>>The LCA almost certainly had a salt appetite. We then
>>adapted to a particularly salty diet and acquired even
>>more of a taste for the stuff.

Salt appetite and salt hunger in the face of deficiency is something which evolves in animals which do not live on diets with a lot of salt. Animals which do live on such diets either never evolve such an appetite or they lose it.

>> Of course, if salt is part of your diet, then you aren't hungry for
>> salt. I suspect if you fed a tiger low salt Kibbles and Bits that it
>> would develop a powerful salt hunger. Feed a cow salt laced silage and
>> it wouldn't have a salt hunger.

You are misunderstanding what is involved in salt hunger and salt appetite. Mammals which normally intake an excess of salt do not, according to experimental evidence, possess the instinctive drive to take in salt. They either never developed this drive (or it was lost) because they didn't need it.

>> This 'salt appetite', business should indicate, if anything
>> that we are somehow used to more salt than we get via
>> vegetables and not non-marine ancestry. On the other hand
>> salt is given to cattle and sheep too, so maybe it has nothing
>> to do with anything.

You've put forward two possibilities there, and neither is correct. Animals which exhibit "salt appetite" are those for whom such a mechanism has had important survival value during their evolution. Marine animals, for instance, have never had a need to search for or crave salt -- quite the opposite. On the other hand, animals such as humans, sheep, rats, rabbits -- and indeed most all terrestrial non-carnivores (carnivores get plenty of salt from meat) -- have evolved in environments in which this salt appetite was a crucial need, and consequently they typically exhibit such an appetite.

We, OTOH, are adapted to live on a low-salt diet, although, as is common with mammals so adapted, we like salt and sometimes overdo it considerably given the opportunity.