HUMAN BRAIN EXPANSION
In June 2000, NOHA Honorary Member Michael A. Crawford, PhD, gave an invited lecture in Japan at the 4th Congress of the International Society for the Study of Fatty Acids and Lipids on "Arachidonic and Docosahexaenoic Acids as Keys to Human Cerebral Expansion." Arachidonic acid is a 20-carbon chain, omega-6 fatty acid with four unsaturated positions and docosahexaenoic acid is a 22-carbon chain omega-3 fatty acid with six unsaturated positions. As we know, both omega-3 and omega-6 fatty acids are essential. We must obtain them from our food and we cannot convert an omega-3 fatty acid to omega-6 or visa versa.
Professor Crawford is a world authority on nutrition and most especially on the essential functions of certain fatty acids for brain development and function. He has led research showing that, with the exception of the brain, both the carbon-chain lengths and the proportion of omega-3 to omega-6 fatty acids can vary in different bodily tissues and in different species. However, the long-chain, highly unsaturated, essential fatty acids----arachidonic and docosahexaenoic are so predominant in the brains of all mammals that Professor Crawford has named them the "neural fatty acids" and the proportion of all the omega-3 to the omega-6 fatty acids is one-to-one in the brain. This situation is in striking contrast to most marine animals, for example, codfish muscle has a proportion of omega-3 to omega-6 of 40:1, in other words, overwhelmingly omega-3; whereas, most land mammals have the opposite lack of a one-to-one ratio, in other words, about three to six times more omega-6 than omega-3 fatty acids in their organs other than the brain. Professor Crawford points out that the mammalian placenta particularly concentrates the neural fatty acids for the brain of the fetus. However, if the diet is deficient, the brain will have to be small.
In The Driving Force: Food, Evolution, and the Future, Professor Crawford and his co-author make an excellent case for the development of our ancient ancestors on the seashore, where they could eat a fine combination of the long-chain neural fatty acids, in other words, both the omega-3s (exceedingly deficient on the savannah) and the omega-6s, as well as a great abundance of other essential nutrients. (See NOHA NEWS, Fall 1991, "Food: The Driving Force of Evolution.") On the seashore, as our bodies grew larger, our brains could have the nutrients to expand also and thus become far larger than the brains of our closest genetic relatives, the great apes. They developed in the forests far from the sources of omega-3, neural fatty acids. Thus, the great apes did not have an adequate source for the essential one-to-one balance of omega-3 to omega-6 fatty acids, necessary for brain development. Consequently, their brains remained relatively very small.
On May 4, 2000, an article and commentary appeared in Nature, giving evidence of our tool-making ancestors living on the coast of the Red Sea 125,000 years ago in Paleolithic times. Fortunately, the area studied was an emerged reef terrace and not hidden under water or destroyed by pounding waves. We can imagine our ancient ancestors living and developing near water and then as the commentator put it: "Coasting out of Africa" to beautiful, seaside areas, rich in nutrients, all over the world.
Crawford, Michael A. and David Marsh, The Driving Force: Food, Evolution, and The Future, Harper & Row, 1989
Walter, Robert C. et al, "Early human occupation of the Red Sea coast of Eritrea during the last interglacial, Nature, 405: 65-9, May 4, 2000.
Stringer, Chris, "Coasting out of Africa," Nature, 405: 24-7, May 4, 2000.
Article from NOHA NEWS, Vol. XXVI, No. 1, Winter 2001, page 1.