.3 Cognition – What algorithms are human brains running that allow humans to learn, remember, model the future, model other minds, reason, plan, theorize, and make inferences? Is it possible to build something broadly as smart as (or much smarter than) a human using just incremental improvements on top of today’s deep learning algorithms (combined with larger data sets and faster computation)?

3.4 Infinities – How should we think about maximizing the expected value of an action in contexts where we can’t assign strictly zero probability to outcomes of infinite value? The mere possibility (i.e. non-zero probability) of an infinite value seems to mess up the calculations completely. If we’re trying to maximize expected value, how do we resolve “pascal’s wager” and “pascal’s mugging” type situations?

3.5 Priors – How can we assign prior probabilities to hypotheses in a principled, computable way (that is, how do we decide what probabilities to assign to hypotheses BEFORE we are given evidence to use to update those prior probabilities)?

3.6 Anthropics – How do we perform reasoning and probabilistic estimation in “anthropic” scenarios where we are forced to consider the probability of even being the sort of mind that could end up in that scenario? What’s the right way to think about questions like “what’s the probability that I would end up being me rather than someone else?” or “what’s the probability that I would end up being a human rather than another species?” or “what’s the probability that I would end up being one of the last 1 billion people to be born before humanity goes extinct?”

3.7 Reference Classes – If we have multiple categories something falls into (each implying that we make different predictions about that things), how do we combine this information into a final prediction? For instance, if ALL we know is that X is a flying car, and flying machines rarely have property Y, yet cars usually have property Y, how do we make a principled “best” estimate of the chance that X has property Y? In other words, what’s the right way to think about combining the information Prob( Y, given A ) with Prob( Y, given B ) when what we really need to know is Prob ( Y, given A and B )?

3.8 Black swans – How do we probabilistically model situations (or do expected value calculations) when we know that “black swan” events (that are unlike any we have seen in the past) are possible, even though we don’t (by definition) know what these events will actually be like and how likely they are to occur?

3.9 Consciousness – Can we be 100% certain that some form of consciousness exists (because we have direct perception of conscious experiences), or should we be less than totally certain even about this?

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4. EXISTENCE

4.1 Many Worlds – Are the “many worlds” of quantum mechanics actually all literally existing (i.e., are they as real as what we all are experiencing right now)? Or does the mathematics just make it seem that way? If they are not really there, what’s the resolution to the “measurement problem” in quantum mechanics (e.g., how do we define what a measurement is and is not such that we have a complete description of when quantum wave functions collapse)?

4.2 Anything – Why does “something” exist, rather than there being nothing at all? Or does this question not even make sense to ask?

4.3 Time – Is there a meaningful sense in which all times that have and will happen exist at once, or do some times only come into existence (as time passes)? Note that the theory of relativity seems to undermine the possibility of a single-speed of time that is the same for all observers.

4.4 Morality – Is there any form of morality that is “objectively” correct? For instance, can moral statements like “murder is always wrong” be true or false in the way that “I once purchased a fedora” is either true or false? If any sort of objective moral truth is possible, what then is objectively true about morality (e.g., utilitarianism, the categorical imperative, virtue ethics, theological ethics, etc.)?

4.5 Non-physical – does anything exist that is not merely made of atoms / not bound by our laws of physics, that can directly cause changes in our world (e.g. souls, ghosts, gods, spirits, the devil, etc.)?

4.6 Time travel – is time travel prevented by the laws of the universe? If it is not prevented by the laws of the universe, has it or will it ever happen? Potentially related: is it possible to exceed the speed of light, or is that literally impossible (as our current theories seem to tell us)?

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5. CONSCIOUSNESS

[Note that, by “consciousness,” I mean the state of having “internal experiences.” A being has consciousness if there is “something that it’s like” to be that being. For instance, there is something that it’s like to be you, but not something that it’s like to be a chair. You have internal experiences, like experiencing the taste of a pineapple or the color of a red apple, but a chair has no experiences. You have consciousness, in the way I’m using the term, but a chair (almost certainly) doesn’t.]

5.1 Justification – Why is there consciousness at all? Couldn’t the universe be just the same as it is now except without any internal experiences at all (i.e., with no consciousness)?

5.2 Requirements – What sort of configurations of matter are necessary to give rise to consciousness? Would it be possible to build a physical device to measure consciousness? If so, what would such a device need to be like?

