We are REALLY making some progress here!  May I summarize the progress to
date?  I hope my summary does not distort the positions of the
participants.

ASSUMPTION.  We are working from the same basic assumption and this helps
the discussion progress.  Our assumption is that we are seeking the Paleo
model.  We are not looking for a fat loss diet, a body-builder's diet, a
vegetarian alternative; we are not being influenced by the availability of
food in our local supermarket or being swayed by squeamishness, personal
dietary preferences or specific therapeutic needs.  So often discussion on
this list is inconclusive because the participants start from quite
different assumptions.

POINTS MADE

I posted <Pleistocene benchmarks for beef> on 6 October and proposed a
typology of sources of dietary fats to help get our assumptions consistent.

Richard (12 October) has sided with Prof Cordain:

** pasture fed and grain fed steers have vastly different fat profiles

** it is this difference that leads Cordain to advocate a <low fat> diet
when using 21st century meat to recreate a paleolithic diet

My 6 October post asked if the fat profiles are significantly different
between

** pasture fed steers and pasture fed uncastrated bulls

** farmed pasture fed cattle and wild, range roaming cattle, the former
undertaking an unnaturally small amount of exercise and undergoing very
little environmental stress compared with the latter which migrated
extensively and experienced droughts

** I also asked if we are comparing like with like when we compare Bos
taurus with <typical game meat>

Andrew (12 October) pointed out

** the paleolithic diet would contain organ fat and subcutaneous fat [and,
I add, marrow fat] as well as intramuscular fat

** organ fat is highly saturated [I ask: it its degree of satuation
significantly different across my four categories of sources?]

** the omega 6 : omega 3 ratio of fats in paleolithic meats can be ignored
for all practical purposes today on the assumption that 21st century meat
has fewer omega 3s and we should, therefore, supplement our meat with oily
fish or fish oils, but not flax oil

Liz (12 October) adds the following

** the protein : fat ratio in meat, when that meat is a dietary staple, is
significant.  It is significant because a human eating primarily low fat
meats (1) is not mimicking the diet of Pleistocene Homos who ate mainly
large, high fat animals ... until they wiped them out and had to resort to
low fat small game (2) [because it is inconsistent with human evolution]
when we get more than 40 per cent of our calories [per meal? daily?
weekly?] from protein, we suffer <rabbit starvation>.

** our bodies store as saturated fat the excess carbs we consume.  There
would be no evolutionary advantage in storing for later use saturated fat
if saturated fat was not harmless [at least] or beneficial [more likely]

Alex (also 12 October) sides with Richard

** Alex assumes that because 21st century grass fed beef is lean it allows
us to mimic adequately the meats Homos used as their staple during the
Pleistocene.  Alex also refers to a <cow> which may not be the same,
ceteris paribus, as a <steer> or a <bull>

There is still some way to go in this debate and I hope the above summary
is an effective invitation to more participants.  I'll prepare a new
summary if we make significant further progress.  Thanks to everyone so
far - a good example of what makes this list so valuable!

Keith