Have you ever wondered why we feel hunger? Have you ever wondered why, even when we are full, we find pleasure in eating? The answers to these questions lie in the history of our evolution.


Life on Earth started around 3.8 billion years ago with a tiny, single celled organism. Very gradually, one generation at a time, evolution shaped life around its environment – those most fitted to their surroundings survived and reproduced, while those ill-suited died before passing on their genes. In other words, as the Earth’s environment changed, life itself changed with it. Evidence of this one-way relationship is all around us, and one needs to look no further than the human body to find it:


The first modern human was born around 300,000 years ago in the plains of East Africa. Their long legs allowed them to travel the long distances required for food and water, and their dark skin and light frames protected them from the harsh Savannah heat. As humans migrated North to colder climates, their skin gradually became lighter and their bodies became broader and shorter to conserve heat. Changes in climate and environment were forcing evolutionary changes in human beings.


Evolution and food          

For hundreds of thousands of years all humans had to hunt and gather their own food. Food was often scarce, and man had to expend huge amounts of time and energy on gathering plants and hunting or scavenging animals. When food supplies are unpredictable and energy expenditure high, survival favours those who can eat as much as possible whenever food is available. As such, the reward system in the human brain (a group of structures dedicated to reinforcing evolutionarily advantageous behaviour) evolved to release large amounts of dopamine during eating, often overriding the discomfort caused by overeating. But how and when did this evolutionary advantage become problematic?


Food security

Around 50,000 years ago, humans started to display what is known as modern behaviour. We began developing culture, exhibiting complex, abstract thought and, most importantly, we began creating technology. Suddenly, we were able to change our environment, causing a complete shift in the relationship between life and nature. No longer were we bound to change to fit our environment. Instead, we began changing our environment to fit us.


A key technological development in the rise of human civilisation was agriculture. Just 10,000 years ago marked the beginning of the Agricultural Revolution which completely changed man’s relationship with food. We had learnt that we could control food availability by domesticating plants and animals. Food security had arrived.


Over the following millennia human populations exploded and food production became a key focus. By 7000BC, cattle and chickens had been domesticated. By 3000BC, irrigation begun, greatly increasing crop yields. And by 500BC, ploughing was invented and the need for human labour was drastically reduced… The general trend was that food became more available while the need for high calorie diets previously necessitated by long searches for food dropped.


Jumping forward to the modern developed world and the picture is drastically different still. Most people no longer need to expend any energy to find their food. We can simply walk into a supermarket and buy any food that we desire. Our technology allows for such an abundance of food, in fact, that it is estimated that 1/3 of all food produced annually is lost or wasted. So how does this relate to overeating?


Joining the dots

Looking back on what we’ve just learnt, 10,000 years ago (the blink of an eye in evolutionary terms) food was scarce. We had to work hard to find it, and it had been that way for millions of years. As such, our bodies evolved to reward us for eating as much as was available when it was available. Jump forward to present day and food availability has undergone a tectonic shift. Instead of scarcity we have an overabundance of cheap and readily available food, from meat to vegetables to sweets. Our genes simply have not had the chance to adapt to such a quick change in environment and so those ancient mechanisms which reward us for overeating are still present.


This is why overeating can make us feel pleasure and this is why, as was discussed in our earlier post, ‘Can We Think Ourselves Thinner’, we must exercise mindfulness every time we eat. The human brain is a fickle thing and it can trip us up as much as it can help us. But we are conscious, intelligent beings and, given the right knowledge, we can overcome the obstacles that rapid advancement has placed in front of us. The better we understand why we behave the way we do, the better we understand how to change these behaviours.


A big thank you to Eden Seager for this fantastic guest post! 


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