The Sweet Tooth & Human Evolution

Humans have evolved to have a sweet tooth

I like sweet things. A lot of people do. Have you noticed that when we combine flavors, it’s usually sweet plus something else? Sweet and salty, sweet and sour, sweet and spicy (imagine a chicken wing flavor described as salty and spicy? Definitely not as appealing). Not to mention all the treats that are just straight sugar! The sweet tooth is a part of being human, and it’s actually deeply ingrained in our biology. In this article, we explore the evolutionary purpose behind the sweet tooth, and why the modern diet is causing us problems.

As Mere Apes

There was a time when humans were merely apes. Our evolutionary line is long, convoluted, and honestly, is missing a lot of the picture (which is to be expected when you’re building your family tree out of fossil fragments). Nonetheless, it is widely recognized that humans share an ancestor with the great apes (gorillas, orangutans, chimpanzees, and bonobos).

This ancestor, and many of its ancestors, were frugivores – that means that they primarily ate fruits. Sugary fruits were especially important because more sugar meant more energy.

When our ancestors descended from the trees, eventually walking on two legs and creating tools, many scientists hypothesized that hunting soon followed. But, before humans were hunters, we were gatherers.

In short, humans have been consuming sugary foods since long before we were “human”.

When modern humans emerged from Africa, an estimated 50% of our energy intake came from fruits and vegetables. Genetically, we haven’t changed much since then, but our diets would be unrecognizable to humans from even 1,000 years ago.

How The Sweet Tooth Factors In

Way back when, humans needed a lot more energy to survive. Without e-technology, vehicles, and appliances for every chore, there were an awful lot of demands on our bodies! Hunting AND gathering both took up most of our time.

So why eat sweet?

Sweet fruits and sugars have more energy, and when food was scarce, you wanted to make sure you had the energy to last you to the next strawberry patch. This preference for sweetness is actually seen across many different animal species, and even in bacteria.

It is also possible that this may have been a result of co-evolution: sweet fruits are ripe, which means they have seeds that are ready to be dispersed. When an animal eats fruit, they spread the seeds when they poop, which helps the plant spread.

(There’s an interesting theory about how plants are actually domesticating us to farm them if you care to read more).

This evolutionary link is also related to why kids crave sugar! We know that children are more likely to dip their fingers in the sugar bowl than adults, and this recently has been linked to growth spurts. Basically, children crave sweets because they need that energy to support their growing bodies. Higher sugar cravings have even been connected to taller kids.

This connects back to our long history of limited food access – high-calorie food is essential to survival. Kids who ate more high-calorie food were more likely to live to adulthood and have kids of their own.

Nearly all animals have a sweet tooth, because sugar is an easy and effective energy source and is critical to survival.
Photo by Ahmed Abdulmegid

Where We Are Now

In Canada, most of us have access to all the food we could ever want.

(However, food insecurity is an ENORMOUS issue, especially in Indigenous communities who often lack resources to grow their own or buy healthy foods. As industries pollute or take Indigenous lands for development, these communities lose access to traditional country foods as well.)

Basically, the scarcity paradigm and the need for high-calorie foods to sustain us over long periods of time are not necessary.

At the same time, obesity and diabetes rates have sky-rocketed around the world, as have hypotheses that link our current Westernized diet to diseases from cancer to Alzheimer’s.

Unfortunately, nutritional science is imperfect. How often do we hear one thing (egg yolks are bad!) before it changes to another the next day (there are actually some sources of GOOD cholesterol, like egg yolks!)? This is further muddied by theoretical (and often untested) fad diets, such as Keto, the South Beach Diet, juice cleanses, and much more.

As always, we have access to so much information! But, we are in a state where quantity is overriding quality.

I’m not writing this article as a critique of diet culture (I’ve done that before here). But, sugary foods are more widely available than they ever were before. Their availability has been associated with increases in chronic disease.

I want to shine a light on why that may be true.

Is My Sweet Tooth The Bad Guy?

As we’ve discussed, a craving for sugar is normal. There’s even a pretty good reason for it! But, looking at media, many of us are probably asking if it’s a craving we should be fighting. Is it moral failing to treat yourself to a chocolate bar? Some theories even suggest something like a peach or a banana is borderline unhealthy (looking at you Keto).

