As you may have noticed, there is still considerable discussion and
controversy in this area, and absolutes and dire predictions should
be avoided.
Many countries are now adopting EFA dietary standards.
The problem apparently derives from the complex interactions
(competitions) between types of FA and other nutrients.
Most studies that I have read seem to focus on 3 areas:
1 What might have been the amounts and ratios available in
pre-farming diets.
2 What effects various essential(?) FA have on the optimal
evelopment of embryos and young creatures.
3 What effects complete elimination of a FA may have on animals, and
certain performance criteria.

Clearly humans have had to adapt widely to survive seasonal and
geographic availability, and are quite good at it. Since it is
almost impossible to totally eliminate PUFA or a particular FA from
the diet, much of the work seems to have focused on association with
either optimal performance, or with specific disease conditions.
Good luck with your cartoon. :-)

MikeV
Note: These are personal impressions of a former engineer and
eminent non-expert. (who chooses to eat a wide variety especially of
EFA containing foods)

The "International Society for the Study of Fatty Acids and Lipids
(ISSFAL)" appears to be one of the more authoritative groups.
http://www.fatsoflife.com/article.asp?i=c&id=209
http://www.jlr.org/cgi/reprint/35/1/169.pdf

     ISSFAL 2004 Recommendations September 2004
     ISSFAL Recommendations for PUFA Intakes in Healthy Adults

At the biennial meeting of the International Society for the Study
of Fatty Acids and Lipids (ISSFAL), held in Brighton, U.K., June
27-July 1, 2004, the ISSFAL Board approved the recommendations of a
subcommittee charged with the task of providing "recommendations on
the intake of different polyunsaturated fatty acids (PUFAs) ..." The
ISSFAL recommendations target healthy adults. A summary of the
recommendations follows.

* An adequate intake of linoleic acid is 2 percent of energy. ISSFAL
noted that although linoleic acid has been recommended in human
diets for about 40 years, there are no well controlled studies that
definitively establish the minimum required intake of omega-6 PUFAs
in healthy adults.

* ISSFAL recognized that there may be a healthy upper limit to the
intake of linoleic acid. At present, data are insufficient to set a
precise value on such an upper limit. Most populations consume more
than the adequate amount of 2% energy from linoleic acid. Some data
indicate that intakes above adequacy are beneficial with regard to
reduced plasma cholesterol and low density lipoprotein cholesterol
levels. On the other hand, risks associated with high linoleic acid
consumption include reduced high density lipoprotein cholesterol
levels, increased risk of gallstone formation, predisposition to
lipid peroxidation, and reduced incorporation of omega-3 PUFAs. The
ISSFAL subcommittee did not reach consensus about a dietary
recommendation on this question.

* A healthy intake of alpha-linolenic acid is 0.7 percent of energy.
Recommendations for the consumption of alpha-linolenic acid, the
plant-based precursor of the long-chain omega-3 PUFAs (n-3
LC-PUFAs), vary from 1.35 g/day (0.68% energy) by the Institute of
Medicine in the U.S. to 2.2 g/day (1% energy) from a panel of
experts. Five different countries or authoritative bodies have
recommended 2.0 g/day or 1% energy. ISSFAL's examination of the
available literature suggested that a healthy intake of
alpha-linolenic acid is about 0.7% of energy.

* For cardiovascular health, a minimum intake of eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA) combined is 500 mg/day.
EPA and DHA are the main n-3 LC-PUFAS. This recommendation is based
on ISSFAL's review of major epidemiologic studies in the U.S. in
which estimates of the consumption of n-3 PUFAs in healthy adults
were available. Five of six studies reported statistically
significant inverse trends between risk of coronary heart disease
and consumption of EPA + DHA. The relative risk reduction between
the highest and lowest intake groups was 37%, an effect associated
with the consumption of 566 mg EPA + DHA per day.

Details of the ISSFAL recommendations with references are on the
ISSFAL web site.

International Society for the Study of Fatty Acids and Lipids.
Recommendations for the intake of polyunsaturated fatty acids in
healthy adults. 2004.