Thanks to Melissa Darby and Barry Groves for raising some interesting
points in their replies. I am curious as to whether Sagittaria latifolia is
easily digested without cooking and what sort of calorie returns are
available.  If it is not possible to provide enough fat from temperate and
tropical animals without resorting to carbs then perhaps we should be
looking for similar plants to S. latifolia around the world that could have
provided these carbs.

In response to Barry Groves his comments about the fat in the brain are
probably valid in that use of the brain and marrow would have increased the
fat availability.  I don't remember if Gould (1966) included fat from the
brain in his estimate. I suspect not. In Gould (1980:193) he mentions
people of the Western Desert "breaking up or pounding carcasses in order to
obtain every last scrap of edible material" so they were probably getting
at the bone marrow as well.  However, many years ago I brain tanned a
Kangaroo skin using Kangaroo brain and I vaguely remember that the brain
was not very large (smaller than a closed fist). The energy return from fat
is around 38kJ/g, and carbohydrate and protein both return around 17kJ/g.
Even with double the energy return from fat I'm not convinced that there is
enough fat on these animals to compensate for the protein quantity.
Perhaps someone has figures on total fat contents from animals (including
brain and marrow).  As Barry points out they ate other fat resources e.g.
insects.

However, it appears that all Aboriginal groups that I have investigated had
a carbohydrate staple.  This could simply reflect the fact that animal
resources were becoming scarcer in more recent times.  Although, if one
believes that early people were mainly exploiting large animals with
sufficient fat and the absence or low levels of carbohydrate then perhaps
gluconeogenesis was the norm for earlier people.  It seems more likely to
me that they were exploiting some form of carbohydrate such as the
S.latifolia as suggested by Melissa

Cheers

Sean McBride

Gould, R.A.
1966    Notes on hunting, butchering and sharing among the Ngatatjara and
their neighbours in the Western Australian desert. Kroeber Anthropological
Society Papers 36:41-63.

Gould, R.A.
1980    Living Archaeology. Cambridge University Press, Cambridge.
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