Why do humans eat meat?

The Question 23rd January 2017

Humans evolved to eat meat. Carnivory shaped Homo sapiens bodies and behaviour. We have forward facing eyes, pointed canine teeth, and a digestive system that can efficiently process meat. We also have big brains we can use to make tools and weapons as well as work collectively to stalk, capture and kill prey items much larger and powerful than an individual human.

The incredible diversity of human diets and cultural attitudes and social norms associated with meat eating also demonstrates that humans are able to consume a wide diversity of meat. Pig, squid, cow, fish, goat, whale, sheep, scorpion. This and many other species feature as regular dietary staples to some people somewhere in the world. At different times in different places, humans have derived valuable protein, vitamins and minerals from eating other animals. Hunting and eating meat are also important socially, with many festivals involving different combinations of ritual killing, preparation and consumption of animals.

But there is no such thing as a free lunch. A meal consisting of large amounts of meat is no exception. The amount of meat that humans currently consume is in many instances neither healthy nor sustainable. Let’s discuss health impacts first.

The World Health Organization has concluded that processed meats as Group 1 carcinogens. This means that there is strong evidence that their consumption causes cancers -- such as stomach and bowel cancer. Red meat probably causes such cancers, which means there is evidence of a link, but not as strong. This does not mean that someone who eats a lot of red or processed meat will get cancer. But they will increase the odds that they do.

The problem is, eating meat can be very pleasurable and given the diversity and availability of meat, then it is very easy to eat too much. If humans have evolved to eat meat, then we may not have a sufficiently evolved off switch for these appetites. Explanations such as this are sometimes used to explain the obesity epidemic sweeping the developed world. Humans are attracted to sweet food and drink because it contains high levels of sugars and so are energy dense. This is exactly what a hunter gatherer needs as they continually roam the landscape seeking out a living. So strong is this desire for sweetness, there are numerous examples of cultures seeking out honey sometimes under very hazardous conditions. For many people, their sweet tooth can be easily sated by visiting the nearest corner store and buying a soda drink or candy bar laden with sugar. Today over one billion people are unhealthily overweight which leads to otherwise avoidable illnesses and in some cases deaths.

If eating too much meat harms us, then it also harms the rest of the planet. To feed the current global population of seven and half billion people, humans rear over 19 billion chickens, over two billion cattle a billion pigs and a billion goats. It’s cattle that are particularly problematic. About one third of all greenhouse gas emissions come as a consequence of agriculture  -- and of those, it is livestock that have the most disproportionate impact. Cattle are ruminants. They digest grass and other feedstock in what are effectively fermentation chamber stomachs. This produces significant amounts of methane which they continually belch. Add in greenhouse emissions from manure and the forests cut down to increase livestock production mean that if cattle production were a nation, it would be one of the biggest contributors to global warming.

There are then the local and regional environmental impacts such as the havoc caused in freshwater and marine ecosystems as animal waste makes its way into the water course. If the increase in meat consumption continues at current rates (not just because of a growing global population but due to increased affluence - as people become wealthier they eat more meat), then these impacts threaten our ability to continue to produce food. In fact, when you do the maths, it is extremely challenging to see how the projected 2050 population of nine billion people could be fed with the current rates of meat consumption.

If we are to ensure that no one goes hungry and limit our impacts on the environment, then we will need to significantly reduce the total amount of meat consumed and how it is produced. This could also dramatically improve health outcomes, not to mention reduce much of the animal suffering that is involved in the industrial-scale animal rearing and slaughter.