Short reply:
It seems that the figure posted for protein intake of this aboriginal group
(80% of dietary energy coming from protein) is an overestimate.

Long reply:
After viewing the abstract (originally mentioned by Todd Moody) regarding
protein intake, it appears that concerns over the macronutrient profile
being incompatible with human metabolism seem premature.  The abstract-
(copy & paste the following):

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?
cmd=Retrieve&db=PubMed&list_uids=6373464&dopt=Abstract

-mentions that 64% of the total energy intake was provided by "animal food"
(which itself may be up to 80% protein and 20% fat), bu
t this leaves 36% of
the energy in the diet provided by plant foods, which would bring the
relative contribution of energy from protein down, perhaps to a level that
is metabolically manageable (but still high at around 60%!).

Another confounder, however, is the reported value for total energy intake,
which was only 1200 kcal/person/day.  At 1200 kcal and 60% protein, only
180 grams (720 kcal) of protein would be consumed, which is well within
estimates (for a mean body wt of about 80 kg, reported by O'Dea) of the
physiologic protein ceiling which has been worked out by Cordain et al (Am
J Clin Nutr 2000 Mar;71(3):682-92) to be around 3+ g/kg bdy wt).

Ed Thompson