Part of the sequence: Rationality and Philosophy

We have already examined one source of our intuitions: attribute substitution heuristics. Today we examine a second source of our intuitions: biological evolution.


Evolutionary psychology

Evolutionary psychology1 has been covered on Less Wrong many times before, but let's review anyway.

Lions walk on four legs and hunt for food. Skunks defend themselves with a spray. Spiders make webs. Each species is shaped by selection pressures, and is different from that of other species.

Certain evolved psychological mechanisms in humans are part of what makes us like each other and not like lions, skunks, and spiders.

These mechanisms evolved to solve specific adaptive problems. It is not an accident that people around the world prefer calorie-rich foods,2 that women around the world prefer men with resources,3 that men around the world prefer women with signs of fertility,4 or that most of us inherently fear snakes and spiders but not cars and electrical outlets.5

An an example of evolutionary psychology at work, consider the 'hunter-gatherer hypothesis' that men evolved psychological mechanisms to aid in hunting, while women evolved psychological mechanisms to aid in gathering.6 This hypothesis leads to a list of bold predictions. If the hypothesis is correct, then:

  1. Men in modern tribal societies should spend a lot of time hunting, and women more time gathering.
  2. Humans should show a greater tendency toward strong male coalitions than similar species in which males do not hunt much, because strong male coalitions are required to hunt big game.
  3. Because meat from most game comes in quantities larger than a single hunter can consume, and because hunting success is highly variable (one week may be a success, but perhaps not the next week), humans should exhibit food sharing and reciprocal altruism.
  4. We should expect to see a sexual division of labor, due to the different traits conducive for hunting vs. gathering.
  5. Men should exploit status gains to be had from 'showing off' large hunting successes.
  6. Men should have superior cognitive ability to navigate across large distances and perform 3D mental rotation tasks required for throwing spears and similar hunting acts. Women should have superior cognitive ability with spacial location memory and object arrays.

And as it turns out, all these predictions are correct.7 (And no, evolutionary psychologists do not only offer 'postdictions' or 'just so' stories. Besides, probability theory does not have separate categories for 'predictions' and 'postdictions'.)


Kin loyalty

Consider the intuition that we have more responsibility for the well-being of our close relatives than for the well-being of distant relatives or strangers. We would expect human evolution to produce exactly such an intuition given Hamilton's rule, which states that the reproductive cost to an agent is less than the genetic relatedness of the recipient to the agent multiplied by the additional reproductive benefit gained by the recipient of the altruistic act.

That's a mouthful, so instead let me illustrate the consequences of Hamilton's rule:

Imagine that you pass by a river and notice that some of your genetic relatives are drowning in a ferocious current. You could jump in the water to save them, but you would pay with your own life. According to Hamilton's rule, selection will favor decision rules that, on average, result in your jumping into the water to save three of your brothers, but not one. You would be predicted not to sacrifice your own life for just one brother, because that would violate Hamilton's rule. Using the logic of Hamilton's rule, evolved decision rules should lead you to sacrifice your own life for five nieces or nephews, but you would have to save nine first cousins before you would sacrifice your own life.8

Hamilton's rule has indeed been observed at work in a wide variety of contexts.9

My intuition that I am more responsible for the well-being of my brother than my cousin, and more responsible for the well-being of my cousin than a stranger, looks like a good candidate for an evolved intuition.



Uneducated people around the world believe that organisms come in discrete packets, and that each species has an 'essence' that produces its form and abilities. The intuitive appeal of this essentialism often trumps the explicitly learned gradualism of biological evolution. Even someone who has read Richard Dawkins argue against essentialism might find himself the very next day stuck in essentialist thinking. Why? Many researchers have suggested that an evolved, intuitive 'folk biology' is responsible.10

These essentialist intuitions emerge early in life across all cultures we have studied.11 For example, children may believe that

...if you remove the insides of a dog, it loses its 'essence' and is no longer really a dog anymore - it can't bark or bite. But if you remove its outsides or change its external appearance so that it doesn't look like a dog, children still believe that it has retained its essential 'dogness.'12

Many researchers think that essentialist intuitions evolved because it's useful for humans to respond to organisms in this way. With essentialist thinking, we can very quickly drop organisms into categories concerning what we can and can't eat, what we can capture, what might capture us, and so on.

Essentialism has had a long-lasting hold on the minds of many philosophers, and greatly influenced their conclusions even after Darwin.


