"Leif Erikson" > wrote in message k.net...
> ant and dec wrote:
>
> > S. Maizlich wrote:
> >
> >> ant and dec wrote:
> >>
> >>> pearl wrote:
<..>
> >>>> Proc Biol Sci. 1998 Oct 22;265(1409):1933-7.
> >>>> Visual specialization and brain evolution in primates.
> >>>> Barton RA.
> >>>> Department of Anthropology, University of Durham, UK.
> >>>>
> >>>> Several theories have been proposed to explain the evolution of
> >>>> species differences in brain size, but no consensus has emerged.
> >>>> One unresolved question is whether brain size differences are a
> >>>> result of neural specializations or of biological constraints
> >>>> affecting the whole brain. Here I show that, among primates,
> >>>> brain size variation is associated with visual specialization.
> >>>> Primates with large brains for their body size have relatively
> >>>> expanded visual brain areas, including the primary visual cortex
> >>>> and lateral geniculate nucleus. Within the visual system, it is, in
> >>>> particular, one functionally specialized pathway upon which
> >>>> selection has acted: evolutionary changes in the number of
> >>>> neurons in parvocellular, but not magnocellular, layers of the
> >>>> lateral geniculate nucleus are correlated with changes in both
> >>>> brain size and ecological variables (diet and social group size).
> >>>> Given the known functions of the parvocellular pathway, these
> >>>> results suggest that the relatively large brains of frugivorous
> >>>> species are products of selection on the ability to perceive
> >>>> and select fruits using specific visual cues such as colour.
> >>>> The separate correlation between group size and visual brain
> >>>> evolution, on the other hand, may indicate the visual basis of
> >>>> social information processing in the primate brain.
> >>>>
> >>>> PMID: 9821360 [PubMed - indexed for MEDLINE]
> >>>> http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract
> >>>
> >>> Thanks again.
My pleasure. Thanks for bringing it up. The "Christmas
Lecture" on Ch5 is frankly driving me up the wall. grrr.
> >>> I have moved my position on whether meat had a major part to play in
> >>> human evolution. I will read more, but on balance there seems little
> >>> evidence to support that it did.
Apart from helping humans survive times of scarcity, ..no.
'The historical role of meat in human diets has probably varied
significantly, as Jared Diamond, who is an authority on human
evolution, points out:
..... while early humans ate some meat, we do not know how
much meat they ate, nor whether they got the meat by hunting
or scavenging. It is not until much later, around 100,000 years
ago, that we have good evidence about human hunting skills,
and it is clear that humans then were still very ineffective
big-game hunters. Human hunters of 500,000 years ago and
earlier must have been more ineffective.
.....
Western male writers and anthropologists are not the only men
with an exaggerated view of hunting. In New Guinea I have lived
with real hunters, men who recently emerged from the stone age.
..... To listen to my New Guinea friends, you would think that
they eat fresh kangaroo for dinner every night and do little each
day except hunt. In fact, when pressed for details, most New
Guinea hunters admit that they have bagged only a few
kangaroos in their whole life.
The Rise and Fall of the Third Chimpazee, Jared Diamond, 1991,
pp.33-34
In The Origin of Humankind, Richard Leakey mentions Lewis
Binford, who suggested that systematic hunting of any kind
began to appear only when modern humans evolved, giving
dates of 45,000 to 38,000 years ago.
(We now know that modern humans were roaming
Africa at least around 195,000 years ago. / 'pearl')
What is obvious is that a mother and her infant cannot engage
in hunting, or any other arduous food gathering activity. Of all
the primate foods, fruits are the most easily gathered. They may
be obtained without the use of digging or cracking tools, climbing,
and digested with no need for hind-gut fermentation, such as is
the case with foliage. Most significantly, it is the feeding limitations
of the nursing mother which determine what foods she, and her
offspring will have continually available.
...
Given a plentiful supply of fruits the mother does not have to
risk expending much of her effort obtaining difficult to get foods
like raw animal flesh, insects, nuts and roots. Furthermore, fruits
contain abundant supplies of sugars which the brain solely uses
for energy. The mother who's genes better dispose her for an
easy life on fruits would have an advantage of those who do not,
and similarly, the fruit species which is the best food for mother
and child nutrition, would tend to be selected for. There is now
little doubt amongst distinguished biologists that fruit has been
the most significant dietary constituent in the evolution of humans.
....'
http://tinyurl.com/dahps
> >> It is UNDISPUTED by evolutionary biologists that meat played an
> >> indispensable role in human evolution. Meat's role was both direct and
> >> indirect. The direct role was in providing the massive amount of
> >> protein needed for brain development. The indirect role is as an
> >> organizing principle of human activity.
'What are the essential biochemical properties of human metabolism
which distinguish us from our non-human primate relatives? One, at
least, is our uniquely low protein requirement as described by Olav
T. Oftedal who says:
"Human milk has the lowest protein concentration (about 7% of energy)
of any primate milk that has been studied. In general, it appears that
primates produce small daily amounts of a relatively dilute milk (Oftedal
1984). Thus the protein and energy demands of lactation are probably
low for primates by comparison to the demands experienced by many
other mammals."
The nutritional consequences of foraging in primates:
the relationship of nutrient intakes to nutrient requirements, p.161
Philosophical Transactions: Biological Sciences vol 334, 159-295,
No. 1270
One might imagine that given our comparatively 'low protein' milk,
we would not be able to grow very fast. In fact, as the image on the
right shows, human infants show very rapid growth, especially of
the brain, during the first year of life. Human infants are born a full
year earlier than they would be projected to, based on comparisons
with other animals. This is because of the large size their brains reach.
