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A recent study proposes a new paradigm for understanding the role of carrion in the subsistence of human populations throughout their evolution. Ana Mateos and Jesús Rodríguez, scientists at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), are the lead authors of the article recently in the Journal of Human Evolution.

This is a multidisciplinary synthesis work in which paleontologists, archaeologists and ecologists from the CENIEH, the Institut Català de Paleoecologia Humana i Evolució Social (IPHES), the Instituto de Investigación en Recursos Cinegéticos (IREC-CSIC), the Instituto Pirenaico de Ecología (IPE-CSIC), the Universidad Miguel Hernández, as well as the Universities of Alicante, Granada and Málaga, reviewed the advantages and disadvantages of carrion consumption for a hominin.

According to the authors, the main advantage of scavenging is that it requires far less effort to obtain food than hunting. As for the disadvantages, it has long been said that scavenging is a scarce and unpredictable resource, that consuming carcasses always carries a high risk of pathogen transmission, and that it involves the danger of being attacked by a predator when trying to access an animal's corpse.

However, findings from ecological research present a very different scenario, challenging the disadvantages that have traditionally been associated with scavenging. Carrion is more dependable than previously thought and tends to be available during periods when other food sources are scarce, making it a crucial resource for surviving times of food shortage.

"When large terrestrial and marine mammals die, they provide tons of easily accessible food, enabling many scavenger species to coexist and feed at the same time," says Mateos, the lead author of the study.

Scavenging animals also exhibit behaviors that minimize the likelihood of contracting a pathogen when consuming or coming into contact with carrion. "Humans have been anatomically, physiologically, behaviorally and technologically adapted from our origins to be efficient scavengers. The acidic pH of the human stomach can act as a defense against pathogens and toxins, and, moreover, the risk of infection was significantly reduced when we began using fire to cook.

"Furthermore, humans can travel long distances with relatively little energy expenditure compared to other mammals, which is essential for locating enough carrion," explains Mateos.

As Rodríguez explains, "Language, even in its beginnings, allowed us to communicate and organize ourselves to look for the corpses of large animals or snatch the prey from a large predator, which we could drive away by throwing projectiles (or simply stones).

"Even the simplest flake tools can be used to cut through the thick hide of large mammals, reach their interior, and efficiently scrape off the remaining meat from an abandoned carcass, while stones used as hammers could break the bones to access the fat and marrow inside."

The authors conclude that, beyond being a fundamental activity for early hominins, humans have always resorted to scavenging as an alternative, highly efficient way of obtaining food, complementary to hunting and gathering plants.

One more eating behavior

When evidence emerged in African archaeological sites in the 1960s showing that early hominins consumed meat, it sparked an intense debate over whether the animals had been hunted by the hominins themselves or had died from other causes and were subsequently scavenged by them.

From that point on, archaeologists and paleoanthropologists devoted their efforts to finding the earliest evidence that hominins were capable of hunting large prey. This gave rise to the notion of a linear progression in human behavior, suggesting that hominins quickly abandoned scavenging once they developed the technological ability to hunt large prey.

This debate was influenced by the view of large predators as the pinnacle of the food chain, with humans taking a place among them, while scavenging has historically been associated with a marginal and less "noble" activity, characteristic of subordinate and primitive species. This view has been refuted by studies carried out by ecologists in recent decades.

"Today we know that carrion plays a fundamental role in ecosystems and that all carnivorous species consume it to a greater or lesser extent. Moreover, many current human hunter-gatherer groups continue to practice scavenging, as one more eating behavior.

"If it has long been said that 'eating meat made us human,' one could equally say that eating carrion made us human," says Mateos.