evolution of those systems,which is related to the evolution of encephal-
ization:enlargement of the brain in birds and mammals relative to rep-
tiles from which they evolved,and its further enlargement in the
evolution of these classes of vertebrates.However,the enlargement
called encephalization resulted from the increase in size in many differ-
ent specialized neural systems and is an aggregate enlargement within
which specialized increases are difficult to identify.
Falk’s efforts (this volume) to analyze neural correlates of the evolu-
tion of a Broca’s area in the frontal lobe of the hominid brain is the only
one that is directly related to this problem.However,it is difficult to sep-
arate her evidence of increased gyrification and the appearance of a
“third frontal convolution”in Homo habilisfrom the expected incre-
ments that would be correlated with increased brain size.The approach
is correct,however,in recognizing that the evolution of musicality must
be correlated with the evolution of cognitive capacities.Furthermore,
there is little question that the evolution of human cognitive capacities
and associated encephalization was primarily a correlate of the evolu-
tion of the capacity for language.
Let me review the problem of inferences from paleoneurology that
comes from the fossil record of hominid brains.The earliest of these,of
about three mya,were comparable with brains of living great apes in size
and presumably in the complexity of their operation.(Size and com-
plexity in brains are so intimately related that to distinguish them from
one another may be impossible.As a first approximation,every neuron
is connected to every other neuron in the mammalian brain,and because
they are packaged efficiently,the number of neurons as well as the com-
plexity of their interconnections are both estimated rather well by gross
brain size.) The brains of great apes and australopithecines are very
large,and we should not underestimate the cognitive capacities of our
ancestors who lived with them.We are learning from behavioral studies
of living great apes,including studies of their language capacities (Green-
field 1991),just how cognitively competent such animals can be.Whether
or not their “language”is homologous to human language,and perhaps
equivalent to an earlier stage of our linguistic evolution,remains an open
question.
To extend these speculations to the problem of musical expression,I
would contrast the acoustic dimension of human experience with its role
in the animal world generally.The most striking result in the neuro-
sciences on this issue is the discovery of the distinctive lateralization of
brain activity in professional musicians in contrast to even knowledge-
able amateurs,and its lateralization in both groups.The analogous
lateralization of birdsong is a charming analogue to this human
phenomenon,but it is obviously analogy rather than homology,to use194 Harry Jerison