Recently, you might have succumbed to the urge to eat a frosting-coated donut.
This might have spiralled into five donuts, before you slammed on the brakes and vowed to regain discipline. You might have been a real pro and pinpointed the exact moment your willpower started to fail.
Maybe you were hit with overtime the day before, a difficult task, pushing dieting to the back of your mind. That’s why you instinctively grabbed a donut without thinking.
However, this lapse in discipline actually started 10 million years earlier. It started in the days of unidentified human ancestors, black-coated apes with fierce jaws resembling gorillas but with a dash of human, like something from a parallel universe.
The urge to guzzle sugar has been built into us from day one. The candy industry and advertising mafia didn’t invent sugar addiction: they’re taking advantage of instincts that were already inside of us.
This is part 3 of our history of sugar: the time when there was no history.
Sugar’s instinctive guiding hand
The human taste bud has six main flavours. But for survival in the wild, in the days of uncharted wilderness and mystery around every corner, two receptors reigned supreme: bitter and sweet.
Bitterness is our system for detecting deadly plant toxins. Humans have either 24 or 25 bitter taste receptors (one is genetically determined), detecting different classes of toxins.
A current example is industrial chemicals, with their bitter tang. Before wikipedia, bitterness was vital for avoiding a poison berry or mushroom. We had to rely on the accumulated wisdom of our tribal comrades, but also instinct.
Then there’s sweetness. In short, we evolved our love of sugary foods because sweetness indicates calorific density. It indicates a food that keeps us well fed and plump through the harsh winter, a food that we should prioritise.
The main image of the Ice Age is constant hunting. Every cave painting shows us hunting bison or woolly rhinoceroses. Every few weeks, we had an awesome encounter worthy of any videogame boss battle: taking down a woolly mammoth with nothing but throwing spears and the skills of your fellow tribesmen. A battle of life and death, and in South America, they even had giant sloths (megatharium). In Africa, they had normal elephants, assuming it wasn’t a prehistoric paradise where man and elephant lived in cooperation.
Nevertheless, hunting was unreliable and cavemen would often stagger in completely barehanded. Most archaeological finds are of bones with clear cutting marks on them from stone tools. However, that’s only because well-preserved plant matter remains are nearly impossible to find. Fruit and vegetables probably made up a solid 50% of the prehistoric European diet…
…and back then, there was no 1000 page encyclopedia of wild plants to guide you. The vast wilderness of palaeolithic Europe is stretching out before you, with cave lions patrolling in the distance – which plant do you choose?
The problem is that herbs are often healthy, but not remotely nourishing. Consider kale. It’s loaded with vitamin C (300% of the RDI) and vitamin A (300%), but only contains 55 calories per 100 grams. It’s similar for many herbs that fur-wearing cavewomen would forage. When your life is on the line, when the ice age is biding its time, there’s no room for error, and sweetness was the solution.
With a love of sugar built into our genetic code, we were constantly funnelled towards more calorie dense foods (and still are).
We couldn’t casually walk to the supermarket like today. It was imperative for every hunt to be worthwhile, and the sweetness instincts which haunt us today evolved to make that happen.
We needed energy to hunt wooly mammoths. We needed energy to focus when creeping past the base of an uncontacted Neanderthal tribe in a forest clearing. We needed energy to keep our bodies warm, when shivering in caves on expeditions into the snowy wildlands. We needed energy in case the long rumoured, but never sighted homo erectus showed up.
If broccoli was incredibly calorific, but still tasted like broccoli, with nature forgetting to provide an incentive, would prehistoric gatherers be scrambling to harvest it? No chance.
Sugar – nature’s perfect motivator
But there’s another level to this. The sources of sugar were also particularly difficult to acquire.
Swarms of bees, a giant sloth guarding a berry bush, losing your leg to a crocodile – sugar needed to be so tempting that we’d go the ends of the earth to find it.
For example, consider chimpanzees. In the wild, they’re obsessed with honey, particularly during droughts when their forests fruits shrivel up. There’s an obstacle though: African honey bees are notoriously aggressive compared to European ones. The chimps break open beehives with their bare hands, suffering multiple stings in the process, but scooping out the sweet insides like a cartoon bear. They also use scooping sticks; different chimp societies have been observed using different scooping tools, but the exact same techniques.
