our species is endowed with a unique and extraordinarily powerful adaptive
mechanism: “collective learning.” That’s a term I’ll use a lot so I need to
explain it carefully.
Adaptation by natural selection is slow. Because it depends on genetic
changes, it can take hundreds or thousand of generations for changes to
evolve and spread. But there are other ways of adapting. Organisms with
brains can change how they relate to their surroundings within a single
lifetime. This is “individual learning.” It works faster than natural selection,
but it has limitations. Individual learning is costly because brains consume
lots of energy and have to be fed. Emperor Hirohito, who was a biologist,
once studied a species of sea slug that illustrates the point nicely by eating its
brain once it no longer needs it. Individual learning is not cumulative. Most
of what an individual learns cannot be passed on to others, so each individual
has to start from scratch.
Now imagine a species in which individuals could pass on most of what they
learned to other members of their species. Here we would have a third, and
much more rapid, way of adapting—because what each individual learned
would then be stored within the entire community. This is the unique gift
humans acquired with human language. Simple forms of communication
depend on one-to-one correspondence, like the warning call of a vervet
monkey: A bark-like call means a leopard, while a sort of stutter means a
snake. Such utterances can communicate about as much information as an
ambulance siren. Most animal languages seem to take this form.
However, humans are capable of using “symbolic language.” Symbols are
arbitrary signs that can group many observations or ideas within larger
categories and can therefore rearrange information in many new ways. While
a vervet can say “leopard,” it cannot say exactly where the leopard is or what
it is doing. Symbols can convey such information. They can even refer to
things that are not present (such as the leopard I saw yesterday) or things that
may not exist (pink elephants or Santa Claus).
Human languages also have elaborate grammatical systems that greatly
enhance their ef¿ ciency. Grammar lets us arrange symbols in almost in¿ nite
con¿ gurations so humans can use word pictures to convey large amounts of