>I interpreted this to mean that a wild animal eats a diet that is
>optimal for having the greatest number of offspring during its prime
>reproductive years, which is not necessarily a diet that is optimal
>for longevity, since evolutionary pressure is concerned much less with
>how long an individual lives and far more with how many individuals
>there are. A very high fat diet, to make up a random example, might be
>very nourishing during the reproductive years and cause heart attacks
>as an animal ages--that diet won't be selected against, because the
>offspring have already been produced before the end effect of that
>diet is felt by the individual, and thus there is no pressure to move
>away from that diet.

Yes. Pretty much. The ancestors found a useful niche and the niche and
needs to succeed reproductively applied pressures that resulted in
changes to morphology as those best suited to succeed reproductively
in those conditions had more mates or more offspring than the ones who
were as well suited. With many in Carnivora there has been a narrowing
on that regard. It might actually work against them. When there was a
careful (but invertebrate) follow-up study to the caloric deprivation
studies (most also on invertebrates) that indicated that longer
longevity accompanied reduced food intake the follow up study found
that not all calories are equal. It was protein restriction which
turned out to have the most benefit for the study subjects. If that
turns out to also hold for vertebrates it may be that a carnivorous
diet creates a Catch 22.

Unless members of older generations help increase the survival of their
progeny's children there is no selective reason to favor longevity. In
fact, older animals who are not reproducing are sometimes competition
with the younger ones for limited resources.

So, assumptions can't be made about what is best for longevity, not
even in diet. Older ferrets might turn out to need less protein, or
lowered sources of phosphorous, or more omega 3 fatty acids, for
instance, to keep aging kidneys in their best shape. Other organs
have their own needs as time goes on, too.

BTW, in humans there are even studies indicating that we humans CRAVE
high fats and salts partly because in the wild they are harder to get
so the urge got built in for survival's sake.

Sukie (not a vet)
Reminder:  THE FERRET HEALTH LIST IS MOVING.
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Recommended ferret health links:
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http://ferrethealth.org/archive/
http://www.afip.org/ferrets/index.html
http://www.miamiferret.org/fhc/
http://www.ferretcongress.org/

[Posted in FML 5428]