by Mark Edwards
ossibly the most interesting unanswered question in science is: “How did we become human while our contemporary Homo cousins became extinct?” In a prior article, I proposed a new “down the food chain” theory that algae made us human but did not explain why our ancestors were motivated to an algae diet.
Our ancestor’s attraction for the sweet taste of algae may have played a significant role in our becoming human. Strategically placed evidence on our tongues provide fascinating clues that science has so far missed. Our pre-human ancestors made a significant, possibly accidental, decision to ingest algae, which may have led to the evolution our large brain and enabled Homo sapiens to evolve, thrive and rise to the top of the food chain.
Scientists agree that brain enlargement—encephalation—differentiates Homo sapiens from our ancestors. Our pre-human ancestors evolved from chimpanzees around 8 million years ago (mya) but very little happened to the brain for the first 6 million years. About 2 mya, brain enlargement began and by 1.5 mya, the humanoid brain was three times the size of chimpanzees. What happened to our ancestors during this half a million years of evolution? Humanoids survived their first million years with larger brains before cooking fires or hunting weapons were invented.
Larger brains require substantially more energy because brain mass consumes 16 times more energy than muscle mass. Therefore, our ancestors traded muscle for brains. Something triggered brain enlargement and the logical answer was a change in diet. Current theory posits that our ancestors moved from the primate diet of leaves, bark, insects and occasionally fruit to a more diverse diet, higher on the food chain that included game meat.
However, moving up the food chain to hunt game meat would have been problematic for slow, scrawny hominids that the fossil record shows had a stature of only 3.5 feet. Relative to predators, they had weak senses; including sight, hearing and smell. Had they decided to hunt, they would have entered the food chain rather than dominating other animals.
Other scientists suggest early hominids practiced scavenging to gather game meat. They may possibly have found bones that could be pounded for the marrow. Since both predators and scavengers 2 mya were twice the size they are today, hominid scavengers would have been very lucky to find a carcass. The hominid scavenger probably would have run out of luck hauling the food back to camp because stealth predators were numerous, fearless and ferocious. Early hominids probably were subject to annual predation at the same rates at which living primates living under natural conditions are today—roughly 8% of their local population.
Independent of the physical improbability, the scavenging scenario is unlikely due to our weak stomachs. Meat begins putrefying immediately after death and attracts parasites, insects, maggots, worms, bacteria and a host of other microorganisms that would have been just as fatal for early hominids as they are for us today.
Moving down the food chain
Rather than moving up the food chain to game meat, early hominids’ first step may instead have been down the food chain where they ingested algae in their drinking water. Terrestrial plant foods available to early Homo were largely hard, dry and bitter. Wild seeds, nuts, roots and leaves would have provided little variation in terms of the four classic tastes; sweet, bitter, salty or sour. Sweet would have been largely missing from their diet, except for the rare occurrence of fruit. Salty would have been missing except for salt licks and they provide an unpleasant intense salty taste, independent of food. The sweet, green algae water would have provided a subtle sweetness and occasionally saltiness. Compared to the rest of the diet available to early Homo, sweet water may have been very attractive.
Early hominids did not intentionally ingest algae to enlarge their brains. Evolution is not volitional and our ancestors probably could not even see the algae in the water because the cells were too small. Algae first become visible as a light cloud. As the cells proliferate, they turn the water green but the individual cells are not visible to the naked eye.
A hominoid tribe on the lee side of an algae lake could have ingested several grams of algae daily in their drinking water. These few grams of algae would have acted as a natural food supplement to supply the essential nutrients, vitamins and antioxidants that provided the green spark for encephalation.
In some settings, algae grow to such concentrations that the green biomass forms mats on the top of the water column that the wind concentrates on the lee side of lakes. These concentrated algae would have been easy to gather for supper or store for later use.
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. The soda lakes produce plentiful natural stands of the high protein and nutrient rich spirulina algae. Spirulina is the bestselling algal nutritive supplement on the market today because it provides a complete set of essential nutrients, including vitamins, minerals, trace elements and antioxidants.
As brains became larger, hominids probably exploited the aquatic plants, fish, crustaceans, amphibians and birds in and around the Rift Valley lakes. Many of these creatures are what they eat and simply concentrate the nutrients from their predominately algae diet. Fish, for example do not synthesize omega-3 fatty acids. Fish concentrate omega 3 from its source – algae.
Taste bud evidence
The human tongue has specialized taste bud receptors for a fifth taste – umami. Umami is a rich flavor constituent found in some protein-rich foods. The unique umami taste which means “good flavor” in Japanese has been isolated and marketed as monosodium glutamate (MSG). In English, umami translates to brothy, meaty or savory. The unique taste is induced by three proteinogenic amino acids: glutamic, inosinic and guanylic. The savory taste would have been largely absent from early hominid diets and would have been very attractive.
Glutamate plays a key molecule in human cellular metabolism. Proteins are broken down by digestion into amino acids, which serve as metabolic fuel for other functional roles in the body. Glutamate is the most abundant excitatory neurotransmitter in the vertebrate nervous system and regulates several brain functions. Glutamate’s role in body functions is so critical that some animals, including humans, evolved a special taste bud call the mGluR4 receptor to taste glutamate. This umami taste is most concentrated in high protein algae and algae feeders such as fin and shellfish, which would have made these foods quite attractive to early Homo. (Today the umami taste can also be found in milk, aged cheese and meat products.) The combination of sweet and umami tastes that were not available to our ancestors from terrestrial foods would have provided a strong incentive for early Homo to eat algae.
Color plays a sizable role in motivating appetite. Most seeds, grains and roots are a dull brown and neither pleasing nor appetizing. Algae have colorful pigments the plant uses to collect solar energy and drive photosynthesis. These pigments provide a spectrum of natural colorings to foods. Unlike modern synthetic colorings, algae pigments are not only colorful but nutritious. Sea vegetables or local freshwater algae would have added attractive color when consumed on their own or when blended with other foods.
Among the many edible algae that would have been plentiful for early hominids in and around Africa were arame, alaria, seawhip kelp, chlorella, dulse, hijiki, karengo, kombu, nostoc, nori, ogo, sea lettuce, sea palm, spirulina and wakame. Algal components would have been available also including agar, alginates and carrageen as well as carotenoids (pigments) such as luten, phycocyanin, zeaxanthin, astaxanthin and phycobiliproteins.
Algae were probably our first food because algae were the best tasting, best texture and most colorful food available. Algae were the most plentiful when humans began gathering food. And they were the most nutritious food source, since most edible algae species provide significant protein and a rich assortment of nutrients as well as essential vitamins and minerals; especially phosphorus, potassium, iron, selenium, copper and zinc.
Algae would have been easy to gather and far less energetically demanding or dangerous compared with hunting. Early hominids had plenty of bitter and sour tastes but were nearly devoid of sweet, salty or savory. Algae would have been attractive as the nutritious plant adding sweet, salt and savory, as well as taste variety to the early Homo diet. Our taste buds that favor algae may have let us down our green path to becoming human.