Wouldn’t it be great to have a genuine craving for some broccoli? Or really want nothing more than to gorge yourself on cellery and kale? Can you imagine if everyone was like this? Heart disease would be non-existent, cancer would be unheard of and everyone would live to a ripe old age. But people don’t like vegetables, instead they want pizza, chocolate, take-aways and anything with lots of fat or sugar in, but these are all bad for us. It seems strange that we didn’t we evolve to like vegetables which would prevent these diseases, but instead crave all the foods which will make us ill.
To understand this, we need to go back to the environment we evolved in, not the environment we live in today. A look at humans 20,000 years ago will show us the world we lived in and that are genetics are designed for, and although 20,000 years is a long time for you and me, in terms of evolution it is a blink of an eye. 20,000 years ago there were no farms or agriculture of any sort, and we lived as hunter gatherers.
Now it is difficult to know exactly what hunter gatherers ate. They would generally have eaten what they can get their hands on, which would depend on the region they lived in, so there would be some broad variation. However, a look at one of the last remaining hunter gatherer societies can give us a very good idea of what it was like.
A tribe called the Hadza are a tribe in Africa which are still living as hunter gatherers today, and are considered to be the last true hunter gatherer societies on the planet. Typical of hunter gatherers, they do not farm or store much food, and they rely on hunting animals and gathering plants for food daily, which means they live a very active lifestyle.
Sugar is a very good source of energy, and it is what the body prefers to ‘run on’ because it is very easily metabolised. When you live an active hunter gatherer lifestyle, high energy and easily metabolised foods are important, so naturally, hunter gatherers have evolved to enjoy and seek out sugar. However, the only source of pure sugar for the Hadza is honey, which as you can imagine is quite hard to find, and even harder to harvest. Most of the sugar they consume will be from fruits, and the Hadza eat a lot of one particular fruit called the baobab (particularly in the wet season) but the sugar content is quite low per portion and it contains lots of fibre, vitamins and minerals – all of which are very nutritious and slow down the rate at which the sugar is absorbed. This avoids the sugar ‘spike’ and following slump that some people experience when eating highly processed sugary foods.
Getting much needed energy and essential micro-nutrients from sweet tasting foods like fruit makes them beneficial to eat, and so hunter gatherers have evolved to seek out and enjoy sweet foods. Interestingly, humans are one of a very few species which cannot produce vitamin C in their body. This is most probably because we ate so much sweet food which is high in vitamin C.
The only significant source of fats for the Hadza and hunter gatherers is animals, and animals don’t like to be caught, which makes fat relatively rare. However, fat is a fantastic source of energy and contains twice as much energy per gram than carbohydrates. The high energy content of fats makes them desirable for the same reason as sugars. Fats also have a number of roles in the body such as promoting a healthy circulatory system, and supporting the immune system.
In addition to this, fats are virtually always accompanied by meat. Meat is the best source of much needed protein which is needed to grow and repair the body, and also contains various other vitamins and minerals which are not very abundant in fruits. This makes wanting to eat fats very beneficial, and so naturally, hunter gatherers evolved to crave fat.
Plants are very easy to find and eat. They don’t run away, and grow all over the place. This means that they were probably eaten quite commonly and were turned to when nothing else (particularly meat) couldn’t be had. They weren’t a high priority because they are low in energy (sugar and fats), and although they would be high in micro-nutrients, these weren’t in short supply in the diet of hunter gatherers. The abundance and low nutritional importance of vegetables meant that craving them never evolved.
As hunter gatherers we have evolved to seek out high energy and nutritious foods because this is important for our lifestyle and survival. These high energy foods would not only provide us with plenty of energy, but also a number of nutrients, and so high energy foods provided a whole nutritious package for survival. Vegetables were much easier to find, and less essential for survival because of their low energy contents, so we never evolved a craving for them to the same extent as we do fatty foods and sugar. This built in sugar cravings lead us to develop highly processed foods which are high in sugars and fats, but devoid of any micro-nutrients.
Had we evolved to crave vegetables, you can guarantee that we humans would have found a way to concentrate that ever it was we craved about vegetables, and produce highly processed and artificial forms of that particular nutrients, which may well have lead to widespread health problems too!
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Historically, sugar and fat were the important foods to eat because they were scarce, and provided much needed energy. We evolved to crave these foods, because they were essential to survive. Plants on the other hand, were readily available, and easy to find, so their nutrients were not essential.