Esperanza,
So you want to be a food anthropologist, uhh? That must be an
interesting field! Did you know that tamalli is Nahuatl for tamal?
You're right about the pork tamales, pork (and lard) became an
available filling until after the Spanish colonization. But before
that, tamales came in a much wider variety that what we can now
imagine, for example, tamales were made of fish, tadpoles, bees,
honey, seeds, frogs, ants, tomato, corn, sweets, anything that was
available at the time.
According to some, the original recipe of this millenary dish came
out of the need to create a portable food, one that warriors could
easily take with them to the battle fields, etc. The tamal wrap was
ideal as it protected and preserved the food from contamination, etc.
There is plenty of information available online if you do a search
for a combination of keywords, like tamalli, tamal, nahuatl, masa,
etc.
Now, speaking about the indigenous (Amerindian) diet versus what
experts say is