5.3 Physics – How do we unify the existence of consciousness with the currently known laws of physics (since examining our known laws of physics would not allow you to infer that consciousness experiences even occur)?

5.4 Quantum – Does the human brain exploit quantum physics in a meaningful way, such that it is hard to understand what the brain is doing without using a quantum mechanical explanation?

5.5 Free Will – Why do we have the persistent sense of having free will, even though (given our current understanding of physics) our actions are fully and completely determined by whatever happened a moment before (plus quantum uncertainty)?

5.6 Minimal – Which beings have consciousness? Do atoms? Viruses? Bacteria? Blood cells? Lice? Ladybugs? Spiders? Snails? Frogs? Mice? Beavers? Toucans? What’s the “simplest” possible brain or system or algorithm that can experience consciousness?

5.7 Evolution – Did consciousness come about as a result of evolution (i.e., was it created by selection pressures), and if so, what is its survival function exactly?

5.8 Algorithmic – Is it possible for an algorithm run on a digital computer to experience consciousness?

5.9 Intelligence – Can something be much more intelligent than human beings (broadly speaking) and not have consciousness? Can something behave just like a human in all ways relevant to intelligence and yet not experience consciousness (i.e., can “philosophical zombies” exist?)

5.10 Teleportation – If a teleportation device existed that could make an essentially perfectly accurate copy of you out of new atoms, with all your memories and personality intact, but it destroyed your original self just before assembling the new copy of you, would the copy be you, in the same sense that you one second from now is still you?

5.11 Macro – Is it possible (even if extraordinary difficult) for a large-scale, purely mechanical system to have consciousness, for instance, a massive machine made out of gears and pulleys? Could a very large number of people, if they were all carrying out coordinated movements that were designed to match the algorithmic information processing of a brain, temporarily create a large-scale consciousness?

5.12 Agent – What’s the right definition to use for a single “being” or “agent” that properly distinguishes it from all other beings, while still handling even weird thought experiments. (For instance, where a person’s brain is split into two but continues to operate, or where a brain is slowly replaced with pieces of another brain over a long period of time, without ever ceasing operation)?

5.13 Finality – Does all experience cease after death, as atheists typically believe and as spiritual and religious people typically deny?

Many causes of a population’s height distribution are not hereditary. For example, a population’s height is also determined by economic factors, like whether there was malnourishment among children or pregnant mothers. Cultural causes may also be at play, such as the extent to which height was valued in mate selection or whether the population has a gender imbalance. Even smaller cultural elements, like whether it is common for children to be enrolled in grueling, height halting athletics, whether height altering surgery is used to satisfy aesthetic preferences, and whether growth hormone is administered to children, can have an effect. Height is also influenced by long term trends, such as the percentage of people in each age group.

So, to what extent is height genetic? There is no single answer to that question. It depends on what you mean, and it may be that none of the answers satisfy what you think you mean by the question.

You could ask the extent to which one individual person’s height (as measured at one particular point in time) was “caused” by genetics. Genetics did cause their height, in the sense that, if you swapped some of their genes, they would have had a different height. Their height was effected by their nutrition as an infant (e.g., protein, vitamin A, vitamin D, and calcium). If they had better or worse nutrition, their height could have been different. Their height was also caused by their age since if you’d measured their height when they were one year old, they would have been a lot shorter.

Suppose you have an apple tree that has seven apples. What caused it to have seven apples as opposed to fewer or more? Was it the amount of sunlight it got? The amount of water? The average temperature? The soil it was planted in? This question doesn’t make sense to ask. The number of apples that this tree has is a complex function of all of these variables (plus many more), and even if we knew this complex function, at best all we could say (by taking derivatives with respect to one variable at a time) is how the number of apples would have changed with a small change in one of the inputs (holding the others constant), but even that isn’t the question we are attempting to ask.

Okay, perhaps it is more meaningful to talk about groups rather than individuals. We can ask, within a particular group, the extent that height is genetically determined.

The first problem we encounter is that the answer may depend a lot on the group we pick. If we are talking about a group of males and females who are all the same age and who all received the same nutrition when young, then we’ll find that a larger percentage of the variation in height is explainable from genetics than if we’re talking about a group of males of varying ages and varying early nutrition. The more variation that happens to have been caused by non-genetic factors like nutrition, the less heritable we’ll find the trait to be.

