Mark: Michelle, I have a wild statistic for you. If you took all the humans on Earth and put them on one side of a giant planetary scale, and then you did the same for all our livestock—cows, pigs, chickens—our animals would outweigh us by a factor of more than 20 to 1. Michelle: Hold on, twenty to one? You’re saying the animals we raise for food outweigh the entire human population by that much? That’s… staggering. It feels like we’re living on a farm, not a planet. Mark: Exactly. We live on a planet dominated by the animals we eat. And that mind-boggling fact is at the very heart of the book we're diving into today: Should We Eat Meat? by Vaclav Smil. Michelle: Ah, Vaclav Smil. I’ve heard of him. He’s not your typical food writer, is he? He’s more of a numbers guy, a scientist who looks at the big picture of energy, environment, everything. Mark: That’s the perfect way to put it. He's a Czech-Canadian interdisciplinary scientist, a Distinguished Professor Emeritus, and someone who is famously non-ideological. He’s not here to preach or push an agenda. His entire approach is built on data, and his personal history growing up in post-WWII Europe gave him a very practical, no-nonsense view of resources. He just wants to understand the system. Michelle: Which is probably why his book has such a polarizing reputation. Readers who want a simple 'yes' or 'no' answer tend to get frustrated, while those who love digging into the complexity think it's brilliant. Mark: Precisely. And to understand how we ended up on this planet of livestock, Smil argues we have to look way, way back. Because eating meat isn't just a modern dietary choice; it's arguably what made us human in the first place.

Michelle: Okay, I have to admit, that’s a huge claim. The idea that eating meat made us human sounds a bit like a convenient excuse someone might use at a barbecue. How solid is that argument, really? Mark: It's surprisingly solid, and it goes back millions of years. Smil lays out what’s known as the 'expensive-tissue hypothesis.' Think of the body as having a limited energy budget. For our primate ancestors, most of that budget went to maintaining a very large and complex digestive tract to break down tough, fibrous plants. Michelle: Right, like a gorilla munching on leaves all day. It takes a lot of gut to do that. Mark: A huge amount of gut. But then, some of our hominin ancestors started incorporating a new, incredibly energy-dense food source into their diet: meat. Meat is far easier to digest than raw plants. It's packed with calories, fat, and protein. This dietary shift had a monumental consequence. Michelle: Let me guess. If you don't need a giant digestive system anymore... Mark: You can shrink it. And the energy saved from maintaining that 'expensive' gut tissue could be redirected elsewhere. In our case, it was redirected to the most energy-hungry organ of all: the brain. Our brains started to grow, and grow dramatically. Eating meat didn't just feed our bodies; it literally fueled the evolution of our intelligence. Michelle: Wow. So a smaller gut led to a bigger brain. That’s a wild evolutionary trade-off. Mark: It is. And it wasn't just about biology; it was about social behavior. Smil brings up these fascinating studies of our closest living relatives, chimpanzees. They aren't just passive fruit-eaters; they are active, strategic hunters. Michelle: I’ve seen those nature documentaries. It can get pretty intense. Mark: It’s incredibly sophisticated. In the forests of Africa, male chimpanzees will form cooperative hunting parties to pursue smaller monkeys, like the red colobus. They'll coordinate, with some acting as blockers and others as drivers, to trap their prey in the canopy. It’s a display of teamwork and intelligence. But the most human-like part is what happens after the hunt. Michelle: The sharing. Mark: Exactly. The successful hunters share the meat. It's not a free-for-all. They use it to build alliances, to reward supporters, and even, as studies have shown, to trade for sex with females. It’s a form of social currency. The intellect required to be a clever hunter and a strategic sharer of meat is a foundational part of primate social life. Michelle: So meat became a tool for building complex societies, not just for building bigger brains. Mark: Precisely. And if you look at the archaeological record for early humans, you see this taken to an extreme. Smil tells the story of this incredible site in eastern France called Solutré. For about 20,000 years, during the Upper Paleolithic period, humans used the landscape itself as a weapon. Michelle: What do you mean? Mark: The site is a natural cul-de-sac formed by steep cliffs. During seasonal migrations, groups of hunters would work together to drive huge herds of wild horses up from the valley floor and into this natural trap. The horses, panicked and with nowhere to go, were easy targets. Archaeologists have found the remains of at least 32,000 horses there. Some estimates go as high as 100,000. Michelle: A hundred thousand horses? That’s not just a hunt; that’s an industrial-scale operation for the Stone Age. They must have been getting most of their calories from meat. Mark: For long stretches, they were. It shows that for our ancestors, carnivory wasn't a casual act. It was a cornerstone of survival, requiring immense cooperation, planning, and knowledge of the environment. Michelle: Okay, I’m convinced. Our evolutionary past is deeply tied to meat. But that history feels so distant from my reality of walking into a grocery store. Does our ancient biology really have anything to say about the ethics or environmental impact of a factory-farmed chicken breast today? Mark: That is the perfect question, because the chasm between a Paleolithic horse hunt and a modern supermarket is the central paradox Smil spends the rest of the book exploring. The problem isn't that we eat meat. It's the unprecedented scale and speed at which we started doing it in the modern era.

