The Meme Machine

THE BIG BRAIN 73
proportion to the scale of the endeavour. Big brains are so expensive that if you
could catch your prey with a slightly smaller one you would have an advantage.
Many pack animals hunt extremely effectively with brains that are small by
human standards. Indeed, as we have seen, it rather looks as though Homo
erectus began eating more meat to feed the growing brain rather than vice versa.
Something else must have been driving brain size.
Early hominids obtained much of their food by foraging. So perhaps a big
brain was needed for extracting difficult foods or for the spatial ability and
cognitive maps needed to find food in patchy and unpredictable environments.
However, animals with very small brains manage to store and find food in vast
numbers of separate locations, and many animals, such as squirrels and sewer
rats, make cognitive maps of large areas. Species with such good spatial skills
do show differences in brain structure but not in overall size. Also, predictions
concerning brain size and foraging range have not generally supported this kind
of theory (Barton and Dunbar 1997; Harvey and Krebs 1990).
Other theories emphasise the social environment. The Cambridge
psychologist Nicholas Humphrey (1986) suggested that early hominids took an
important step beyond their ancestors by beginning to look into their own minds
as a way of predicting what others would do. For example, if you want to know
whether that huge male gorilla is likely to attack you if you try to mate with this
attractive female, you should try to imagine what you would do in the same
situation. This introspection is the origin of what Humphrey calls ‘Homo
psychologicus’, of humans capable of understanding that others have minds, and
ultimately of self-awareness.
Consciousness itself is something we value highly and tend to think of as
uniquely human and special, but whether it provides any selective advantage is a
fiercely debated issue (e.g. Blakemore and Greenfield 1987; Chalmers 1996;
Dennett 1991). Some argue that consciousness could not have evolved unless it
had a function, while others maintain that consciousness is not the sort of thing
that could have a function. For example, if consciousness is an epiphenomenon
of attention or language or intelligence, then the selective advantage would be
for those capabilities, not for consciousness itself. More radically, some believe
that consciousness is an illusion, or that the whole idea of consciousness will
ultimately be dropped, just as the idea of the ‘life force’ was dropped when we
began to understand the mechanisms of life. Clearly, consciousness cannot help
us explain the big brain; you cannot solve one mystery by invoking another.