Amadeus Schmidt wrote:
> Humans _are_ dependant on vitamin C, however.
> If you talk about one-cellers loosing sysnthesis capabilities in 50
> generations on whatever, what would you imply on humans then?
As I said, it may take longer, even much longer, but in any case it is
IRRELEVANT how long it takes. An inability to produce a nutrient in the
body (e.g. vitamin C) can develop over some (who cares how long) period
of time. Once that happens the species MAY not die out if said nutrient
becomes scarce (note I said scarce, NOT absent completely) if the specie
has strong advantages. This very well may have happened to humans.

> So, still all of our anchestors had a sufficient supply, _after_ the
> vitamin-c dependency developed.
Sufficient is not the same as plentiful, especially once you count the
special adaptations humans have to deal with the inability to produce
vitamin C. You were making two points - that vitamin C must have ALWAYS
been plentiful simply because it is a vitamin and without it we would die.
(The second was the fruits must have been a major part of our diets.)
I am arguing that it may very well have been plentiful a long time ago
(when we lost our ability to make it). Since then it didn't have to be
plentiful, merely sufficient to survive, and even then with special
adaptations.

> Would you propose that the vitamin-c dependency build up only recently?
> I would not consider that as probable because vitamin-c supplies tended
> to decline recently and not vice versa.
I fail to see anything I have said that would suggest that vitamin C
dependency developed only recently.

> It might be possible, that humans-anchestors
> did vitamin-C-synthesis
> for millions of years, and lost it
> if a period of warming, as you tell.
What period of warming? (As I tell? What did I say that could possibly be
intrepreted as this?)

> *If* they went through a bottleneck of few individuums, and if loosing
> the synthesis capability would have resulted in a strong
> evolutionary _advantage_.
> But I'd call it highly unlikely that such an event would have happened
> on a whole population of humans spread all over the world.
What does this have to do with anything I was talking about? I was trying
to point out that you can't assume that vitamin C must have ALWAYS been
plentiful in our food supply simply because we are dependent on it.
Why we evolved to have this dependency does not change the fact that we are.
If we developed it a long time ago and since then vitamin C became scarce in
(not absent from) our diets humans would not necessarily die out. This
basically defeats your argument. Your argument is like saying that because
desert animals are dependent on water it must have always been plentifull
in their environment. At one point long ago this was true. Since then
water became scarce, but they survived by developing adaptations.

> >Thus a diet high
> >in fruit is absolutely NOT required.
> Of course not, only probable.
If we can get sufficient C from diet totally devoid of fruit, then what
warrants the statement the diet high in them would be more probable?

> I read that there is no hunting animal in the world without the
> capability of vitamin-C synthesis.
> Even omnivores like rats can do it.
There are only two sets of mammals that can't synthesize vitamin C - primates
and guinea pigs. This makes for a very small sample size. Besides, what does
this have to do with what I was saying? (I am assuming that this message is
a reply to mine, if not - sorry).

Ilya