For instance, according to Scientific American [1], a study of Finnish twins found the heritability of height to be 78% for men and 75% for women. Another study found the heritability of height in China to be 65%. Hence, it technically makes no sense to say, “How much of height is determined by genetics? (full stop)” We have to pick a group G and then ask, “How much of height for group G is determined by genetics?” We’ll get a different answer for Finland than we will for China, and we’ll get a different answer for Finland in 2017 than we will for Finland in 1990. The distribution of genes changes over time in a population, as do the strength of environmental impacts, which, of course, also change the extent to which traits seem to be caused by genetics.

Okay, so suppose we’ve picked a group G. How then would we calculate how heritable height is within that group G? Well, ideally, we’d look at identical twins within G that were separated at birth and raised by different families. Because the age of these twins is identical and the genetic factors are close to identical (save for chance mutations and differeing gene expression), if the environmental factors are selected purely at random (with likelihood representative of how those factors affect members of G), we can assume that differences in the height of identical twins are mostly caused by non-genetic factors. Hence, we can look at the ratio of the amount height varies among twins raised in different families (the environmental component) to the amount that height varies among unrelated people raised in different families (which includes both genetic and environmental components). A similar sort of analysis can be done by comparing identical twins to fraternal twins.

Unfortunately, even these sorts of analyses make a variety of assumptions. They assume that the hormonal environment of the womb (which is shared by identical twins but which may not be mainly genetic) has no effect on height. They assume that the families that give birth to identical twins and the families that adopt them are representative of the broader population (e.g., if twins are adopted only by families that can provide for their children proper amounts of nutrition whereas many other families don’t, then the calculations will be skewed). And they assume that there are no hidden non-linear interactions between genetics and environment (for instance, if some genes cause a person’s height to be more sensitive to early nutrition, we may falsely chalk up any such height differences purely to nutrition differences when genetics are partly responsible). There is also, of course, sampling error. A large number of twins is hard to come by, and if we only manage to get 100 of them, the error in our heritability estimates could be +- 10% from just noise alone, not taking into account the other potential issues.

While the measurement of height is quite straightforward, for other variables of interest, we may find different heritability depending on the exact definition of the trait used. For instance, this remarkable chart [3] showing happiness heritability estimates that range from 18%-47% (mean=32%) for life satisfaction measures and 23%-59% (mean=36%) for wellbeing measures. The wide range of values occurs in part because of the variability in which measures of happiness were used [4], but also because of the different populations studied, different techniques used to make the estimates, and ordinary sampling error [5].

There are enough challenges with computing heritability that, at least occasionally, when the assumptions of the models are accidentally violated, the results of such analyses are hilariously non-sensical [2]: “‘Did you have your back rubbed’ came out to 92% [heritable] for males and 21% for females. Many of the resulting [narrow heritability estimates] exceed 100%. For example, the HRs of ‘Did you wear sunglasses after dark?’ Are 130% for males and 103% for females.”

What is perhaps most pernicious about calculations of heritability, though, is that people assume a high level of heritability implies a trait cannot be changed through environmental interventions, and more generally, people assume that the proportion that is heritable cannot be changed. You hear this, for instance, when people investigate the heritability of happiness and assume that the heritable portion is fixed, a predestined part of our fate that we societally have no control of.

The idea that the proportion attributed to genetics is unchangeable is false. For instance, you may have a group where CURRENTLY nearly all of the variation in height is determined by genetics, but height could still be dramatically changed via interventions such as better childhood nutrition or growth hormone. Heritability only tells us about the fraction of the CURRENT variation that seems to be due to environmental differences, not the fraction that COULD BE if we were to change the environment.

[1] https://www.scientificamerican.com/…/how-much-of-human…

[2] On Models and Muddles of Heritability https://link.springer.com/…/10.1023%2FA%3A1018358504373…

[3] https://www.ncbi.nlm.nih.gov/…/PMC4346667/figure/Fig2/

[4] https://www.ncbi.nlm.nih.gov/…/PMC4346667/table/Tab1/

[5] Genetics of Wellbeing and Its Components Satisfaction with Life, Happiness, and Quality of Life – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4346667/