The Role of Docosahexaenoic and the Marine Food Web as Determinants of Evolution and Hominid Brain Development: The Challenge for Human Sustainability

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Prof. Michael Crawford, of the Institute of Brain Chemistry and Human Nutrition, United Kingdom, explains that fish and seafood provide docosahexaenoic acid (DHA), an Omega-3 fatty acid that the brain needs to function efficiently. Prof. Crawford warns that the general lack of DHA in the current human diet could lead to mental health problems. This underscores the urgency of efforts to manage the world’s fisheries and maintain a healthy supply of this food. Lipids (fats) played a major, as yet unrecognized, role as determinants in evolution. Life originated 3 billion years ago. For the first 2.5 billion years of life, there was ample opportunity for DNA modification. Yet during that time there is no evidence of significant change in life forms. It was not until about 600 million years ago when the oxygen tension rose to a point where air breathing life forms became thermodynamically possible, that a major change is abruptly seen in the fossil records. The sudden appearance of the 32 phyla in the Cambrian fossil record was also associated with the appearance of intracellular detail not seen in previous life forms. That detail was provided by cell membranes made with lipids (membrane fats) as structural essentials. The compartmentalization of intracellular, specialist function as in the nucleus, mitochondria, reticulo-endothelial system and plasma membrane led to cellular specialization and then speciation. Thus not just oxygen but also the marine lipids were drivers in the Cambrian explosion. Docosahexaenoic acid (all-cis-docosa-4,7,10,13,16,19-hexaenoic acid, C22:6ω3 or C22:6,n-3, DHA) is a major feature of marine lipids. It requires six oxygen atoms to insert the six double bonds so it would not have been abundant before oxidative metabolism became plentiful. Docosahexaenoic acid (DHA) provided the membrane backbone for the emergence of new photoreceptors that converted photons into electricity laying the foundation for the evolution of other signaling systems, the nervous system and the brain. Hence the omega 3 DHA from the marine food web must have played a critical role in the evolution of vision and the brain. There is also clear evidence from molecular biology that DHA is a determinant of neuronal migration, neurogenesis and the expression of several genes involved in brain growth and function. That same process was essential to the ultimate cerebral expansion in human evolution. There is now incontrovertible support of this hypothesis from fossil evidence of human evolution taking advantage of the marine food web. Lipids are still modifying the present evolutionary phase of our species with their contribution to a changing panorama of non-communicable diseases. The most worrying change in disease pattern is the sharp rise in brain disorders which in the European Union has overtaken the cost of all other burdens of ill health at €386 billion for the 25 member states at 2004 prices, and in the UK, £77 billion in 2007 and £105 billion in 2010, a cost greater than heart disease and cancer combined. The rise in mental ill health is now being globalized. The solution to the rising vascular disorders last century and now brain disorders lies in a radical re-appraisal of the food system which last century was focused on protein and calories with little attention to the requirements of the brain. The development of marine agriculture from estuarine, coastal and oceanic resources in a way that mankind learnt to develop land resources 10,000 years ago, is likely to play a key role in this re-appraisal and in our future health and intelligence.