Hello everyone and welcome to this week's blog post. In this article, I will be answering the question 'how has the human diet changed over the course of history?'. I will begin by describing the diet of the earliest humans, before analysing how it has changed. At the end of this article, I will make some predictions about how our diet will change in the future.
Over the last 3 million years our species, homo sapiens sapiens, has evolved to become a distinct species of the hominid family. During this time, not only have our physical attributes and genetic composition changed, but so has our diet.
Our earliest hominin ancestor was Australopithecus africanus (also known as the Southern Ape). As modern humans, and indeed the entire genus Homo, are thought to be directly descended from this species, it is likely that the earliest human diet was similar to this species.
Since Australopithecus africanus is now extinct, there is no way in which we can observe the species to know for sure our earliest diet. Nonetheless, we can use comparative morphology to make a very good estimate. Comparative morphology works by comparing features we can see from fossils of Australopithecus africanus to modern animals and using these features to deduce what its diet was.
From fossilised evidence, we can see that Australopithecus africanus had incredibly large lower jawbones, much like we can see in gorillas today. Consequently, due to these strong jawbones, scientists believe that our earliest diet consisted predominately of plant material.
As we evolved, our brain size constantly increased - while Australopithecus africanus had a brain size of less than 500 cubic centimetres, human brains today are over 3 times the size. This increase in brain size lends support to the theory that humans slowly evolved to eat motile organisms (as opposed to plants) which required more skill to hunt. This hypothesis is supported by the fact that human mandibles became thinner, suggesting that we started to eat insects and small mammals as well as plants (as meat needs less force to chew).
Further, scientists also discovered that the length of our small intestine decreased while the brain increased in size. While this seems counterintuitive, as a large brain would require more energy so more food to be absorbed, this actually makes sense, as meat has much more fat. Fat is incredibly energy-dense, containing 37.6kJ of energy per 1g of fat. Accordingly, humans need to eat much less meat to get the same amount of energy, so the gut size can decrease while still meeting the higher metabolic demands of the large brain. Additionally, the smaller gut would mean that less energy was required for digestion, so more could be used by the brain.
Unfortunately, while comparative morphology and anatomy allow us to deduce what types of food we ate before writing systems were developed, they don't tell us what in proportions these food groups were consumed. Nevertheless, we can draw parallels to uncontacted tribes to make a reasonably accurate guess about the diet of early humans.
By observing hunter-gather groups across the world, scientists have been able to come up with some ideas about early human diet. Generally, before the age of globalisation where food could be shipped around the globe in a matter of days, our diet consisted of what we could find around us in our environment. For example, the diet of the Hadza (one of the world's last remaining hunter-gatherers) in Tanzania consists mainly of tubers, berries, baobab fruit, plants and honey. Meanwhile, the diet of the Bajau of Malaysia is almost entirely made up of seafood.
In addition, while we don't know the exact time that this occurred, at some point in history humans developed to the ability to control fire. This would have allowed us to cook foods, thus increasing the number of food sources we could use. Additionally, cooking food also allows us to absorb much more energy and nutrients from the food, which may have played a role in increasing human brain size.
Around 12,000-25,000 years ago, agricultural communities began to be established. At this point in history, hunter-gathers began to decline, while the population of farmers exploded. This is because domesticated crops, such as corn, wheat and rice, provided a much more consistent and plentiful supply of food.
Nonetheless, according to the National Geographic Magazine and Clark Larsen (a biological anthropologist at the Ohio State Univesity), human health likely decreased during this period. This was due to numerous reasons, including the fact that our diet became much less diverse. Therefore, since humans were eating the same crops each day, gum infections and cavities in the teeth were much more common. Additionally, deficiencies in minerals such as iron likely led to an increase in diseases such as anaemia.
It is important to remember that, as humans spread around the world and set up different populations our diet, and therefore physiology, has changed. For example, before the domestication of cattle, humans usually were only able to digest milk as an infant and lost this ability as they grew up. However, once humans began to domesticate cattle around 10,000 years ago, they developed the ability to produce the enzyme lactase, which breaks down lactose into glucose and galactose. These simpler sugars can then be absorbed in the gut and used by the body.
The Industrial Revolution of the 19th century marked the next big change in the human diet, due to the rise of manufacturing technology. This technology allowed for certain foods, such as bread, refined sugars and processed foods to be manufactured in bulk and distributed easily. As a result, in this period, carbohydrate consumption increased dramatically.
As a consequence of the industrial revolution, the modern diet is much higher in carbohydrates and sugars than it used to be. Additionally, factors such as increased portion sizes, the increase in 'fast', fried food and a lack of physical activity have meant that the 21st century has seen a surge in 'diseases of affluence'. These include diseases such as obesity, diabetes and coronary heart disease.
In the future, engineered foods will likely constitute a large part of our diet. This includes foods such as carrots, which have been selectively bred to look orange and taste 'better', as well as genetically engineered foods such as golden rice, which has been altered to contain more beta-carotene. This is particularly useful as, over the last hundred years, agricultural practices have led to the number of vitamins and minerals present in fruit and vegetables has decreased significantly. While engineering crops can be beneficial to human health, these benefits must be weighed up against the potential harms, such as reducing genetic diversity.
Furthermore, the human population is projected to grow by an extra 2 billion people by 2050, so crop production will need to increase considerably in the future. Additionally, on average, people are also becoming richer. Richer people tend to want richer foods, such as meat and dairy products. These foods require cattle and other animals to be farmed as well, so crop requirements are likely to increase exponentially as population sizes increase.
Moreover, crop farming and animal farming both require large amounts of water to run. Nevertheless, water scarcity is a major problem already and water shortages are likely to increase in the future. As such, our diet may have to adapt to foods which require less water to produce.
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