Is sugar, or more importantly, my sweet tooth, the bad guy?

Well, it depends who you ask.

Some researchers, like S. Boyd Eaton, claim that humans need to follow traditional diets (fruits, veggies, meat, fat, fiber) – this would mean cutting out many simple carbohydrates. Likewise, low-carb diets have countless personal success stories associated with them! The premise is that humans haven’t really changed since we evolved into “humans” ten thousand years ago. Therefore, our diets shouldn’t change so much either.

A growing number of researchers claim sugar is addictive, like a drug. Once again, it connects back to our ancestors. For our ancestors, when food was scarce, you had to eat as much as you could when you could. Our brains still work this way, but our food is no longer scarce! Alongside increasing sedentism (less active lifestyles), we are getting wayyy more energy than our bodies need.

Addiction, defined as “a complex condition, a brain disease that is manifested by compulsive substance use despite harmful consequence”, is associated with:

  • Decreased control around a substance
  • Social impairment
  • Continued use despite an associated risk
  • A high tolerance and symptoms of withdrawal

Based on these criteria, sugar is addictive! But wait, there’s more.

Defending Sugar

Not all researchers are on board with this villainization of sugar. Why? Simply because sugar has been important to the human diet since before we evolved into humans. Truthfully, a million-plus year of reliance on sugary fruits is a pretty good argument that the picture is much more complex than it may seem.

Edward Archer’s critique is of diet-centrism. He argues that diet alone does not cause health problems. Thus, sugars and starches should not be cut out of our diets. Most of his argument centers around the fact that sugar is essential for rehabilitating malnourished individuals – situation, as usual, weighs heavier than a one-size-fits-all diet. In fact, he suggests that physical activity plays a much greater role in dietary health than diet does!

Likewise, Riccardo Baschetti also argues that sugar is not evil, and the source of sugar needs to be considered. Why? There are many contradictory findings! Sometimes sugar causes health problems, and other times, it does not. Once again, the picture is more complex than initially assumed. Specifically, sugar had more negative consequences when consumed in a solid form than a liquid form.

Baschetti explains this discrepancy using evolution. Again, our ancestors ate A LOT of fruit, and fruit has a lot of sugar. Baschetti further argues that the sugar in fruit was in liquid form (as the solid part of the fruit is mostly fiber), therefore, we are evolutionarily predisposed to digest liquid sugars. It is only SOLID sugars that are unnatural and difficult for our bodies to process.

Our natural sweet tooth is satisfied by fruits, but sugary foods can cause health problems.
Photo by Jonas Kakaroto

The Sweet Tooth: Should It Stay Or Go?

Firstly, we cannot wish our sweet tooth away. So perhaps a better question is, “should we fight our sweet tooth and sugary cravings?”

Based on the research I discussed above, I do want to highlight some recurring themes.

  1. Humans have evolved to eat sugar, like many other animals
  2. The sugar we evolved to eat was primarily in the form of ripe fruits
  3. We evolved to eat sugar when we were living very active lifestyles
  4. Refined sugar and decreased activity are two patterns that have emerged in the past century
  5. Chronic diseases (obesity, diabetes, heart disease, etc) have sky-rocketed in the past century
  6. One size does not fit all, therefore one solution will not be right for everyone

Sedentism (inactivity) and sugar-intake have both been connected to chronic disease by popular media, but the reality is much more complex. Humans need sugar. Humans also need to be active (for many reasons beyond dietary health). Moreover, the kind of sugar we eat (fruits are probably healthier than a candy bar) has an impact on how our bodies respond to that sugar.

What would I suggest (as neither a nutritionist, dietician, or doctor)?

Listen to your body. Eat more fruits. Focus on integrating more movement into your daily routine. But, don’t stress yourself out about finding the perfect diet. The perfect diet is the one that makes you feel good – not about what some influencer on Instagram is telling you to eat.

And, at the end of the day, I fully believe that it is okay to treat yourself to some chocolate!

After all, everything should be enjoyed in moderation, even moderation.

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