Posts tagged with zebras

Another reason for economists to take a close look at inequality, social rank, envy, greed, dreams, social or cultural messages/expectations, and so on as determinants of experienced utility.

Sapolsky’s observation is that human beings engage evolutionary stress hormones in response to purely psychological stimuli. Looking at babboons, who cause each other stress as we do, he finds that lower ranked (submissive) males carry higher amounts of epinephrine (adrenalin) and glucocorticoids than dominant alpha males. (No reports in this documentary on fat-shaming or that ugly females have higher stress.)

So that may be a basis for thinking that social inequality—where a rank and a distance exist—really does mean a lower quality of life for the bottom-rungers, even if they have an absolutely high standard of living. (Sapolsky remarks that in the park he visits, food is so plentiful for the babboons that they only need to work 3 hours a day to survive. So they could be said to have an absolutely high wealth.)

Of course the “right” use of Pareto optimality always took into account the possibility that giving more money to Bill Gates could make me more miserable—but utility is so hard to pin down that a social-optimality conversation can easily be turned by “Well, it’s wrong of you to envy the rich” — casting aside the normative/descriptive distinction.

My first thoughts leap to envy-free solutions of pie-splitting problems (S J Bram, P C Fischburn)

image image image image

but maybe there are some free-lunch alternatives as well. Such as, is there something I’m doing that makes other people feel ashamed or stressed? Some subtle pitches to my voice or subtle movements of my eyes when I’m internally judging someone but trying to not say anything out loud? Why do I care anyway if some hippie wants to be an organic farmer and not get a job? I don’t think I even have a good reason to care; “ideological opposition”. Maybe you can make some arguments sometimes that I should be stressed about the possibility that my government gets overrun by a bunch of irresponsible ideologues and it’s worth the time to debate about it. Fine, but still maybe there are some free lunches in just not socially shaming other people. Just because I have more money doesn’t mean I need to look down on you as less a person. There certainly are narratives that tell that story—"Contribution to society" type narratives or "Hard work" narratives and sometimes even Smart narratives. But I don’t need to embrace those, especially if it’s suboptimal.


Minute 28 they show pictures of monkey brains lighting up in the pleasure centre or stress zones.


Making me think again of taking an integral of the chemical flows over someone’s life (how to deal with time I don’t know) as some kind of selfish evaluation of the pain/pleasure experienced over the lifetime. The naïvest thing would be to measure dopamine and integrate it up over time, perhaps convolved with a risk preference function, anti-variance or pro-variance preference, and some time preference (either NPV/Ramsey or work hard in youth for a delightful old age). Something more realistic would have to take into account that a full life should experience a variety of emotions and corresponding chemical combinations. When your father dies you don’t want to go on smiling and partying, for example.


Minute 48 we get Sapolsky’s interpretation: rank isn’t necessarily it, but rather what rank means in your culture. And our own psychological freedom to decide which hierarchy we think is important. Maybe, RS. Just because I have free will doesn’t make me Herculean, it depends how hard it is to override the bad thoughts with self-affirming thoughts.

Giving rather than receiving. Ask a middle-class parent if s/he is looking forward more to giving something to their child or receiving a present from a friend, partner, or coworker this Christmas? Yet the economics 101 just takes consumption and leisure as life’s desiderata.

So put this together with Daniel Kahneman's supposed finding of an “enough” level (around $45k for Americans I think) above which extra income doesn’t add very much to one’s sense of well-being.

That is, above $45k suponemos que income sea more of a ranking tool or a “You did right” reward. People’s happiness se determine más por the way coworkers and people around them act toward them [do I have to deal with this stressful person today? Does Mr Z laugh at my jokes? Do people look and speak to me as if I’m respectable, smart, admirable, good-looking, sexy, competent, fun, nice—what kind of person am I? Am I good?


] y menos por consumption por sí. Their home is comfortable enough, their food is good enough, life is easy enough. Money removes discomfort rather than providing happiness, kind of idea.

Hat tip @ArcAldebaran.

This has confused me ever since I learned about evolution.

As Mr. Shepherd explained it to me in the second grade, zebras are hard to kill because, when the zeal runs, their collective stripes make it hard for a predator to visually pick out an individual zebra to tackle.


So the benefit of stripes comes from

  • high contrast
  • highly structured shapes
  • in a group

In economic terms, increasing returns to scale — and increasing returns to coördinated group action (“Let’s all be stripey”).

coördination games

COÖPERATION by Selfish Genes?

So how can that process get started, if the returns to stripes don’t pile up until you get to a really high level of contrast, a very certain structure, and group coördination? Even with a constant scaling factor, how could genes that promote themselves, inside an individual zebra, coördinate to get many zebras to all adopt stripes at once?


It’s not like genes can talk to each other. How could they have coöperated to achieve a better group outcome? Humans do so with language. If there’s a fire in the building and everyone’s crowding the exit, someone can yell: “Stop! We all need to back up and wait in a line. Then we’ll get through this exit faster and all live. None of us will get through if we push each other.” But the genes don’t have a way to communicate for better group outcomes — right?

Maybe stripes could evolve if it only took a few mutations to turn on high-contrast stripes (then the possibility of coöperation arising randomly would be greater … but still small). But I also wonder if there isn’t a population dynamics answer. Or a game theory answer. Is sexual selection involved? Is the sexual transfer of genes involved?



I think about evolution in an abstract way. Even though I know there’s meiosis and specific proteins and RNA’s change the expression and so on, … I just think about genes-as-strings. They mutate and cross-pollinate, with the sexier strings pollinating more. Nature selects (in a Brownian manner) from the pool for the next generation.


Does anybody know a good book or paper about the mathematics of sexual selection, like in a dynamical systems model? Or some other explanation for how the zebra got its stripes?



Readers answered with a lot of mathematical biology links (great!). As I read through what they’ve sent, I’ll add to this list:

  • The pattern of zebra stripes is fully determined by day 21-35 of embryonic development (out of a year-long gestation). Melanoblasts mark out the patterns on the zembryo. Turing Patterns in Animal Coats, via Artemy Kolchinsky