Evolution of human diet: examining the past and the future

The role meat in our diets is a bit of a classic debate, fueling passionate remarks on both sides of the table. A headline from the World Health Organization, reporting that processed and red meat cause cancer, created a stir in the public media just last month, for example. While most search for a black and white ruling on meat, it's more accurate to say that meat has served varying purposes for humanity at different times. To assess its role in our lives today, we must look at where we've come from and where we're headed. 

Comparative anatomy

Our biology clearly indicates that our evolution has favored the ability to eat both animals and plants.

  • There are several carnivorous indicators, including that:
    • we have enzymes that are able to digest the protein (protease) and fat (lipase) found in meat.
    • we have a vat-like stomach is filled with hydrochloric acid to also aid the digestion of animal compounds.
  • There are several herbivorous indicators, including that:
    • we have salivary amylase, an enzyme specifically for carbohydrates in fruits and vegetables that isn't found in carnivores.
    • we have an exceptionally long small intestine, optimal and specialized for digesting and absorbing plant matter.

By anatomical and physiological definitions, there is no doubt that we are omnivores. 

But... "omnivore" paints a simplistic picture

Labeling humans as omnivores simply indicates that we have the ability to eat both meat and plants. It says nothing about the composition, amount, frequency or consequences of what we choose to eat. To say that we are historically opportunistic feeders may be more accurate, meaning we consume what is most optimal. Optimal options may include what is most available or what was most nutritionally dense, for example. 

Brain and gut evolution

Archeological data indicates that our hominid, smaller-brained ancestors were largely eating fruits, nuts, seeds, and tubers. The expensive tissue hypothesis posits that our brains became larger and more complex because our diets improved in quality, allowing our guts to become smaller and freeing energy to supply an energy-expensive brain. 

  • Hunting contributed to this, propelling social structures and language and positively reinforcing the ability to improve diet quality.
  • Cooking also increased the nutrient availability and digestabilibty of many foods.

How much meat was "caveman" consuming? 

Just in the way that American cuisine is different from any other cuisine around the world, the diets of our ancestors varied depending on what was available at their location. For example, the diet of the !Kung, from the region around Namibia, Botswana and Angola, comprised of approximately 33% animal and 66% from plants, while the Inuit from the Canadian Arctic prospered on mainly fish, seal, walrus and whale meat. But research suggests that for most hunter-gatherer societies, plant sources of food were the staple and animal sources were more varied because they weren't as dependably available. 

Where we are today 

The agricultural revolution and the subsequent industrial evolution have spawned two correlated trends: human productivity and population are booming. Our increased productivity has led to a diet that it is quite different from our ancestors. Essentially, foods are more processed, we eat significantly fewer fruits and vegetables and a lot of meat. Here's a closer look at meat: 

Health consequences 

Industrialization has made our food more nutritionally dense (processed rather than whole foods, hormone and antibiotic injected meat). While our bodies once thrived and benefitted from increased nutrition availability, they are not equipped to handle the nutritional density so rampant in our diets today. The health correlates of this are clear:

Environmental consequences

Married to each of the health risks associated with animal agriculture are the massive environmental consequences. Here's some perspective on the environmental costs of animal agriculture: 

  • To produce 3 lbs of meat 2,644 gallons of water are required.
    • To produce 3 lbs of potatoes, 357 gallons of water are required. 
  • One acre of land can produce 250 lbs of beef 
    • One acre of land can produce 50,000 lbs of tomatoes, 53,000 lbs. potatoes and 30,000 lbs carrots. 
  • Animal agriculture contributes to 14.5% of greenhouse gas emissions.
  • Waste from animal agriculture is creating dead zones in our oceans.
  • 40% of cropland in the U.S. is dedicated for direct human consumption. The other 60% of cropland is dedicated to feed for livestock, which is incredibly inefficient.  
    • The U.S. could feed 800 million people with the feed that goes to livestock. 

looking at the circumstances

Population is projected to reach around 11 billion by 2100. That's four billion more people than our current population. At this rate, food production will have to double to feed all of those mouths. Climate change, which is predicted to reduce crop yields 20-40% in certain regions, complicates this necessity.

Now consider the role that meat has in our future. Meat consumption holds considerable risks to our health. Meat consumption exerts extreme costs on our environment. Meat, especially in the quantity and quality it's consumed today, no longer serves the purpose it did for our ancestors. It's now markedly harmful to us and our environment. We must seriously consider that is it not optimal or possible for conventional animal agriculture to continue its prominent role in human life. 

Taking steps to reduce consumption of products from animal agriculture in general or ensuring that meat is grass-fed and organically grown is a motion towards the health, happiness and harmony for ourselves and the earth.