---
Don Matesz <[log in to unmask]>
First of all, let me say that I did not come up with the list of reasons to doubt a
savannah origin of man..some came from Crawford and Marsh (Nutrition and Evolution) and
some from a student of physiology who posted tehm on another board.
Hank McBridge <[log in to unmask]> wrote:
>Just a couple comments:
>
>Don wrote:
>
>..... Human sweat glands makes sense only if man
>evolved in a water-rich environment--such as at the land-water interface."
>
>Horses sweat profusely too.
But zebras, savanah animals, don't...anyway the same point still applies, an animal that
sweats profusely is at a disadvantage in a dry hot climate such as the savannah...your
point only suggests that horses also originated in an area having an abundance of
water...if so then it would have increased the chances of man and horse becoming friends
as they are.
>
>"5. Humans are the only primates capable of producing tears, a
>characteristic that is found in marine birds, crocodiles, and sea snakes."
>
>Dogs, cats, cattle and horses (to name a few) all produce tears.
So what? The point is that the human is the only PRIMATE that produces tears. What
accounts for this similarity to sea animals?
>
>"7. Humans are the only land animal that is not an obligatory nose
>breather, due to the fact that the larynx is connected to both the mouth and
>the nose; this adaptation also makes speech possible."
>
>Haven't you ever seen a dog pant?
Yes I have, please don't patronize me. As I said, part of the list came from another
source and when I read the list the fact that dogs pant didn't occur to me. However one
might argue that dogs also originated at the land water interface and that man and dog,
being so similar, became friends in that environment.
>
>"8. ...Human infants can swim spontaneously, with no instruction, at birth
>(and before six months of age)."
>
>Most puppies can swim also.
See my comments above. The fact that dogs can swim at an early age in no way discounts
the idea that man originated at the land water interface, it only supports the idea that
dogs originated in an environment where swimming was necessary and advantageous, such as
the areas where land and water meet.
>
>"S.B. Feldman" <[log in to unmask]> wrote:
>
><< No, land herbivores' brains do not have "all" the DHA required. Land
>herbi=
> vores have
> rather small
> brains which naturally contain only small amounts of DHA. For example a hi=
> ppo's brain is
> only .59 kg, an ox brain is only .45 kg, gorilla .40 kg, chimpanzee only .=
> 34 kg.
> Compared to man, 1.5 kg and dophin 1.6 kg. One man's brain is 3 times the =
> size of a
> gorilla's, and nearly 5 times the size of a chimpanzee's, over twice the si=
> ze of a hippo's
> brain. The remarkable thing is the close absolute and relative size of hum=
> an and dolphin
> brains. The human brain is 2 per cent of body weight, the dophin is 1 pe=
> rcent.
> >>
>Why don't you give the percent of weight for the first part of the paragraph
>as is done in the final section? It sounds like you are arguing something
>about a fixed amount of DHA being distributed in different size brains.
That's because in the first part of the paragraph I was addressing the quantity of DHA
available. According to Crawford and Marsh "A study of 42 species of mammals....showed
that although different fatty acids were used for muscles and livers, all species used the
idential profile of fatty acids in their brains. This held true depsite wide differences
in the fatty acids in food (dolphins or cows) or other parts of their bodies." Thus,
according to Crawford and Marsh, the percent DHA in brain tissue is fixed across species.
Therefore, small brains (small by mass) have only small amounts (i.e. few grams) of
DHA--and clearly many large land animals have quite small brains. As for the relative
brain sizes, hippo brain is .042% of body weight, ox brain .09%, gorilla brain .24%, and
chimp .55%. Thus on a 'relative to body weight' basis human brain size is 47 times that
of hippo, 22 times ox, 8 times gorilla, 3.6 times chimp.
>
Don
|
