>> Glenn cites Dean Falk as writing:
>> "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 recordi."
>> Some comments:
>> 1) Falk says "statistically associated with handedness in humans."
>> This is jargon for, "most times its associated with handedness, but
>> sometimes not". If these functions are so variable that we cannot
>> even say for certain that modern humans will have them in the same
>> place, how can we even begin to speculate about species that are
>> known only from bone scraps hundreds of thousands of years old?
Speculating is dead easy, and fine in it's place. I think it's a
reasonable assumption that H. habilis was more "humanlike" than any
living apes, with at least some rudimentary language, based on Broca's
region, the assymetries in fossil endocasts, and the evidence that the
makers of stone tools were predominantly right-handed. That's not proof
of anything, it's just informed speculation.
>> 2) "Have been detected on endocranial casts from the early part of
>> the hominid fossil record" sounds suspiciously guarded to me. How
>> certain is it that these patterns are impressions of a Broca's area
>> structure or homolog? Are there any dissenters in the evolutionary
>> community?
The two big names in fossil neurology, Ralph Holloway and Dean Falk,
disagree on many things but they agree on this, so it is probably widely
accepted.
>> Glenn writes:
>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?
>> So would I. How about it Jim?
I think that Glenn's post implied that monkeys have the assymetries of
human brains (to a lesser degree), but that's not a 'feature' that can
be removed. No-one has said that apes or monkeys have a Broca's region,
have they?
-- Jim Foley Symbios Logic, Fort Collins, COJim.Foley@symbios.com (303) 223-5100 x9765 I've got a plan so cunning you could put a tail on it and call it a weasel. -- Edmund Blackadder