The Meme Machine

72 THE MEME MACHINE
and ability to hold down a job were ruined, he could still walk and talk and, at
least to some extent, appeared normal. The same is true of the victims of frontal
lobotomy, a crude operation that destroyed parts of the frontal cortex and was
once used to control serious psychiatric cases. They there never ‘themselves’
again but the changes were subtle considering the vast amounts of brain damage
caused in this horrible ‘treatment’. There are numerous theories of the function
of the frontal lobes but none is universally accepted. We cannot find out why
our large brains evolved by appealing to the function of the part that was
enlarged the most.
Apart from the massive increase in the frontal lobes, the brain has been
reorganised in other ways. For example, there are two main cortical areas that
are critical for language, Broca’s area which is responsible for speech
production, and Wernicke’s area which is responsible for language
understanding. Interestingly, these two areas seem to have evolved from the
motor cortex and auditory cortex, respectively. Most sounds made by other
animals, from grunts to calls and birdsongs are produced in the midbrain, by
areas closely connected to those controlling emotional responses and general
arousal levels. Some human sounds, such as crying and laughing, are also
produced by midbrain areas, but speech is controlled from the cortex. In most
people both of the main language areas are in the left hemisphere, so that the two
halves of our brains are not the same. Most of us are right-handed, meaning that
our left hemisphere is dominant. Although some apes show handedness most do
not and there is nothing like our systematic brain asymmetry in other primates.
Clearly, our brains have changed in many ways other than just size.
I have described very briefly what needs to be explained – that over a period
of about 2.5 million years hominid brains steadily increased in size, an increase
that carries obvious costs and must have been driven by a powerful selection
pressure. But we do not know what that pressure was.
Theories of the big brain
Theories abound. Most early theories suggested that toolmaking and
technological advances drove the need for a larger brain. For theories of this
kind the selection pressure came from the physical environment and from other
animals. Human brains were needed to outwit their prey. Tools provided
obvious advantages and bigger brains could make better tools. Among problems
for this kind of theory are that the increase in brain size seems to be out of all