Are humans at the top of the food chain? US media: Look at what you eat

On December 6, the American Fun Science website published an article titled "Are Humans at the Top of the Food Chain?" The full text of the article is excerpted as follows:

It depends on your definition of a predator.

Lions, gray wolves and great white sharks have one thing in common: they are all top predators. Their diet is almost entirely meat, and with the exception of the occasional rare case, these animals have no natural predators —except humans. So, if we are predators of the top predators, does that mean that humans are at the top of the food chain?

The answer depends on how you define "predator," i.e. whether you hunt animals for food or just stop at hunting other animals; and whether you mean prehistoric humans or modern humans.

See what you eat

Sylvan Bonomo, a marine ecologist at the French Institute for Marine Development Research, says that in ecology or in studying the relationship between organisms and their relationships with the environment, the place of humans in the food chain is not based on which animals eat us or which animals we hunt. Instead, he told the Fun Science website, "It's all based on what you eat." According to this definition, the answer is no: humans are not top predators because we don't eat any of the animals we hunt.

Bonomo and his colleagues set out to determine where humans are on the food chain, also known as their trophic level (in the ecosystem). Scientists usually divide the nutritional level into 1 to 5 levels. Plants and other basic producers (using sunlight for energy) are level 1, and herbivores are level 2. At the same time, species in class 3 eat only herbivores, while level 4 species eat only level 3 carnivores, and so on. Species that receive food from multiple nutrient levels, such as omnivores, add 1 to the average nutrient level they eat, followed by an average score. For example, an animal that eats 50% plants and 50% eats herbivores is a class 2.5 omnivore.

Researchers at the French Institute for the Exploitation of the Sea use statistics from the Food and Agriculture Organization of the United Nations on global human food consumption to assign a nutritional grade to every food we eat. According to a 2013 study by the research team published in the Proceedings of the National Academy of Sciences, they found that an average of 80 percent of humans' daily calorie sources come from plants and 20 percent from meat and fish. In this way, our average nutritional level is 2.21, between anchovies and pigs. However, human trophic levels vary around the world. For example, in 2009, Burundians had 96.7 per cent of plants in their diet, and the country's population had a nutritional rating of 2.04. Meanwhile, in the same year, about half of the Icelander diet was meat, with a nutritional rating of 2.57.

Of course, humans are far more threatening to other animals than anchovies and pigs. Some scientists believe that human pressure on other species makes us "super predators" (a term coined by the study's authors to refer to the rate at which humans hunt other species). In a 2015 report published in the weekly Science, scientists at the University of Victoria in Canada compared the activities of human hunters and fishermen to those of other land and sea predators. They found that humans hunt adult prey 14 times faster than other predators.

The food chain is slipping

Bonomo said: "If you take into account the scale of our impact on wildlife, it's huge. However, Bonomo disagrees with the assessment that humans are super predators, and according to his interpretation, super predators are mixed with "top predators". In ecology, predators have a specific definition: they eat animals that are hunted. Bonomo wrote in an email: "I think this article is misleading: it confuses hunting with hunting (hunting and eating). ”

Usually, we hunt wild animals, but don't eat them. For example, the decline in lion populations is mainly due to habitat loss and conflict with humans, who do not want lions to threaten themselves or their domestic animals. Meanwhile, according to a 2017 paper published in the journal Fish & Fisheries, marine fishermen throw away 10 to 20 percent of their total catches. According to the National Oceanic and Atmospheric Administration, these accidentally caught fish are often injured or killed.

Historically, there may not have been much difference between the animals we ate and the animals we hunted.

Researchers believe that for about 2 million years, until the end of the last ice age 12,000 years ago, humans may have been top predators, eating mostly meat. A 2021 paper published in the American Journal of Biological Anthropology suggests that humans are more physiologically similar to carnivores than herbivores, such as having a highly acidic stomach that breaks down complex proteins and kills harmful bacteria, and high body fat that helps carnivores spend a period of diet before the next big hunt.

The researchers write in the paper that some of the changes could lead to a decline in the position of humans in the food chain. The main change is the disappearance of large animals, such as the mammoth. Before and after the mammoth disappeared, humans began to develop techniques that could help them digest more plants, such as stone tools that processed grain.

But even if we were once the top predators heavily dependent on meat, that doesn't mean that modern humans should rise in the nutritional grade. The researchers told fun science that in the past we were carnivores and now we are at the top of the food chain; however, our love of meat is entirely related to the history of carnivorous food in the Pleistocene.

Source: Reference News Network