Heuristics and biases

Human reasoning is subject to a long list of biases. Why did we evolve such faulty thinking processes? Aren't false beliefs bad for survival and reproduction?

Many researchers suggest that while humans are poor at formal logic and Bayesian inference, humans display a kind of 'ecological rationality'.13

Over evolutionary time, the human environment has had certain statistical regularities: Rain often followed thunder, violence sometimes followed angry shouts, sex sometimes followed prolonged eye contact, dangerous bites often followed getting too close to a snake, and so on. These statistical regularities are called ecological structure. Ecological rationality consists of evolved mechanisms containing design features that utilize ecological structure to facilitate adaptive problem solving.

The shape and form of cognitive mechanisms, in other words, coordinate with the recurring statistical regularities of the ancestral environments in which humans evolved. We fear snakes and not electrical outlets...

[Moreover], theories of formal logic that are content independent... are exceptionally poor at solving real adaptive problems. The world is full of logically arbitrary relationships: Dung happens to be potentially dangerous to humans, for example, but provides a hospitable home for dung flies. So applying formal logic cannot in principle solve the adaptive problem of avoiding dung. The only thing that can solve it is a content-specific mechanism, one that has been built over evolutionary time to capitalize on the recurring statistical regularities associated with dung as it interacted with our hominid ancestors.14



Our brains may have evolved intuition-generating mechanisms that worked for solving particular adaptive problems in the ancestral environment, but we may not have evolved psychological mechanisms that generate accurate intuitions useful for doing philosophy. For example, it seems unlikely that we evolved a mechanism that gives us reliable intuitions about the metaphysical possibility or impossibility of zombies.


Next post: Intuition and Unconscious Learning

Previous post: How You Make Judgments




1 Recent introductions to the field include: Buss (2011); Workman & Reader (2008); Gaulin & McBurney (2003). It is also worth mentioning one of the major problems with evolutionary psychology. Evolutionary psychologists tend to focus on subjects that are difficult to test because they are uniquely human but also universally human, which is bad for testability (see here and here). For other difficulties, see Problems in Evolutionary Psychology.

2 Birch (1999); Krebs (2009).

3 Buss et al. (1990); Buss & Schmitt (1993); Khallad (2005); Gottschall et al. (2003); Gottschall et al. (2004); Kenrick et al. (1990); Gustavsson & Johnsson (2008); Wiederman (1993); Badahdah & Tiemann (2005); Marlowe (2004); Fisman et al. (2006); Asendorpf et al. (2010); Bokek-Cohen et al. (2007); Pettay et al. (2007).

4 Signs of fertility that men prefer include youth (Buss 1989a; Kenrick & Keefe 1992; Kenrick et al. 1996), clear and smooth skin (Sugiyama 2005; Singh & Bronstad 1997; Fink & Neave 2005; Fink et al. 2008; Ford & Beach 1951; Symons 1995), facial femininity (Gangestad & Scheyd 2005; Schaefer et al. 2006; Rhodes 2006), long legs (Fielding et al. 2008; Sorokowski & Pawlowski 2008; Bertamini & Bennett 2009; Swami et al. 2006), and a low waist-to-hip ratio (Singh 1993, 2000; Singh & Young 1995; Jasienska et al. 2004; Singh & Randall 2007; Connolly et al 2000; Furnham et al 1997). Even men blind from birth prefer a low waist-to-hip ratio (Karremans et al. 2010). Note that standards for beautiful faces emerge before cultural can have much effect (Langlois et al. 1990) and that standards of beauty are relatively consistent across cultures (Cunningham et al. 1995; Cross & Cross 1971; Jackson 1992; Jones 1996; Thakerar & Iwawaki 1979).

5 Buss (2011), pp. 92-94.

6 Buss (2011), p. 85.

7 Evidence cited by prediction number. 1: Hewlett (1991); Lee (1979). 2: Tooby & DeVore (1987). 3: Trivers (1971). 4: Roskraft et al. (2004); Tooby & DeVore (1987). 5: Hawkes (1991); Wiessner (2002). 6: Silverman & Philips (1998); Silverman et al. (2000); Eals & Silverman (1994); Silverman et al. (2007); New et al. (2007); Silverman & Choi (2005); Lippa et al. (2010).

