Editor's Note: The following is an adapted excerpt of Should We Eat Meat?: Evolution and Consequences of Modern Carnivory, by Vaclav Smil. Wiley-Blackwell, May 2013.
There is no doubt that human evolution has been linked to meat in many fundamental ways. Our digestive tract is not one of obligatory herbivores; our enzymes evolved to digest meat whose consumption aided higher encephalization and better physical growth. Cooperative hunting promoted the development of language and socialization; the evolution of Old World societies was, to a significant extent, based on domestication of animals; in traditional societies, meat eating, more than the consumption of any other category of foodstuffs, has led to fascinating preferences, bans and diverse foodways; and modern Western agricultures are obviously heavily meat-oriented. In nutritional terms, the links range from satiety afforded by eating fatty megaherbivores to meat as a prestige food throughout the millennia of preindustrial history to high-quality protein supplied by mass-scale production of red meat and poultry in affluent economies.
But is it possible to come up with a comprehensive appraisal in order to contrast the positive effects of meat consumption with the negative consequences of meat production and to answer a simple question: are the benefits (health and otherwise) of eating meat greater than the undesirable cost, multitude of environmental burdens in particular, of producing it?
Killing animals and eating meat have been significant components of human evolution that had a synergistic relationship with other key attributes that have made us human, with larger brains, smaller guts, bipedalism and language. Larger brains benefited from consuming high-quality proteins in meat-containing diets, and, in turn, hunting and killing of large animals, butchering of carcasses and sharing of meat have inevitably contributed to the evolution of human intelligence in general and to the development of language and of capacities for planning, cooperation and socializing in particular. Even if the trade-off between smaller guts and larger brains has not been as strong as is claimed by the expensive-tissue hypothesis, there is no doubt that the human digestive tract has clearly evolved for omnivory, not for purely plant-based diets. And the role of scavenging, and later hunting, in the evolution of bipedalism and the mastery of endurance running cannot be underestimated, and neither can the impact of planned, coordinated hunting on non-verbal communication and the evolution of language.
Homo sapiens is thus a perfect example of an omnivorous species with a high degree of natural preferences for meat consumption, and only later environmental constraints (need to support relatively high densities of population by progressively more intensive versions of sedentary cropping) accompanied by cultural adaptations (meat-eating restrictions and taboos, usually embedded in religious commandments) have turned meat into a relatively rare foodstuff for majorities of populations (but not for their rulers) in traditional agricultural societies. Return to more frequent meat eating has been a key component of a worldwide dietary transition that began in Europe and North America with accelerating industrialization and urbanization during the latter half of the 19th century. In affluent economies, this transition was accomplished during the post-WW II decades, at a time when it began to unfold, often very rapidly, in modernizing countries of Asia and Latin America.
As a result, global meat production rose from less than 50 t in 1950 to about 110 t in 1975; it doubled during the next 25 years, and by 2010 it was about 275 t, prorating to some 40 g/capita, with the highest levels (in the US, Spain and Brazil) in excess of 100 g/capita. This increased demand was met by a combination of expanded traditional meat production in mixed farming operations (above all in the EU and China), extensive conversion of tropical forests to new pastures (Brazil being the leader) and the rise of concentrated animal feeding facilities (for beef mostly in North America, for pork and chicken in all densely populated countries).