With hunter gatherer Africans, meanwhile, approximately 70% of their diet were plant foods. To collect them, they had to travel 4 miles a day on average.
Digging for tubers like the ancestors of sweet potatoes can take 10-20 minutes of hard labour, shifting immovable underground rocks, before cleaning off the soil and cooking it. Nuts were encased in hard shells and had to be carefully picked from trees while standing on a fellow tribesman’s back. With honey, a swarm of angry bees would be guarding the hive! Then you had to drag the honeycomb 20 miles back to your tribal base.
These foods are barely sweet to us now (except honey), but to cavemen and savannah men, whose sweet receptors were totally unsensitised, they would taste like oreos. All three are highly calorific foods, so evolution had to funnel us towards them, regardless of obstacles.
How sugar kept us alive
Speed was important too. The monkeys swinging from treetops 10 million years ago, before gorillas and chimpanzees went their separate ways, faced predators around every corner.
Sugar is a fast burning fuel, so quickly grabbing a fruit dangling high in a tree canopy was perfect for a sudden burst of energy, to dodge the jaws of a swooping eagle.
A caveman prowling for berries in broad daylight is automatically more exposed compared to lying in his cave telling stories about that time he road a hippo like a racehorse. The prehistoric humans with sugar-loving genes would be more likely to survive lengthy hunting trips. It was do or die in the days of yore – a single banana could add the extra 10cm of jump needed to dodge the jaws of an oncoming crocodile.
2 million years ago, there could have been two tribes with a bitter rivalry, at the east and west end of the savannah respectively. Their genetic pool could have been subtly different, and consequently, the east tribe failed to survive. It preferred the taste of protein, which improved their spear-throwing, but delayed their spear-dodging in the heat of battle.
Humans have also evolved particularly dense taste receptors of all kinds, due to our varied omnivorous diets. We have to be discerning as we encounter exotic new plants, which not even 90 year old Grokette ever recalls seeing. Supposedly, we have 10,000 taste buds on our tongues.
Meanwhile, a cow just munches on grass, foliage, and the occasional magic mushrooms. A lion can chase down its prey without much thought required – it’s meat, and it differs little.
Its main concerns are strategical – whether it can get close enough to the gazelle to chase it down. Whether the bison is secretly watching the lion’s approach, and preparing to activate its horns (African farmers are actually painting eyes on the back of their cattle now, to great success).
These supersharp taste buds are another reason why sugar has fully ensnared us.
More sugar secrets
It isn’t just the pleasurable taste of sweetness we’ve evolved. Eating sugar unleashes the euphoric rush of the reward hormone dopamine, the same one that sex and gambling stimulates.
Sugar triggers your own natural opioid production, and increases serotonin generation. These neurotransmitters are why sugar addiction is very real.
It’s all part of a natural reward scheme, to fatten yourself up before the harsh winter comes and your only choice is to hunter a woolly rhino in a thick blizzard reducing visibility to 3 meters.
Except that this 2020, and woolly rhinos went extinct 15,000 years ago. Yet the instincts remain, and so does a global sugar intake 10 times higher than 1850.
The second industrial technology caught up with our love of sweetness, we were in serious trouble. It was OK when we had apples growing in English gardens, or tiny jars of honey for the middle classes. But once the sugar cane was planted across the Caribbean, sparking the booming trans-Atlantic trade, all paths led to today’s sugar overload, fuelled by our genetics.
Genetics illustrate it perfectly
The human taste for sugar is encoded by two genes called taste receptor type 1 member 2 (T1r2) and member 3 (T1r3). Specifically, a reaction between them encodes the receptors vital for detecting sweetness.
Across the animal kingdom, almost all carnivorous animals have no sweet taste. Word on the street is that a cat is the only animal that will reject candy. Cats have a mutation in the T1R2 gene, which makes the sweetness receptor non-functional.
However, other cats like lions, tigers and leopards are exactly the same. T-rexs are believed to have lost their sweet receptors (this might have been a guess), as are dolphins, although they have a better excuse: dolphins swallow their meals whole! As for our primate allies, only the Asian colubine monkey cannot detect sweetness.