8 Buss (2011), p. 238-239.

9 Buss (2011) calls Hamilton's theory of inclusive fitness (expressed in Hamilton's rule) "the single most important theoretical revision of Darwin's theory of natural selection in the past century" (p. 239). For a review of some of the evidence that supports Hamilton's rule, see Buss (2011), chapter 8.

10 Atran (1998); Berlin (1992); Keil (1995); Medin & Atran (1999).

11 Sperber & Hirschfeld (2004).

12 Buss (2011), p. 73.

13 Tooby & Cosmides (1998). Haselton et al. (2009) say humans are 'adaptively biased,' while Kenrick et al. (2009) say we are 'adaptively rational.'

14 Buss (2011), pp. 396-397.



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Another problem with using a list of postdictions to support evolutionary psychology is that you have not shown that it cannot also predict the opposite - as it sometimes can if you choose to tell the story differently.

Premise: Men in tribal societies spend a lot of time hunting, and women more time gathering.

  1. Human males should show a greater tendency toward isolation than in similar species in which males do not hunt much, because hunting for small and medium-sized game is a solitary endeavor.
  2. All people should claim status from large successes, because of our background in tribal politics.
  3. Women should have superior cognitive ability to use and construct more pieces of rudimentary technology and perform 3D mental rotation tasks required for weaving baskets and similar acts. Men should have superior cognitive ability with spatial location memory and perception because of its use in hunting.
In response, I just want to repeat everything Eliezer said here and here, and point you to this article.
This is the most trenchant criticism in my opinion. I disagree with those who say that postdictions are worthless. But they've got to be honest postdictions. They have to be real probabilistic consequences of the logic of the theory.
Good. The reason is explained by Yudkowsky: and: Probability theory has no separate category for 'prediction' and 'postdiction'. But yes, you need to be making predictions and postdictions that actually follow from the math of your theory. Though, semitechnical theories can still build up a high enough score to beat out rival theories.

For those people who claim that evolutionary psychology isn't predictive:

These data show that children living with one genetic parent and one stepparent are roughly forty times more likely to be physically abused than children living with both parents.This greater risk rate occurs even when other factors such as poverty and socioeconomic status are controlled. Daly and Wilson concluded that "step-parenthood per se remains the single most powerful risk factor for child abuse that has yet been identified".... Some people, of course, might claim that such findings are "obvious" or that "anyone could have predicted them." Perhaps so. But the fact remains that hundreds of previous studies of child abuse failed to identify step-parents as a risk factor for child abuse until Daly and Wilson approached the problem with an evolutionary lens.

Buss (2008). Evolutionary Psychology: The New Science of Mind (3rd ed.). Prentice Hall. 7. 211-12

And of course, there are many similar examples throughout the book. I literally just opened it to a random page, and found that example.

At some point, the refrain of "Non-predictive! Just-so story! It's a pseudoscience!" starts to look like motivated cognition.

Buller claims that the statistics come from police reports and that the police had previously been trained to look for stepparents as a source of child abuse. If so, 1 this was well known by nonpsychologists and 2 the magnitude of the effect may be overstated. Is there a problem with this critique?
For 1, how is that a even critique? Is it possible for psychologists to have failed to understand something that cops understood? It doesn't even seem surprising that police, who have generations of practical experience dealing with abuse would notice the trend before ivory-tower academics. As for 2, I don't think that suggests the effect is overstated, except maybe very weakly. The effect is so huge that it's hard to believe that police suspicion of step-parents can "explain it away".
Here's a case of confusion. Isn't this conjecture obvious? Cinderella? Beaten like a red headed stepchild? I'll take it as more likely that an evo psych researcher pointed out the obvious, than an evo psych researcher pointed out the obvious because of his evo psych theory.

Some lazy googling indicates the phrase "beaten like a red-headed stepchild" was raised to contemporary popular consciousness in 1986's "The wrath", years after Daly and Wilson. Originally it was racist, specifically referring to the way one might treat the result of a wife's earlier dalliances with Irish immigrants.

I'm not sure I trust my intuitions about what an average high school dropout could tell me in the 1970's. But I consider it significant that professionals looked into this question, and did not notice that factor previously, an unlikely result if it was both widely known and actually present.

