Page 22 - Research 1.0

social networks, and in humans, where the development of
language enabled a culture built around tool manufacture and
use. Cooperative hunting no doubt played a role as well. The
challenges of a rapidly changing climate may also have been

a contributing factor. If it had not been for the development
of language, humanity would have had to continuously re-
invent the Acheulian Hand Axe. Two factors allowing human
speech are the hyoid bone, also present in Neanderthals, to
which the muscles of the tongue are attached, and a particular
variant of the FOXP2 gene found in other mammals that allows
for complex speech. Humans share this variant with both
Neanderthal and Denisovans, indicating that it was inherited
from a common ancestor. Neither chimps, bonobos or other apes

have that variation, indicating that it arose sometime after
the species diverged.

So, yes, the human evolutionary history is indeed complex,

but as Richard Feynman said, "Science is the joy of finding
things out.". We are getting a lot of clues as to the
expansion of the human brain from embryology and comparative
genomics, but we see a progression in brain size from early
mammals to primates, to monkeys, to apes and to humans. In
addition, while most mammal brains are smooth, primate brains
have convolutions which increase the surface area of the
cortex. Those convolutions increase from monkeys to apes and
more in humans.

See: "Molecular evolution of FOXP2, a gene involved in speech
and language". Wolfgang Enard, Molly Przeworski, Simon E.

Fisher, Cecilia S. L. Lai, Victor Wiebe, Takashi Kitano,
Anthony P. Monaco, Svante Pääbo Nature 418, 869 - 872 (22 Aug
2002)

http://www.nature.com/nature/journal/v418/n6900/full/nature
01025.html