On Thu, 6 Apr 2000 16:45:15 +0200, Hans Kylberg <[log in to unmask]> wrote:

>At 06:37 2000-04-06 -0500, Amadeus wrote:
>
>>But this can result in a lasting change *only* if for a long time
>>the ascorbate supply from food is constantely high.
>>Because you need the time that all other individuals of the species
>>need the time to die off.

Hans:
>But if this happens during a population bottleneck, when food is scarce,
>but still contain vitamin C, this need not be for very long.

Ok, then you have to assume a population bottleneck, let say a group of
a few thousand, and exactely in this small group should occur exactely
at this time the mutation to loose vitamin C synthetisation.
This is unlikely.
Genetic mutations occur at random... many kill or deteriorate.

Such population bottlenecks made it probable to spread genes of a few
individuals over very many descendents.
But such a bottleneck means, that *all other* individuums have died off
or will die off. How can it be? What would kill all humans/hominids
except one small group in *all* africa, on whole earth?

Hm astonishing is , that this is similar, to what actually happened several
times. The population of homo erectus was completely replaced by
neanderthals (except maybe small parallel branches).
And the neanderthal population broke down and was completely replaced by us.
Maybe neanderthals *had* the ability to synthetize vitamin C? And this
is why they did so good as mammouth hunters in the winter?

But - i don't think this speculation is on a right path.
There are non-hominid primates which can't make ascorbate. So, a common
mutation should be searched far far back.
And the driving force, which let one type of hominid replace previous
branches can't be explained by additional energy possibly gained by *not*
making ascorbate, i think.

Still my explanation is as follows (this is not darwinistic ;-)):
An mammal population evolved in the wood amoung fruit.
Especially evolved the ability of climbing them, to better reach the fruit.
Animals can't make all molekules on their own, plants can.
Animals make new own molekules of others readily found in plants.
They only make molekules not found in the food. For example they don't make
amino-acids which are found in every food - the essentials.
They don't need to make ascorbate, if it's comeing reliably from food.
Fruit are a reliable source of ascorbate.
The ascorbate making regulative was turned off
all day, all year, all life. Unused abilities (also in metabolism)
die off in course of generations. Whales haven't fingers anymore.
Primates stopped using vitamin c synthetisation for generations for eons.
The unused genes could mutate or not in the eons without disadvantage for
the individuum. Gene copying has a fault rate. Undiscovered copy-faults
persist. Unused abilities disappear.


We know, that primates lived for many millions of years fruit-eating
in the woods.
Do we need annother "cause"?

regards
Amadeus
(I changed the thread header because I think the old one no longer
matches the discussion too good to identify some content)