I suspect this may be a case of the professionals not wanting to notice because they didn't want to seem politically incorrect.
The time prior to the Daly and Wilson paper (1980) included a lot of time when modern notions of political correctness were not operative.
I think you're right. It is usually best to conform and be politically correct in most cases, biding time until there is a specific issue on which you can make a stand with an expectation of significant benefit to yourself or your objectives. Choosing a battle.
One would hope so! But I reject (what seems to be) the intended connotation - that having an evo psych theory would not have a dramatic influence on the probability that a prominent researcher would point out this particular instance of the obvious. It may be useful to focus on the 'pointed out' part. Even allowing that a fact is 'obvious' enough that it occurs to everyone, when it comes to pointing things out - particularly in the form of presenting it in a formal research context - incentive matters. Most people who have proven their ability to gain academic credibility are wise enough to not go around making controversial claims unless they have a personal stake in it. Their intellectual territory must somehow be expanded by the pronouncement. An evo psych researcher potentially gains status by showing a new area where his theory can claim authority. A non-evo psych researcher is less likely to gain from spouting step-parent risk factors. He or she may even benefit from rejecting the step-parent influence in order to support an entirely situational based model of social behaviour. Whatever it takes to make the situation look more like the kind of 'nail' that their clique's 'hammer' is built to handle.
I rather agree with you fully, but you are elaborating 'because of his evo psych theory' differently than I intended. The OP's point appears to be that no one [or at least expert] was aware of the connection, until evo psych created a framework that generated a prediction along those lines, that then allowed people to begin focusing on that connection. That's the sense I used. Your political story, along the lines of gravestone to gravestone, I find reasonable and likely.

Much of the commentary here has turned into yet another debate about just how useless and unscientific evolutionary psychology is. (Notice how I cleverly signaled my own viewpoint about the debate. :) But do we really need to have this debate?

It occurs to me that Luke's argument (about the misuse of intuitions by philosophers) really is independent of whether present-day evolutionary psychologists know what they are talking about. All Luke's arguments, if I understand them, really need is that some intuitions are innate and derived from our evolutionary history, some are learned, and that some are generated on the spot by fallible cognitive processes. It really doesn't matter whether an innate intuition arises as an evolutionary adaptation or an evolutionary accident - it still doesn't provide a philosopher what he needs to ground his arguments.

If I am right here, and the validity of evolutionary psychology is irrelevant to Luke's arguments, then lets move on. We can debate whether the validity of evolutionary psychology is irrelevant more generally at some other time.

I endorse all of this. As for your comment below about how I "seemed to suggest [evpsych] was the best thing since slided bread," I'm not sure where you got such an idea. Evpsych is, as others have pointed out, full of holes. I pointed to some of those holes in my first footnote.
Other people who talk about evo psych think it is the best thing since sliced bread. You talk about evo psych. Therefore, you think evo psych is the best thing since sliced bread. It is approximately the same intuition at play as that which you describe as 'essentialism' - and nearly ubiquitous when speaking with humans. If you say something about a topic or theory you can assume that you will be judged according to whatever other people who talk about the same topic, position or theory have said.
It's also a perfectly valid piece of Bayesian reasoning.
It isn't if it is made as a logical deduction - as it was presented in the quote and also how it is frequently implemented in practice. The valid Bayesian reasoning would be a well calibrated calculation of the probability that the speaker happens to think those same thoughts given the remembered behaviours of other individuals of the same species. If only that was how humans behaved!
Supposing that the dispute is tangential to the topic of the article, I've seen many such disputes arise in comments without their digressiveness being raised as an objection. Is your concern that you think this threatens to overwhelm the main topic?
No, actually I'm not all that concerned. Mostly, I just wanted to point out just how low the stakes are in the often-heated arguments about evopsych. Luke wrote about evopsych, and seemed to suggest that it was the best thing since sliced bread, but it often seems that the people who praise evopsych (but don't have a particular just-so-story in mind) really aren't interested in the actual explanations that evopsych offers; instead they just are pleased to be able to stick pins into the inflated and self-congratulatory views of human nature which arise from non-evolutionary accounts of our origins.
That makes it sound as if the evopsych controversy is evolutionists versus creationists. My impression was that it's mainly naturists versus nurturists.
You may be right, but if so, that paints a pretty dismal picture of the current state of psychology and anthropology. If you want to determine whether some human trait (a propensity toward alcoholism, say) is a result of nature or nurture, inventing competing just-so stories about the origin of that trait is a pretty poor way to decide between the hypotheses. And if you already know that a trait is innate, a disputed evopsych explanation brings nothing extra to the party.
What it does do is tell you what to bring to the next party and perhaps a hint as to what to do about the hangover the next day. Improving our model of how the traits that know about evolved allows us to form better hypothesis about what other traits may be present and worth investigating. It could also suggest avenues for research in the area of physiology. Knowing why something exists can give some clues about how to go about fixing it when it is broken. Plus... I like to know stuff! Causes intrigue me. Raw lists of correlations are dull.
Ok, but I don't see how that is responsive to my point. Which was that you really ought to determine whether something is innate or learned before you begin generating hypotheses as to just how it became innate. That is, determine the proximate cause first, then go to work on other kinds of causation. ETA: Btw, it is "group selection", not "group evolution". ETA#2: Ah, if you didn't realize that the 'party' in question is the nature/nurture debate, then you would think that you were being responsive. Kindly ignore the snarkiness.
I had assumed that I made a slip of the fingers but looking back I don't seem to have used that phrase at all. Was that me or someone else you were referring to?
It was you and then Matt_Simpson and then you again. But it seems to have died out now.
Ahh, I see. in the first context it was 'group selection' that the researches intended to facilitate but not what actually occurred. The resulting outcome was instead individual selection being the dominant factor in how the groups evolved. This is to say that 'group' and 'evolution' are used correctly as independent terms, not as a phrase referring to a single construct. The latter two should be 'group selection' so I corrected my follow up there, and the Matt quote with suitable edit-brackets to maintain the consistency in reply.