A human infant grows at the rate of 9 kg/year at birth, falling to
3.5 kg/year a year later. Thereafter its growth rate is about half that
of a chimpanzees at 2 kg/year vs. about 4.5 kg/year. Humans are
relatively half as bulky as the other great apes, thus allowing nutrients
to be directed at brain development and the diet to be less demanding.
The advantages of such an undemanding metabolism are clear.
Humans delay their growth because they 'catch up' later, during
puberty as seen on the graph. Even so, the growth rate never reaches
that of a newborn infant who grows best by only eating breast milk.
....
According to Exequiel M. Patiņo and Juan T. Borda 'Primate milks
contain on the average 13% solids, of which 6.5% is lactose, 3.8%
lipids, 2.4% proteins, and 0.2% ash. Lactose is the largest component
of the solids, and protein is a lesser one'. They also say that 'milks of
humans and Old World monkeys have the highest percentages of
sugar (an average of 6.9%)' and when comparing human and non
human primate milks, they have similar proportions of solids, but
human milks has more sugar and fat whereas the non human primate
milks have much more protein. They continue 'In fact, human milk
has the lowest concentration of proteins (1.0%) of all the species
of primates.' Patiņo and Borda present their research in order to
allow other primatologists to construct artificial milks as a substitute
for the real thing for captive primates. It is to be expected that these
will have similar disasterous consequences as the feeding of artificial
bovine, and other false milks, has had on human infants.
Patiņo and Borda also present a table which compares primate milks.
This table is shown below and identifies the distinctive lower protein
requirements of humans. [see link]
Undoubtedly these gross metabolic differences between humans
and other mammals must have system wide implications for our
metabolism. They allow us to feed heavily on fruits, and may
restrict other species from choosing them. Never the less, many
nutritional authorities suggest that adult humans need nearly double
(12% of calorific value) their breast milk levels of protein, although
it is accepted that infant protein requirements for growth are triple
those of adults. The use of calorific values might also confuse the
issue since human milk is highly dilute (1% protein), and clearly
eating foods that might be 25 times this concentration, such as
meat, are massive excesses if constantly ingested. Certainly the
body might manage to deal with this excess without suffering
immediate problems, but this is not proof of any beneficial
adaptation. It also needs to be pointed out that berries, such as
raspberries, may yield up to 21% of their calorific value from
protein, but are not regarded as 'good sources' of protein by
nutritional authorites. There are millions of fruits available to
wild animals, and blanked generalisations about the qualities
of certain food groups, need to be examined carefully, due to
some misconceptions arising from the limited commercial fruits
which we experience in the domestic state.
The weaning of a fruigivorous primate would clearly demand
the supply of a food with nutritional characteristics similar to
those of the mothers milk. We must realise that supportive
breast feeding may continue for up to 9 or 10 years in some
'primitive' peoples, and this is more likely to be representative
of our evolutionary history than the 6 month limit often found
in modern cultures. This premature weaning should strike any
aware naturalist as being a disasterous activity, inflicting untold
damage. However, what we do know of the consequences is
that it reduces the IQ and disease resistance of the child, and
that the substitute of unnatural substances, like wheat and
dairy products, is pathogenic.
Finally we need to compare some food group compositions
with human milk in order to establish if any statistical similarity
exists. This would demonstrate that modern humans have
inherited their ancient fruigivourous metabolism. This data is
examined below in the final sections of the article.
.....'
http://tinyurl.com/dahps
> > I need to investigate more. The reference above seems to give a strong
> > case for a "visual specialization" evolution and it states that "no
> > consensus has emerged", but I'm happy learn and admit my ignorance on
> > brain evolution theories.
'There is a popular notion that anthropology can offer useful
insights for forming the basis of a dietary philosophy.
Anthropology is a science which is only just starting to mature,
previously having been little more that a systematic, but lose,
body of "say-so" information which attempted to explain our
species history and origins. With advances in dating methods,
including DNA analysis and more fossil finds, the science is
now embarking on its integration with biology. Previously,
anthropology was a pseudo-scientific marriage of traditional
views attempting to link the findings of robust sciences, such
as geology, palaeontology and archaeology. However, even
though anthropologists like Richard Leakey are aware that
their 'science' is often "based on unspoken assumptions"
(The Making of Mankind, p. 82, R. Leakey), they show that
they will persist in making them.
Anthropologies 'Man The Hunter' concept is still used as a
reason for justifying the consumption of animal flesh as food.
This has even extended as far as suggesting that animal foods
have enabled or caused human brain enlargement. Allegedly
this is because of the greater availability of certain kinds of fats
and the sharing behaviour associated with eating raw animal
food. The reality is that through natural selection, the
environmental factors our species have been exposed to
selected for greater brain development, long before raw animal
flesh became a significant part of our ancient ancestors diet.
The elephant has also developed a larger brain than the human
brain, on a diet primarily consisting of fermented foliage and
fruits. It is my hypothesis that it is eating fruits and perhaps
blossoms, that has, if anything, contributed the most in allowing
humans to develop relatively larger brains than other species.
The ability of humans to develop normal brains with a dietary
absence of animal products is also noted.
....'
http://tinyurl.com/dahps
> What is not in dispute is that the earliest hominids
> and their pre-hominid ancestors *all* naturally ate
> meat. To say then that meat played no role in their
> evolution is just factually wrong.
You cannot support your *claims* with evidence, ball.