Humans Aren’t at the Top of Food Chain

This article was originally posted on RealClearScience.

As a species, we have much to be proud of: We have tamed the wild beasts, we have built wonders of the world, and we have landed on the moon. Of course, we believe that we are quite deserving of our privileged position. After all, we won the evolutionary arms race, climbing and clawing and intellectualizing our way to the top of the food chain over the course of millions of years.

But that widely held belief is actually wrong. Humans aren’t at the top of the food chain. In fact, we’re nowhere near the top. Ecologists rank species by their diets using a metric called the trophic level. Plants, which produce their own food, are given a rank of 1. Herbivores, which eat only plants, are ranked 2. The fiercest of meat-loving predators, such as killer whales, rank at 5.5.

So, where do humans rank? A team of French researchers set about calculating the human trophic level (HTL) for every country for which data is available, and their results were published in PNAS. They found that the global HTL average is a measly 2.21, which puts the human diet on par with pigs and anchovies. A trophic level of 2.5 would mean that the human diet was split evenly between plants and herbivores (e.g., cows), so a diet of 2.21 means that we eat far more plants than herbivores. However, as poorer countries such as China and India become wealthier, they choose to eat more meat. As a result, the global HTL has been increasing and will likely continue to do so.

How do countries compare to each other? There are certainly some interesting results in the data. (See figure.)

As expected, Africa and southeast Asia, have relatively low HTLs. The United States and western Europe have relatively high HTLs. But the highest HTLs go to countries like Mongolia, Sweden and Finland, where diets are mostly fish- and meat-based and vegetables are largely an afterthought.

ALF, our loveable, cat-eating friend from the planet Melmac, would feel quite welcome in those societies. In regard to vegetables, he once said, “That’s not food. That’s the stuff food eats.”

Source: Sylvain Bonhommeau, Laurent Dubroca, Olivier Le Pape, Julien Barde, David M. Kaplan, Emmanuel Chassot, and Anne-Elise Nieblas. “Eating up the world’s food web and the human trophic level.” PNAS. Published online ahead of print: 2-Dec-13.