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Dunbars number and other evolutionary quirks.

Our evolutionary history

Amazon review: 4 stars.

We are the the product of our evolutionary history, according to professor (of evolutionary anthropology at Oxford University) Robin Dunbar. According to Dunbar, the evidence is everywhere: From the way we socially interact (Grooming, laughter, music and language), to the way our minds are actually build and onwards to the way our minds are capable of reflecting about the world. There is an evolutionary hand in it everywhere. The book is a delightful and fascinating read, sharing insights from many fields, but always with a focus on evolutionary biology.


Grooming comes in many forms is not just about removing fleas. It is about intimacy, it creates a sense of wellbeing and relaxed connectedness. It has to do with endorphins. Indeed, mental stress and low-level pain is dealt with by the endorphin system. The physical stimulation of the skin triggers the release of endorphins in the brain. Endorphins are part of the body’s pain control system. Where pain thresholds are much higher if endorphins are released in the brain. It turns out that laughter is also an extremely effective releaser of endorphins. If you have just laughed a lot, then you have an elevated pain threshold afterwards [p. 69]. Laughter really is a medicine. Music also triggers the release of endorphins. Music also gives us a sense of wellbeing, contentednes, belonging and groupishness that is so important in the process of social bonding [p. 72] (Producing music obviously also have a sexual selection component, but this doesn’t take away from other functions). And there is more grooming…. Language is obviously also a sort of grooming: ”I find you interesting enough to waste time talking to” (and then of course you can even exchange information with language).

Grooming helps us survive both as individuals and as groups. And sex selects the desirable traits. Even though sex is a highly complex process… and, indeed, sex can be pretty confusing (…True, it is all about X and Y chromosomes. XX gives a girl. XY gives a boy. But accidents of genetics can give many other combinations: XXY, XXYY, XXXYY, XYY – and sure, most of these chromosome types are associated with serious disabilities and abnormalities, and most are rare. But they are out there. And it gets weirder. In turtles and crocodiles your sex depends on the temperature of the nest in which you were incubated as an egg. In some coral reef fish – everyone begins life as females, but if there is no male, the dominant female undergoes a metamorphosis and turns into a male [p. 98] …).

But, somehow, traits are passed down to the next generation. According to Dunbar, not in the simple ways you might expect. Indeed, we are not a random mosaic of bits inherited from our parents: It is not as random as we might think. It is not just: Half the population would inherit a particular trait from their fathers, and the rest would inherit from their mothers. According to Dunbar, it is a bit more complex. Instead, some bits are always inherited from the father, others always from the mother. And things gets very interesting in the brain. Dunbar quotes Barry Keverne and Rob Barton for a theory, where females have won the battle over control over (inheritance of) the neocortex, because social skills (which the neocortex controls) are more valuable to them, whereas males have won the battle over who controls the limbic system (manage fight or flight circuitry), because it pays not to think too much about what you are doing, if you get into a fight (The risk of injury or death is something the neocortex might come up with, but in games where second best means death, such cautious considerations are not helpful). The evolutionary battle of the sexes ends up being about control over the bits of the brain, though it is still something of a mystery as to how this is brought about [p. 15 – 17].

Put the process is evolutionary and it works rather fast. Think about Polar bears! Now, they might be snow white. But evolution works fast. According to Dunbar, it has taken only ten thousand years to produce the snow white bear from its common ancestor with other brown bears (Well, Wikipedia says the polar bear diverged from the brown bear, Ursus arctos, roughly 150,000 years [1] ago). Indeed, everything is quite new. Just consider humans. Some 100.000 years ago we lived in a world with many other species from the homo family. The last Neanderthals dies out some 28.000 years ago, The last Homo Erectus hominids dies out some 60.000 years ago [2]. And on Flores, Indonesia, a dimunitive member of the Homo Erectus family survived until as recently as 12.000 years ago. In Africa we were all black and as we travelled north we became white (It is not possible to travel so far south that it will make you white, but the Sand Bushmen of the Kalahari are certainly not as black as people from further north, like the Zulus, who arrived in souther Africa only a few hundred years ago).

In humans the game is all about giving us these spectacular minds that can do all of these amazing things, like reflecting on someone else’s mind. Intentionality is the capacity to reflect on the contents of one’s mind. As reflected in the use of verbs like suppose, think, believe etc. This is first-order intentionality. And most mammels probably falls into this category.If you are capable of reflecting on someone else’s mind state (I suppose that you believe) this is a second order intentionality. The stage children arrive at age 5, when they first acquire a theory of mind. Adult humans can aspire to fifth-order intentionality, but that this represents an upper boundary for most people: I suppose [1] that you believe [2] that I want [3] you to think [4] that I intend [5] . Intentionality provides us with a way for scaling cognitive abilities. And it turns out that these capacities are a linear function of the relative size of the frontal lobe of the brain.

Shakespeare was really good at this mind stuff. In Othello: Iago intends that Othello should believe that Desdemona loves Cassio and Cassio loves her. I.e. Shakespeare intends that the audience believe that Iago wants Othello to suppose that Desdemona loves Cassio and he in turn loves her. Which adds up to a six-order intentionality. Not only must Shakespeare handle this , but he is also pushing the audience to their limits forcing them to work at fifth-order intentionality. Obviously, a chimpanzee with cognitive limits set at second order intentionality could not have written Othello. And Chimpanzees don’t plan ps3 games like Drakes Deception ! 🙂

According to Dunbar, a lot comes from our spectacular minds. Take religion: Religion is also a complex cognitive structure. The system can only work if I believe that you suppose that there is a higher being who understands that you and I wish something will happen (intervention of some sort?). Thats a fourth order system just for starters, and to understand the system you quickly need fifth-order abilities. Indeed, religion is dependent on social cognitive abilities at the very limits of human capabilities. The benefits of religions are nevertheless obvious: a) A system (flawed, as sometimes it doesnt work) to predict the future b) Make us feel better about life c) Help us setup a moral code to keep social order d) give us a sense of group and community.

We have a come a long way: Homo Erectus had a skull size that two million years ago he could have inspired to third order intentionality (I believe that God wants us to act with righteous intent, personal religion). But social religion withis fourth-order intentionality comes later according to Robin Dunbar (some 500.000 years ago). And fifth order intentionality religion only with modern humans some 200.000 years ago. And who knows what the future will bring!?


Simon Laub

Categories: Uncategorized
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