I will trade you quotations. I have posted this before but here it is again.
"But monkeys don't have language and humans do. Are [141/142] there
morphological manifestations of human brains that (a) correlate with
functional lateralizations including language and (b) are capable of leaving
traces in the hominid fossil record? Indeed there are. Shape asymmetries of
the frontal and occipital lobes, known as petalias, exist in human brains
(and to a lesser degree in brains of monkeys and apes) and are statistically
associated with handedness in humans. Further, a characteristic sulcal
pattern associated with Broca's speech area in left frontal lobes is present
in human but not in ape brains. Both humanlike petalis and the pattern of
sulci associated with Broca's area have been detected on endocranial casts
(endocasts) from the early part of the hominid fossil record.
"The oldest evidence for Broca's area to date is from KNM-ER 1470, a H.
habilis specimen from Kenya, dated at approximately two million years ago.
From that date forward, brain size 'took off,' i.e., increased
autocatalytically so that it nearly doubled in the genus Homo, reaching its
maximum in Neanderthals. If hominids weren't using and refining language I
would like to know what they were doing with their autocatalytically
increasing brains (getting ready to draw pictures somehow doesn't seem like
enough)."~Dean Falk, Comments, Current Anthropology, 30:2, April, 1989, p.
141-142.
Your citation stated,
>> More importantly, an homologous
area has been demonstrated in monkey brains, so the appearance of
these gyri and sulci in fossils does not indicate the appearance
of a totally new structure (p. 117)<<
I might point out that "homologous" does not mean that it is capable of
performing the same function. Unless you have a talking rhesus monkey or
something, I dare say we have experimental evidence that the "lesser" degree
of structure in the monkey does not control speech. My right arm is
homologous to the right wing of a bird, but that does not give me the ability
to say that birds can not fly. Homologous structures may or may not have the
same function. Obviously the "lesser" structure in the monkey brain, does
not have the ability to gives speech.
And we do know what happens to a person who has a stroke in Broca's area,
they can not control the muscles of the larnyx. I quote
"Although ignored at the time, Wigan's speculations received some measure of
support less than twenty years later when a French surgeon, Paul Broca,
examined the brain of a patient who had been paralyzed and left almost
speechless by a stroke affecting his left hemisphere. Baroca suggested that
the patient's language difficulties (aphasia) could be explained on the basis
of a softening of one area of the left hemisphere. When other investigators
subsequently demonstrated similar language difficulties in other patients
with softening in the same location in the left hemisphere, it seemed
reasonable to conclude that the left hemisphere possesses a language center.
"Further support fo this early scientific demonstration of hemispheric
specialization came ten years later when a German neurologist, Carl Wernicke,
discovered a second and rather different speech center. While 'Broca's area'
is responsible for the conversion of thoughts into smoothly articulated
sounds, the speech area of Carl Wernicke is more involved in the process of
cnveying meaning." Richard M. Restak, _The Brain, Warner Books, 1979, p. 188.
Thus there is multiple confirmation that Broca's area is involved in speech
in many different people. Now I have no doubt that there are other areas of
the brain which process speech, but as far as I know, no other area is in
charge of the muscles of the larnyx. Does anyone else have any information
on this?
I would also like to get Jim Foley's opinion on the "homologous" features of
the monkey's brain. What happens to the monkey if that part of the brain is
removed?
glenn