Did Algae Make Us Human?
by Mark Edwards
Algae saved our planet 3.5 billion years ago by transforming the hot and deadly CO2 and methane atmosphere to enough oxygen to support life. Only 2 million years ago, algae may have performed another incredible feat by providing the micronutrients that triggered human brain enlargement. Brains that expanded three times larger than chimpanzees, differentiated our Homo ancestors from their pre-human and primate cousins.
A mystery nutrient source triggered brain enlargement, encephalation, around 2 million years ago. Scientists agree that early hominoids had to find a more energetic diet richer than their prior primate diet of nuts, leaves, bark, shoots, roots and insects. The new diet needed to be rich in vital nutrients, especially protein and omega-3s to support brain enlargement. Textbooks suggest that early Homo took a one step path to encephalation by expanding their diet to include savanna game meat, which would have provided the energy and nutrients necessary to develop and support larger brains.
However, meat acquisition would have required small brained (slightly larger than chimp brains) and scrawny early hominoids to compete with wild animals to acquire meat. Early Homo sacrificed muscle mass, size and speed for walking upright and a slight increase in brain size. The game meat scenario ignores the substantial energy and survival risk associated with competing with much bigger, faster and stronger wild animals with specialized scavenger and hunting skills. African predators 2 million years ago were twice the size they are today.
The human brain enlarged a million years before hunting weapons or cooking fires were invented. Had early Homo hunted meat without weapons, they would have most likely become the food chain. Even had they found meat, they lacked the teeth to tear off or masticate raw meat. Their stomachs could not digest raw meat, which probably would have given them raging diarrhea. A nutritious, safe, convenient and digestible food source rich in omega-3s must have preceded game meat consumption to permit the initial stages of brain enlargement.
Omega-3 fatty acids
DHA comprises 27% of the polyunsaturated fat, and 97% of the omega-3 fatty acids in the brain. Arachidonic acid (ARA), an omega-6 long-chain polyunsaturated fat, comprises 35% of the polyunsaturated fat, and 48% of the omega-6 fatty acids in the brain. Together DHA and ARA account for nearly two-thirds of the structural fat in the brain. They are essential for normal brain development and function as well for operations of the eyes and heart. These fatty acids are concentrated in the region of the brain responsible for complex thinking skills — critical for food acquisition.
Mammals have a limited capacity to synthesize DHA and ARA from dietary precursors, so fatty acids were likely the limiting nutrients that constrained the evolution of larger brain size in most mammalian lineages. Wild plant foods available on the African savanna, grasses, grains, tubers and nuts contain negligible ARA and DHA. Muscle tissue and organs of wild African ruminants would have provided only moderate levels of these key fatty acids.
Down the food chain
Rather than moving up the food chain to game meat, early hominoids’ first step may instead have been down the food chain when they ingested algae in their drinking water. Consuming algae may have been intentional but more likely was incidental because the tiny algal cells were visible only in the sense that they turned the water slightly green. The lakes and wetlands in the Rift Valley where humans developed larger brains are home to some of the oldest lakes and wetlands on Earth that produce plentiful natural stands of the high protein and nutrient rich spirulina algae. Spirulina is the best selling algal nutritive supplement on the market today because it provides a complete set of essential nutrients. A hominoid tribe on the lee side of an algae lake may have ingested several grams of algae daily in their drinking water. These few grams of algae would not have provided sufficient roughage or protein for a full diet. Algae would have acted as a natural food supplement to supply the essential nutrients, vitamins and antioxidants that provided the green spark for encephalation.
Early Homo may have been attracted to the green sweet water because their bland, dry and gritty diet was nearly devoid of sweetness. Algae attract a wide variety of other nutritious microorganisms including yeasts, fungi, bacteria, viruses and other microorganisms that would have provided additional nutrient value. When ingested, algae create a feeling of satiation from moderated glucose release, which would have been a godsend for mothers with hungry infants. Algae also facilitate digestion so mothers may have made sure their offspring drank green sweet water loaded with algae after meals. On the lee side of lakes and wetlands, the wind blows algae into mats that could have been harvested easily with a sweep of the hand. These concentrated algae may have been attractive for its sweet taste as well as protein value.
As their brains enlarged, early Homo may have expanded their diet by exploiting the aquatic ecosystem for algal feeders loaded with algal protein and nutrients such as invertebrates, shell and fin fish, insects and amphibians. Algal nutrients were available locally, year round and were easy to harvest and ready to eat or to dry and store for later consumption. Algae may have served as the original tasty convenience food and provided healthy protein with a full set of critical amino acids, essential fatty acids that supported brain and body development as well as critical vitamins and minerals. Indigenous populations in Africa continue to harvest algae from mats floating on the water to use as nutritional supplements.
Early human brains were not the only body part that benefited from algae. Today the four most prevalent deficiency diseases globally in public health are: malnutrition, nutritional anemia (iron and B12 deficiency), xerophthalmia (vitamin A deficiency) and endemic goiter (iodine deficiency). Each of these nutrient deficiencies would have challenged pre-humans that had neither hunting weapons nor hunting skills and also lacked cooking fires. Forest and savanna plant foods, especially in winter and spring, would have imposed severe nutrient deficiencies on early hominoids. Without cooking fires to soften cell walls and release nutrients in foods such as nuts, grains, shoots and roots, much of the nutrient value would have been lost to early Homo.
It may seem improbable that a tiny algal supplement can provide sufficient vitamin A, iodine, iron, zinc and other nutrients even when the local diet does not. Typically, these critical trace elements exist in the local water but in extremely weak dilution. People, especially children, are unable to drink enough water to acquire sufficient iodine. In many ecosystems, little fresh water is available for drinking. Algae’s secret to high nutrient value stems from its ability to bioaccumulate nutrients in water at 1,000 times ambient levels. This means that even when some nutrients, minerals or vitamins may be lacking in human diets, algae can concentrate those nutrients in the green biomass.
Once hominoid brains and bodies reached critical mass, Homo sapiens expanded their diets and eventually became hunters. The first fossil record of a hunting weapon is only 400,000 years old. The addition of hunting weapons and cooking fires then enabled a more diverse diet and the development of modern human brains, communication and cooperation.
The dietary path to becoming human may not have been one step up the food chain to harvest savanna game meat. More likely, our ancestors first waltzed two steps down the aquatic food chain for the nutritional benefits of algae, especially the omega-3s. After their brains had enlarged thanks to algae nutrients, our ancestors were prepared to take the big step up the terrestrial trophic food web to harvest game meat.