It is cheating to make predictions that are actually postdictions. To test hypotheses we have to look at questions for which we don't have information and then test those questions by gathering new information. A lot of the "evolutionary psychology" are really "Just So" stories without this kind of hypothesis testing.

A huge amount of science operates on postdictions. That's not 'cheating', it's just not as impressive as Einstein predicting gravitational lensing. Just as in other sciences, including evolutionary biology, evolutionary psychology uses multiple converging lines of evidence to weigh the probabilities of hypotheses (see, e.g., Buss, The Handbook of Evolutionary Psychology, pp. 457-465: PDF).

And in fact, evolutionary psychologists often do make novel predictions and then go out and make the observations that either confirm or disconfirm the hypothesis.

I suspect that those who say evolutionary psychology is nothing but 'just so' stories are not actually keeping up with the science but instead are operating under cached thoughts.

Ok, update my cache: you listed 7 bold postdictions; please list some bold predictions. Its true that not all science is prospective, but you need to at least avoid looking at the data when making hypotheses you will then test against that data. Often we divide a data set to do this. Its much easier to do this with quantitative hypotheses than qualitative ones.
Here are some additional predictions from evoutionary psychologists.
The first two are excellent examples. Thanks!
Wasn't there a talk that touched on this at the last Singularity Summit? John Tooby IIRC. I don't remember if it was during his talk, the panel discussion, maybe his Q&A... I'm fairly certain at some point he (or someone) named a couple of big predictions. I'll look this up tonight unless someone beats me to it. Edit: Here is what I was remembering. He talks about his guide to generating good psychological hypotheses through awareness of evolution at 15:00, with a slide with the 5 step plan at 16:40. His primer on evolutionary psychology is here and has an interesting example of a prediction of cheater detection at the end.
knb provides one example here, though I can come back add others later. Highly relevant is this post from Yudkowsky.
If Buller is to be believed that's another postdiction. The sort of studies I want to see would compare two groups who aren't known to be distinct. An example: Group A and B evolved in different environments and should display some difference in behavior. They have different rates of intron fragments G and H Now look at apparently-homogenous group X, who do not believe they have A or B ancestry. Compare X with intron G to X with intron H and find the predicted behavior difference. Do we have studies at that level?
The same thing was true of Darwinism before molecular biology. So you would have advised those biologists before 1950 not to believe in the theory of natural selection until it had made predictions that are not postdictions?

Evolutionary psychology also clearly explains why a significant portion of the human population will be homosexual.

Oh, wait. It does the exact opposite of that. Hmmm. [ETA: I admit kin selection provides a basis for saying that homosexuality might kinda not totally be evidence against the genetic origin of certain traits. It's not the kind of thing that anyone would predict if they hadn't already seen it, and my main point is about ex post rationalization.]