Whenever new carnivores evolve, they don’t pass the gene loss to each other. They do it independently, an automatic reaction, as proven by the mutation always occurring in different loci within the TIR2 gene.
Essentially, when becoming a meat eater, the need to be funnelled towards sugar vanishes. It sounds simple and obvious, but it illustrates our modern day sugar woes.
Then we have birds, a special case. When the bird and reptile lineage split 10s of millions of years ago, the entire bird family lost the important T1R2 gene class. But while most birds are carnivores which swoop from the sky, the honey-loving hummingbird (probably a close ally of grizzly bears) is a lifelong herbivore.
How does it detect the sweetness? Apparently, the amino acid taste receptor, which is encoded by T1R1 and T1R3, has mutated to create a new sweet receptor, a unique one in the animal kingdom.
The cravings can appear in reverse too. The guiding hand of sugar is always there, and I’m not talking about those super slow motion adverts of a knife slicing a three layer chocolate cake.
Lingering questions
If evolution is so infallible then why, you might ask, don’t we gravitate towards healthy foods like vegetables?
Because while broccoli and Brussels sprouts might be micronutrient dense – vitamin C, magnesium – they’re not macronutrient dense.
The situation in 2020 is different to 42020BC. With diabetes and heart disease running riot, our top priority is eating real, nutritious plant foods. That’s wise, but it’s not the situation our nutritional homing beacons evolved in.
Back when a sabre toothed tiger would lurk around any corner of an icy ravine, starvation was the enemy. All foods were wild and therefore all foods (well, most) were loaded with phytonutrients, antioxidants and obscure healthy compounds. 5 a day wasn’t a strategy, it was unavoidable.
That’s why kale doesn’t send us into a feeding frenzy where birthday cake does. Evolution isn’t perfect. Just look at the human spine – one million years later, and it still hasn’t adapted to humanity walking upright yet (looks like gorillas are the smart ones). Back problems are humanity’s most common physical malady, and knees are up there too. In 200,000 years, humanity will have probably evolved thick round knees the sizes of footballs.
Evolution isn’t an unbeatable, all-encompassing computer code. It’s a set of characteristics making a species more suited to the environment it evolved in. We’re now removed from that environment, and our eating habits haven’t had time to adapt yet.
Another question is: why hasn’t evolution created a natural aversion to vast quantities of sugar? Mostly because we couldn’t obtain them. Not unless you stumbled through a palaeolithic forest and into a magical, shining circle of beehives, an eternally regenerating source of honey, which became the stuff of legends among distant tribes. No cavemen ate 100 grams of sugar daily, so no genetics telling us not to appeared. There was no evolutionary pressure.
The 21st century is another story though. One day, humans will evolve further, with the top theory being normal bodies but heads the size of boulders. Some people get nausea after swallowing a whole bag of giant cookies; maybe a gene encoding this nausea will mutate and strengthen. Thus, the carriers will be protected against diabetes and heart disease, and their genes will spread around the earth.
The only obstacle is that people tend to get sugar-related disease after they’ve had children. Meanwhile, in the palaeolithic era, life was often short and brutal. The safety of today’s civilisation tends to scupper rapid evolutionary changes.
Conclusion
The very earliest primates dwelled in forests, dining on leaves and flowers. These included the last common ancestor of humans and chimpanzees, possibly called Sahelanthropus, which lived 10-7 million years ago.
Eventually though, they moved into the savannahs for a new ecological niche, where fruits were more dominant. They needed a guiding system. Chimpanzees went even further down the sugar craving road; 50% of their calories are from fruit, the riper the better.
Nevertheless, our evolution is a big cause of today’s sugar epidemic and all the acne it causes.
Not all is hopeless though. Again, an apple would taste as sweet as birthday cake to a caveman. By slashing your intake, you too can upregulate your sweet receptors. This will sensitise you even to wild blackberries. You’ll be amazed at the difference in 10 days.
Thus, you will enjoy the sweetness of sugar without its acne-causing dangers.
Thanks for reading!