"The reason for the need of long-chain omega-3 fatty acids in the human diet
may be evolutionary.  The primary reason for man's dominance on earth is his
brain.  The brain is the richest source of long-chain omega-3 fatty acids in
the body.  Since fishing didn't evolve until 20,000 years ago, how did man
obtain these relatively rare fats needed for brain development if he wasn't
eating fish?

The answer may be because (1) there were other sources of EPA besides fish,
and (2) he was a real weakling.

Compared to other predators a million years ago, man was a loser.  He was no
match for other animals who had superior strength and hunting skills.
However, man was a pretty good scavenger.  By the time he arrived at the
carcass, there wasn't much left.  Probably the one thing left were the bones
that the predators and stronger scavengers (like hyenas) just didn't have
the time to chew on or get their jaws around.  And the biggest bone was the
skull of the dead animal.

But man had one significant advantage, he had tools.  Tools (like stones)
that could break into the skull of the dead animal and access the brain,
which was very rich in long-chain omega-3 fatty acids.  Here was a classic
case of you are what you eat.  By eating scavenged brains rich in long-chain
omega-3 essential fatty acids, man stumbled upon the molecular building
blocks for more rapid development of his brain.  With more brain power, he
could make better tools and develop better hunting strategies.  By the
neo-Paleolithic era, about 10,000 years ago, man had become the most deadly
hunter on the face of the earth.  Now neo-Paleolithic man could eat whatever
part of the carcass he wanted, including the protein-rich muscle.

The meat from wild game contains nearly six times more long-chain omega-3
fatty acids than today's grain-fed beef.  So whatever neo-Paleolithic man
ate (brains or meat), he was getting a lot of the long-chain omega-3 fatty
acids, such as EPA.  As I mentioned earlier, in the last 50 years there has
been a dramatic decrease in the amount of omega-3 fatty acids consumed by
Americans.  In fact, nearly 20% of the American population today have such
low levels of EPA, it is difficult to shut down the activity of the
delta-5-desaturase enzyme, which leads to an increased production of AA
[arachadonic acid] and the generation of larger amounts of "bad"
eicosanoids."

source: The Anti-Aging Zone, Sears, p 175 -176

Rob