Taung: A Fossil to Rival Piltdown - The Fossil Chronicles - page 23

even separated by little sulci, which reflects the extraordinary degree
to which these animals use their forepaws to explore the environment . 16
Similarly, those monkeys from the New World that have grasping and
highly manipulative tails have tail representations that are so expanded
that they sometimes form extra convolutions, 17 a feature that has been
observed on their endocasts as well as their brains . 18 Another function-
ally significant modification that appears on some monkey endocasts is
the extraordinary hook-shaped sulcus in gelada baboons that seems to
be related to enlarged face representations that facilitate this species'
amazing ability to flip its upper lip over its nose. 19
Humans, of course, do not have prehensile tails or engage in making
faces that entail lip-flips. We do, however, use our hands extensively,
which is reflected in the relatively large size of the little homunculus's
hands in figure 2. We have also evolved highly rich symbolic language,
which sets us apart from all other animals. Interestingly, language func-
tions are represented mostly on the left side of the human brain, and the
“speaking” area labeled in figure 2 (known as Broca's speech area) has
a distinctive arrangement of sulci that is unique to humans. Although
language origins is a highly controversial subject, analyses of hominin
endocasts have led scientists who study brain evolution (paleoneurolo-
gists) to conclude that the convolutions associated with Broca's speech
area began to evolve a very long time ago. 20
Nevertheless, endocasts of primates vary enormously in the amount
of anatomical detail they reproduce. Sometimes they reveal little, if
anything, about the brain's all-important convolutions and the sulcal
grooves that separate them—especially in bigger-brained species such
as Homo sapiens. Although endocasts of smaller-brained species, like the
one that Dart discovered, are likely to show more detail, the amount
of information they provide is still subject to a good deal of variation.
There is, thus, a huge element of luck involved in studying hominin
endocasts. When it comes to studying the cerebral cortex, endocasts
simply are not as revealing as actual brains. In the fossil record, how-
ever, endocasts are all that we've got (at least, until the time machine is