that perceptual-cognitive functions of neocortex evolved progressively
in at least some lineages.
Complementing this information,we know from the analysis of brain
size in many living species of mammals that diversification with respect
to relative size included the evolution of species that remain at essen-
tially the same level of encephalization as the earliest mammals of which
we have records.Living Virginia opossums (Didelphis marsupialis) and
living European hedgehogs (Erinaceus europaeus) are quite comparable
with the earliest mammals in which brains are known in this regard.This
is evidence,of course,that mammals do not live by brains alone,and that
today in many niches an essentially minimal brain size is sufficient to
control all necessary behavioral functions.
With respect to musicality,wherever we have evidence of mammalian
vocal expression that we would describe as musical,we must consider
that,from the perspective of the species,a variety of neural mechanisms
may be involved in their generation and experience,and these may have
little to do with music as a human dimension of experience.
The fossil record on the evolution of bird brains is limited.Informa-
tion on the brain of the oldest known fossil bird, Archaeopteryx
lithographica(Jerison 1973),adds little to our knowledge of the evolu-
tion of musicality in birds.With the exception of Archaeopteryx,fossil
birds had brains that appear to have been very much like those of living
species.Major structures in living birds known to be related to vocaliza-
tion,although relatively large (Arnold 1980),are not manifested in the
external appearance of the brain in a way that would be measurable on
an endocast.The brain of Archaeopteryxdiffered from that of all living
birds in lacking a Wulst,an expansion of dorsal forebrain that functions
analogously to visual neocortex in mammals.In overall size,however,it
was within the range of encephalization of living birds and more
encephalized than brains of its relatives among the dinosaurs.(This
evidence remains uncertain,since the brains of the closest dinosaur
relatives of Archaeopteryxare not yet known as endocasts.)
One cannot discuss brain functions in birds in ways exactly compara-
ble with those functions in mammals.One can make confident statements
about neocortex in mammals with respect to a role in cognitive and per-
ceptual activities,but neocortex is solely a mammalian structure.It may
be that hyperstriatum in birds functions as an organ homologous to
neocortex (Karten 1991),and evidence from studies of effects of brain
damage is consistent with a view that,like mammalian neocortex,the
bird’s hyperstriatum has perceptual-cognitive functions (Macphail 1993;
Divac 1994).
The place of birds as model animals for studies of musicality is deter-
mined by their use of elaborate songs for various behavioral controls,191 Paleoneurology and the Biology of Music