I certainly agree with the general conclusion that natural selection and our specific history as soci... (read more)

You should try googling ' "evolutionary psychology" homosexuality'.
Still, it seems unlikely that if we did not observe homosexuality, researchers would be stroking their chins and saying, "Hmm, we should figure out why there is no large minority of our population that is exclusively attracted to members of the same sex. I mean, isn't that weird? How would that sort of thing evolve?"
This is a really important principle. You haven't explained a thing if you wouldn't be confused by that thing's absence. ETA: This point is very similar to one of Eliezer's observations: There is a subtle distinction, though. In that post, the emphasis is on noticing when your theory contradicts a reported fact. Eliezer points out that you should either modify your theory or deny the reported fact. You shouldn't fall into the common failure mode of concocting some improbable scenario in which the fact could have occurred without contradicting the theory. I take Alicorn's point to be about noticing when your theory neither contradicts nor implies a reported fact. The emphasis here is on avoiding the failure mode of convincing yourself that the reported fact is just what you would expect to happen, given your theory.
Very true. However, my point was more that this doesn't exactly conflict with evopsych either. Of course, the question if evopsych actually does any useful predictions is still open. :)
I just did that, and while there are a lot of hits, I did not find anything but speculation on the matter. For example, this was the first freely available scientific paper I found on Google Scholar addressing the question. I looked at a few others but they were much the same. There are many speculations -- it would be too much to call them theories -- but if there is actual evidence settling the matter, or even just substantially favouring some hypotheses above others, I did not find it. On the wider internet the first two hits are junk. Seriously written, but junk. The third reports a test of the theory that homosexual men provide extra care for their relatives. It finds that in the one culture studied such an effect is present but not enough to offset the evolutionary cost of not reproducing oneself. The fourth reports another test of the kin support hypothesis, that failed to support it. So, I have looked, and found no successful evolutionary explanation of homosexuality. Did you have some expectation about what that Google search would find, or were you just suggesting that it would be informative one way or another on the subject?
The only theory I've seen that makes any sense is radioactive politically. Pathogenic Hypothesis of Homosexuality An Evolutionary Look at Human Homosexuality
You may already be aware of these papers by Andrea Camperio-Ciani. The first one made a pretty big splash a few years back. Certainly not evolutionary psychology - just good old fashioned genetics (pedigree analysis). And not an explanation of why homosexuality evolved, but a plausible explanation of why natural selection has not ruthlessly eliminated it. To my mind, the big problem with evolutionary psychology is that it displaces this very straightforward kind of science. It achieves success, not by finding truth, but rather by finding an appealing story. Kinda like religion.
To my mind, the big problem with evolutionary psychology is that it tries to boil everything down to advantages to DNA - and usually pays insufficient attention to the possibility that memes are what have benefitted instead.
To put it mildy: I did not think this was a good argument.
Touche. It is possible to explain almost anything ex post. Moreover, it's really unclear (and what I've read does not address) how a gene that causes someone to not reproduce gets passed on. Assuming that just you have the gene and your relatives don't, it's beneficial. But if you all have the gene, that's a very different story. A gene that causes me to sacrifice myself to save my brothers is conditional - it doesn't matter unless the need arises. A gene that causes me to prefer non-procreative sex doesn't seem conditional in the same way - it simply prevents me and anyone who has it from reproducing. In short, while one can rationalize the behaviour as advantageous ex post, it's rather hard to actually put that together cogently, and it's a very long way from getting rid of, "largely accidental" as an alternative explanation. I will admit bias on this issue, having dated a woman with a lesbian identical twin.
Homosexuality could be controlled by environmental factors and appear at a good rate for kin selection while being genetically present in more people. Here's a more straightforward fictional example: In Elcenia, there's a type of natural magic-user called "lights". They have healing magic - really heavy-duty healing magic, equal to or better than modern Earthly care in most respects and infinitely cheaper. However, lights can't heal themselves or each other, so it's not such a great thing to be a light - you're much more likely than the people around you to die of disease or injury. But it's really, really useful to have a close family member who's a light, because they'll heal you when you get sick or hurt. So what happens in practice is most people in species where lights appear have the necessary genetic component, but only about 1-2% of the population depending on region encounter enough ambient magic in the womb to turn into actual lights.
I get the underlying theory just fine. It's a neat fictional example, but (and I'm not familiar with the underlying fiction) it would probably be extremely fitness-enhancing. A male light would probably be incredibly high status and have little difficulty producing offspring. If it were purely genetically determined, it seems like it'd be pretty hard to sustain - no one would want it for their own children. If it were recessive, it might work out better, but there still seems a substantial problem of free-loading. Thus, this evolutionary explanation for homosexuality partly undermines itself: it's genetic, but it's not quite genetic and there's other stuff going on that determines whether or not it gets activated. So it's either genetics (actively-selected) + environmental factors or genetics (random noise) + environmental factors. That's not a very clear case for kin selection, to say the least. My claim isn't that it couldn't possibly be related to kin selection. It's that, like many ev-psych claims, the evidence for "or something else is going on" is far too strong to make a definitive claim, particularly because the outcome is the exact opposite of what you'd expect from simpler evolutionary theory. Otherwise, you risk combining two theories in a way that can explain far too many outcomes. Any individual who fails to reproduce can divert resources to his siblings. You could just as easily say many negative traits that don't show up with absolute consistency are also advantageous. This seems like a stretch. In retrospect I will admit that this example detracted from my overall point and was poorly chosen.
That... has a lot of potential.

