The human cortex, responsible for complex thought
and reasoning, is overgrown in humans when compared to other mammals.
Scientists have argued for years about why this is the case.
One theory holds that our brains evolved because
our primate ancestors began to gather food in more complex ways.
They began eating fruit instead of grasses and leaves. This involved
traveling long distances to find food, and required each species
to maintain a complex mental map in order to keep track of fruit
trees. More brainpower might have been needed to determine if a
fruit was ripe, or to discern proper methods for peeling fruit or
The problem with this theory is that if one tries
to match brain size with the eating habits of primates, it doesn't
work. Some small-brained monkeys are eating fruit and maintaining
complex maps and some larger brained primates are eating leaves.
What does work, apparently, is group size. If one
examines any species of primate, the larger their neocortex, the
larger the average size of the group they live with.
Anthropologist Robin Dunbar has done some of the
most interesting research in this area. Dunbar's argument is that
as brains evolve, they become larger in order to handle the unique
complexities of larger social groups. Humans socialize the largest
social groups because we have the largest cortex. Dunbar has developed
an equation, which works for most primates, in which he plugs in
what he calls the neocortex ratio of a particular species - the
size of the neocortex relative to the size of the brain - and the
equation gives us the maximum expected group size for each species.
For humans, the max group size is 147.8, or about 150. This figure
seems to represent the maximum amount of people that we can have
a real social relationship with - knowing who another human is and
how they relate to us.
Dunbar has gone through anthropological literature
and found that the number 150 pops up over and over again. For example,
he looked at 21 different hunger-gatherer societies around the world
and found that the average number of people in each village was
The same pattern holds true for military organization.
Over the years, through trial and error, military planners have
arrived at a rule of thumb for the size of a functional fighting
unit - 200 men. They have realized that it is quite difficult to
make any larger a group than this to function as a unit without
complicated hierarchies and rules and regulations and formal measures
to insure loyalty and unity within the group. With a group of 150
or so, formalities are not necessary. Behavior can be controlled
on the basis of personal loyalties and direct man-to-man contacts.
With larger groups, this seems impossible.
Further is the religious group known as the Hutterites,
who for hundreds of years, through trial and error, have realized
that the maximum size for a colony should be, low and behold, 150
people. They've been following this rule for centuries. Every time
a colony approaches this number, the colony is divided into two
separate colonies. They have found that once a group becomes larger
than that, "people become strangers to one another." At 150, the
Hutterites believe, something happens that somehow changes the community
seemingly overnight. At 150 the colony with spontaneously begin
dividing into smaller "clans." When this happens a new colony is
Another good example of our hard wired social limits
is Gore Associates, a privately held multimillion-dollar company
responsible for creating Gore-Tex fabric and all sorts of other
high tech computer cables, filter bags, semiconductors, pharmaceutical,
and medical products. What is most unique about this company is
that each company plant is no larger than 150. When constructing
a plant, they put 150 spaces in the parking lot, and when people
start parking on the grass, they know it's time for another plant.
Each plant works as a group. There are no bosses. No titles. Salaries
are determined collectively. No organization charts, no budgets,
no elaborate strategic plans. Wilbert Gore - the late founder of
the company, found through trial and error that 150 employees per
plant was most ideal. "We found again and again that things get
clumsy at a hundred and fifty," he told an interviewer some years
Take a lesson from this. If you are engaged in a
large enterprise or are planning to work for one, realize that large
groups rapidly reduce the efficiency of an operation. If each department
is separated, especially if there are hundreds or thousands of people
involved, complex systems of organizations will be required to keep
everyone in check. Peer pressure is much more powerful than the
somehow vague concept of a boss or punishment. People will work
only hard enough not to get fired in a very large group, but will
live up to the expectations of their peers in smaller groups where
they have a personal relationship with each of their co-workers.
Of course, a small group size is not by any means a guarantee of
success. Small enterprises fail all the time. It's just a concept
-- an idea to keep in the back of your mind as you vegetate in that
For more information:
R.I.M Dunbar, "Neocortex size as a constraint on group size
in primates," Journal of Human Evolution (1992), vol.
20, pp. 469-493.
Dunbar has also written a good many spiffy
books of which I would recommend:
Gossip, and the Evolution of Language.