Hi there, everybody!
Today we’re here to talk about Dunbar’s number.
Oh hey, look who it is, renowned British anthropologist and evolutionary psychologist Dr Robin Dunbar,
himself.
Hi Dr. Dunbar!
How’s it going?
“YU KIN ONLY ‘AVE 150 MEANIN’FUL CONNECSHUNS WIF PEEPUL!!”
Uh… yeah, right!
We were just about to talk about that.
Why don’t you tell the audience how you figured out that number?
“‘OW DO YA FIGYA ANYFING OUT??
I LOOKED AT SOME MONKAY BRAINS!”
Uh…
Right.
Yeah.
Well, bye Dr. Dunbar.
“SEE YA’ ROUN’, GUVNAH!”
So, as you may know, primates have unusually large brains relative to their body size—much
bigger than any other animal group—but why did primates decide to become such colossal
nerds?
Well there are some theories involving nutrition and digestion and stuff, but those are boring
so instead let’s focus on the one that sounds like it’s from a Marvel comic, the “Machiavellian
intelligence hypothesis,” which essentially posits that primates developed increasingly
big brains because those gave them an evolutionary advantage in developing complex social strategies
to achieve higher reproductive success.
Basically, bigger brain, better at manipulating others, more reproduction, something something
Darwin something.
In 1992, everybody was bored because they hadn’t invented making fun of Elon Musk
yet, so Robin Dunbar decided to look at the ratio of neocortex size to total brain volume
for different types of primates, and then compare that to the size of those primates’
typical social groups.
When he did, he found a pretty clear correlation: the bigger the neocortex to brain ratio, the
larger the size of a social group.
By extrapolating that relationship to a human brain, he found that humans should have an
average social group of 148, but then he rounded it up to 150 because that sounds better in
a Malcolm Gladwell book.
Now if you’re just a regular, normie not-anthropologist, you’re probably wondering, “A social group?
What does that mean?”
Well, in his book, Dunbar explains the 150 number in a very concise, very precise, very
scientific way as “the set of people who, if you saw them in the transit lounge during
a 3 a.m. stopover at Hong Kong Airport, you wouldn’t feel embarrassed about going up
to them and saying, ‘Hi!
How are you!
Haven’t seen you in ages!’
In fact, they would probably be a bit miffed if you didn’t.
You wouldn’t need to introduce yourself because they would know where you stood in
their social world, and you would know where they stood in yours.
And, if push really came to shove, they would be more likely than not to agree to lend you
a fiver if you asked.”
For short, though, you can call them PWIYSTITTLDATAMSAHKAYWFEAGUTTASHHAYHSYIAIFTWPBABMIYDYWNTIYBTWKWYSITSWAYWKWTSIYAIPRCTSTWBMLTNTATLYAFIYA.
And it turns out that if you look, you’ll see
the number 150 all over the place.
Ford trucks, signs between 149th and 151st street, and if you google “what’s two
times seventy five.”
But we also see it in naturally-occurring human groups.
There were basically three groups sizes in pre-industrial, human hunter-gatherer society:
temporary night camps, which had 30-50 people, and were generally unstable, with people constantly
coming and going.
Large tribes, of about 500-2500, but those were mostly held together by language and
cultural identity.
In the middle, though, we find clans: groups with “ritual significance.”
In some cultures, it’s the group that would, for example, be present at a “coming of
age” ceremony.
One interpretation of clans is that they were essentially someone’s social group.
For the 20-ish tribal societies with census data, when we look at clan sizes, we find
a mean of 153 people, which as you might notice, is only about four more than 150.
And that’s just one of many examples: Neolithic villages in 6000 BCE had about 150 people,
and William the Conqueror’s Domesday Book from 1086 shows that 11th century English
villages averaged around 150.
In the modern day, although we’ve moved past the need for many old, naturally human
things, like hunting for food, or dying of dysentery, we seem to have kept the 150-person
grouping around.
Religious commune societies like the Hutterites and Amish tend to sit at around 110 people,
and split once they pass 150.
The smallest independent modern military unit, the company, is typically three 30-40 person
fighting platoons, plus command staff and support units, which adds up to about 150.
Factories of the company Gore-tex were famously kept to 150, as Mr Gore found that once they
got larger they required inefficient hierarchies.
And one experiment even found that people send Christmas cards to roughly 68 households,
which consist of about 150 people, because nothing says “you’re a valued member of
my social group” like a glossy 4x6 of your family looking uncomfortable in matching pajamas.
Dunbar’s number may be 150, but it turns out, one other number he knew was 5, which
Dunbar called the “inner circle,” the rough number of close contacts with whom people
tend to talk at least every week—presumably before Snapstreaks became a thing.
In fact, Dunbar identified a number of distinct social circles, grouped in increasing factors
of 3.
There are about 12 to 15 people in what social psychologists often call the “sympathy group”
which is defined as “people whose death tomorrow would leave you distraught,” which,
ah, super chill definition, thanks social psychologists.
We tend to talk to them at least once a month.
Interestingly, 12 to 15 is also roughly the number of people on team sports, juries, and
groups of apostles, although about 1 in 12 apostles tend to betray you, so watch out
for that.
If you go up another factor of 3, that’s your “affinity band,” about 50 people
who you would still consider real friends, and talk to once or twice a year.
Going past Dunbar’s number, at 500, we reach your approximate number of acquaintances,
and at 1,500, you start to bump into the limit on the number of people you can actually recognize.
Past 1500, we start to get into strangers, and you know what strangers love to do?
Monitor your internet activity.
Let me ask you a question: did you know that a lot of ISPs monitor and keep logs of every
website you visit, even when you’re in incognito mode?
Now let me ask you another question: do you wish there was a way to make them not do that?
And now here’s a third question: have you figured out yet that this is all a lead-up
to telling you why you might want to use ExpressVPN, which encrypts your data and reroutes it through
a secure server so that your browsing stays private?
I’ve used ExpressVPN for years, both to keep my data secure, and to do some of the
other fun things a VPN lets you do, like accessing international Netflix libraries, and streaming
region-restricted sports and games.
For example, you could watch this indie workplace comedy, which is still on Netflix UK.
If you, like me, enjoy the feeling of not being spied on, try out ExpressVPN, and you
can get three months for free by going to expressvpn.com/HAI.