Haven't read the post yet, but reporting an odd interface behavior:

When I follow links to this post from the "recent posts" sidebar, it works fine

When I follow links to this post from individual comments in the "recent comments" page, I get a "Forbidden" page. The url is different in this case as well: rather than This is true for both recent and early comments.

Links to other posts from individual commen... (read more)

Please submit a bug.
Hey, look at that! Thanks. Done.
Bummer. Anybody know what's up with that?

For example, it seems unlikely that we evolved a mechanism that gives us reliable intuitions about the metaphysical possibility or impossibility of zombies.

It's outside the scope of your article, but one thing that I find curious is that people nonetheless do have strong intuitions about philosophical questions for which natural selection wouldn't instill an intuitive answer. Since these intuitions aren't shaped by natural selection, different people, even within the same culture, can have very different intuitions on the same question (e.g., A-theory ... (read more)

Heuristics and biases

Human reasoning is subject to a long list of biases. Why did we evolve such faulty thinking processes? Aren't false beliefs bad for survival and reproduction?

Many researchers suggest that while humans are poor at formal logic and Bayesian inference, humans display a kind of 'ecological rationality'.

Other researchers think that our rationality is a direct result of our need to convince others that we're right, and that many of our biases (e.g. confirmation bias) are a direct result of this.

Edit - please disregard this post

It seems to me the idea that essentialism evolved for dealing with creatures is a bit too narrow; certainly we don't use it just with creatures, and to the extent it works it does work more broadly than that. I would expect it would more have to do with general factors like speed and scalability (as Eliezer points out in Neural Categories).

The link in "And no, evolutionary psychologists do not only offer 'postdictions'..." is broken.

It looks like this might be it:

typo?: "If the hypothesis is could correct"

Fixed, thanks.

Even someone who has read Richard Dawkins rant against essentialism

This is kind of a jarring use of the word "rant". Dawkins's argument seems calm and well-reasoned. (Except where he says "Indeed, every one of the series was the child of its neighbor on one side and the parent of its neighbor on the other...". Wouldn't there be at least one animal in the series who was the parent of both its neighbors?)

Okay, fixed. 'Rant' doesn't have a negative connotation for me.
Thanks. I should have mentioned that this article is yet another excellent contribution from you, notwithstanding my petty nitpicking.

Heuristics and biases

Human reasoning is subject to a long list of biases. Why did we evolve such faulty thinking processes? Aren't false beliefs bad for survival and reproduction?

Given the nature of evolution and the fact that perfect Bayesianism is computationally intractable, the thing to be explaining is not how bad our reasoning is, but how good it is.

I'd say there is time to do both. When looking at biases I find it useful to distinguish between the ones that are the outcome of our reasoning 'just not being good enough' and those where sound reasoning appears to be actively sabotaged. Those cases where evolution spent extra optimization power introducing mechanisms that hinder the formation of correct beliefs due other selection pressures. Of course we can also spend time explaining how good human reasoning is, either for the sake of saying "Rah! Humans" or for the purpose of developing our own optimisation processes. The two quests for knowledge are hardly mutually exclusive.
Pompomtime! Go, Humans! Hehe. We'll need to know both to decide just which biases we want to keep, if any. Edit - please disregard this post

As Eliezer demonstrated in this example here what you call Essentialism doesn't just apply to creatures.

And as it turns out, all these predictions are correct.

Sarcasm, or accidental humor?

This is a good explanation for (some of) the lack of progress in philosophy.


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