This blog post is a summary of Vaclav Smil's paper Eating Meat: Evolution, Patterns, and Consequences. Although I eat meat, it should be noted that I am not an expert in meat. Thus, please take this summary with a grain of salt.
As with any scientiﬁc article, the information may be wrong or out of date. To note, this paper was published in 2002. Keep that in mind when I use words like “currently.”
Humans evolved to eat meat–and thus we should include at least some meat in our diet. Yet, meat isn't a requirement because humans can make up the needed nutrition from other sources.
We eat meat for more than just nutritional requirements. To this day, meat acquisition is still considered a sign of success, and we share meat with others to create social bonds.
The author lays out an ultimatum: meat is not neutral. Some cultures have revered killing and eating animals. Others, particularly religious aesthetics, have abhorred eating meat.
Due to the way meat is produced, a civilization obsessed with meat puts itself at risk for spreading disease.
The West tends to limit the scope of what we mean by meat. For afﬂuent countries, it usually only refers to the meat of domesticated mammals and birds.
Historically, humans have consumed more than just proteinous muscle. Culture has gotten progressively more choosy over time about which parts of the animal are acceptable to eat.
Fatty meats provide more energy and palatability. This is partially why greasy fast food is addicting–it's full of fat.
The author concludes that afﬂuent countries are consuming too much meat. In a sense, humans used to complement their diets with meat. We now dominate our diets with meat.
Evolutionary heritage and preagricultural meat consumption
A long time ago, humans learned how to use ﬁre. The ability to cook meat greatly increased ancient humanity's meat-eating opportunities.
Humans learned to kill large herbivores because they provided a lot of fatty, energy-dense meat. These herbivores could be killed without using weapons–just simply drive them off a cliff.
The origins of human intelligence are linked to meat. Cognitive ability was likely needed for humans to coordinate the sharing of meat within a group.
Humans have abnormally large brains. To support the growth of this organ, it is hypothesized that another organ had to be downsized. Possibly, our gastrointestinal tracts were shrunk to give more metabolic energy to the brain. With a smaller tract, an animal can't digest as effectively. Thus, this change would have caused humans to seek more energy-dense food.
Different human cultures ate different amounts of meat, and thus there was a wide range of per-capita meat/protein intakes. Meat in traditional agricultural societies About 10,000 years ago, humans learned how to farm. Farming food increased the population density but simultaneously decreased the average quality of nutrition.
Even among rich European households in the late 18th century, eating meat was quite rare. Peasants may only have eaten meat 2 or 3 times a year.
Around the 1930s, meat supplied only around 2% of all food energy.
Modern dietary transition and its outcomes
Diets started to change in Europe around the mid 19th century. Markedly, there was a dramatic increase in meat consumption, which was driven by the combined forces of improved agricultural productivity, rapid industrialization, and widespread urbanization.
The pace of worldwide dietary change increased after World World II because mechanized agriculture was aggressively subsidized.
The ﬁrst refrigerated shipments of meat began in the 1870s, which helped the expansion of worldwide meat trade.
In the Western world, we mostly only eat beef, pork, or poultry. The consumption of other meats has been steadily declining over the years.
By the end of the 20th century, the population of afﬂuent countries represented only one-ﬁfth of the global total but produced and consumed two-ﬁfths of all red meat and three-ﬁfths of all poultry.
To produce more meat, humans ironically need to produce more grain to feed the animals. Thus, meat is not a perfect substitute for plants; they're complements.
Animal feeding requirements
There is a tradeoff when feeding grain crops to animals. For example, if foodgrains were cultivated instead of feed crops, we would produce more digestible energy and protein. Yet, animals produce higher quality protein.
Cows suck at turning feed grain into meat. They consume about 50% more energy than pigs. Chickens are the best converters of plant-to-animal protein–at about 20% efﬁciency.
Overall, the three major animals–cows, pigs, and chickens–are extremely inefﬁcient at creating protein. About 80 to 96% of plant protein consumed is not converted to animal protein.
Environmental consequences of meat production
Nowadays, humans eat so much meat that domestic animals have become the dominant class of vertebrates on Earth. In summary, there's a lot of cows.
With current crop yields and feeding practices, the entire world cannot eat meat at the same rate as the afﬂuent countries. To achieve meat-eating for all, we would need to make advances in bioengineering.
The number of feed crops fed to animals could feed approximately 3 billion additional humans. In a way, it's tempting to try switch people to a mostly plant-based diet. The only problem is that humans like eating meat and would be unlikely to change our diet preferences in mass.
One needs large amounts of water to raise animals and grow feed crops. Thus, meat/grain trade can beneﬁt countries with scarce water resources. This situation can potentially set up a comparative advantage in trade for water-rich producers.
The main factor limiting the size and density of animal production is our inability to dispose of wastes effectively.
Health implications of meat production and consumption
Most of the animals we eat are social animals–and this leads to various ethical dilemmas. Modern farming techniques don't exactly take good care of the animals.
Meatpacking is one of the most dangerous occupations in the country. In 2000, about 25% of meatpacking employees, or about 4 times the private industry average, had nonfatal injuries or illness. Serious injuries occur at about 5 times the private industry average.
Obesity in adults was stable between 1960 and 1980–at about 25% of the population. In the 1980s, this percentage rose by 8 points. By the 1990s, every third adult in the United States was obese.
Many meals in the United States are high in fat. The author blames beef's high lipid content and our preference for fast food.
We use more antibiotics on animals than on humans. This practice could potentially lead to bacteria gaining immunity to essential antibiotics.
During the last four decades, humans have tripled our meat production.
Over time, our diets have become less disciplined–which has gone hand-in-hand with obese people claiming to be victims.
There is no scientifically defensible reason for strict vegetarianism. Conversely, there is no defensible reason for the amount of meat currently prevailing in Western diets. These meaty diets do not make people healthier or prolong their lives.