Michelle: So how did we make that leap? How did something that was once a rare, hard-won prize become so… ubiquitous and problematic? Mark: It was a slow burn, and then a sudden explosion. For most of human history, even after the invention of agriculture, meat was a luxury. It was for feasts, for special occasions. Smil paints this wonderful picture from his own heritage—the traditional Bohemian winter pig killing, the zabíjačka. Michelle: That sounds… festive? And a little grim. Mark: It was both! A family would raise a single pig all year. Then, in the winter, the whole village would come together for the slaughter. It was a community event. The butcher was a respected figure. Every single part of the animal was used—nothing was wasted. They made blood soup, sausages, headcheese. People would take home cuts of meat and fat to last them through the cold months. It was an act of deep connection to the food, the animal, and the community. Michelle: Okay, I can see the respect in that. It’s a world away from grabbing a plastic-wrapped tray of pork chops without a second thought. What changed? Mark: In a word: industrialization. And there’s no better example than the story of the American broiler chicken. Before World War II, chicken was a special-occasion meal. Farmers raised them in small flocks as part of a mixed farm. A chicken in 1935 took about 113 days to reach a market weight of just 1.3 kilograms. Michelle: That’s almost four months. It sounds incredibly inefficient by today’s standards. Mark: It was. But then came a series of scientific "hacks," as you called it. The first major breakthrough was the discovery that adding vitamin D to chicken feed could prevent leg weakness in birds that never saw the sun. Michelle: Wait, why was that so important? Mark: Because it meant you could raise chickens entirely indoors, packed tightly together, year-round. It was the birth of the Concentrated Animal Feeding Operation, or CAFO. Then came selective breeding for rapid growth, optimized feed formulas, antibiotics to control disease in crowded conditions... every stage of the chicken's life cycle was engineered for maximum efficiency. Michelle: So what was the result of all this engineering? Mark: The numbers are just staggering. By 2010, that 113-day grow-out period had been slashed to just 42 days. And in that time, the chicken reached an average weight of 2.6 kilograms—twice the weight in less than half the time. We didn't just domesticate the chicken; we redesigned it into a hyper-efficient protein-producing machine. Michelle: That is both a marvel of scientific achievement and deeply unsettling. We essentially created a new kind of animal to suit our economic needs. And I can only imagine the environmental fallout from raising billions of these birds in massive factory settings. Mark: You’re right. Smil quotes that famous UN report, 'Livestock's Long Shadow,' which identified the livestock sector as one of the top two or three most significant contributors to our most serious environmental problems, from deforestation for feed crops to water pollution and greenhouse gas emissions. The communal, sustainable zabíjačka was replaced by a global system with a colossal environmental footprint. Michelle: So if evolution says 'yes, meat is part of us,' but the modern industrial system says 'Houston, we have a major problem,' where on earth does that leave us? What's the solution Smil proposes?

Mark: This is where Smil’s pragmatism really shines. He argues that the solution isn't a simple, universal ban on meat. He knows that for many people, especially in developing countries, meat is a vital source of nutrients. A complete shift to veganism globally is unrealistic and, in some cases, undesirable. Instead, he advocates for what he calls "rational meat eating." Michelle: 'Rational meat eating.' It sounds so… sensible. What does it actually mean in practice? Is it just a fancy term for 'eat less meat'? Mark: That's part of it, but it's more of a complete framework. It's about being an intelligent, conscious omnivore. The first principle is indeed moderation. The average American consumes a quantity of meat that is far beyond any nutritional necessity. Smil points out that we could cut our consumption significantly without any negative health effects, and likely with many benefits. Michelle: Okay, so less is more. What’s the second part? Mark: The second principle is a war on waste. This connects directly back to that village pig killing. In the modern system, we waste a shocking amount of the meat we produce. Smil highlights some fascinating data from Japan, which, unlike most countries, conducts incredibly detailed surveys of what people actually eat, not just what's available in stores. Michelle: The National Health and Nutrition Survey, right? They weigh everything. Mark: They weigh everything. And their data shows a gap of roughly 35% between the amount of meat supplied to the market and the amount actually consumed. A third of it is lost to spoilage, preparation waste, or simply being thrown away. A rational carnivore, like the villagers at the zabíjačka, uses the whole animal. Michelle: That makes so much sense. It’s not just about producing less, but about honoring what we do produce. What’s the final piece of the puzzle? Mark: It's about being smart about which meats we eat. The environmental impact of different animals varies wildly. Producing a kilogram of beef has a much larger carbon and water footprint than producing a kilogram of chicken or pork. Smil argues for shifting our consumption down the ladder, away from the most resource-intensive red meats. Michelle: And this is something we’re already seeing, right? I feel like chicken has taken over everything. Mark: It has. USDA data shows that since the 1970s, American beef consumption has declined significantly, while poultry consumption has more than doubled. So, in a way, the market is already pushing us toward a more 'rational' pattern, even if it's for economic and health reasons rather than purely environmental ones. Michelle: So, putting it all together, Smil’s vision for the future isn't some radical utopia. It’s about making a series of smaller, smarter choices: eat less overall, waste nothing, and prefer less impactful types of meat. It's a call for intelligence over ideology. Mark: Exactly. It's not a simple 'yes' or 'no' to the question 'Should we eat meat?'. It’s a much more interesting and challenging answer: 'Yes, but we need to be far more thoughtful and responsible about how we do it.'

Michelle: It’s fascinating how this journey through the book takes us from our deepest evolutionary past right to the checkout aisle of the modern supermarket. It reframes the whole debate. Mark: It really does. We started as opportunistic hunters where meat was a key to our survival and intelligence. We evolved into traditional societies where meat was a centerpiece of community and celebration. And then, in the blink of an eye, we industrialized the process to a planetary scale, creating a system of incredible efficiency but also immense environmental and ethical costs. Michelle: And Smil's ultimate point seems to be that we can't turn back the clock to the Paleolithic hunt or the village festival. But we can, and must, move forward with intention. Mark: That’s the core of it. The real question for our time isn't the simple 'Should we eat meat?'. It's the far more complex and urgent question: 'How can we eat meat responsibly and sustainably in a world of 8 billion people?' It’s a design problem, and it requires our intelligence, not just our appetites. Michelle: That’s a powerful way to frame it. So for anyone listening who feels a bit overwhelmed by all this, what’s a rational first step? It feels like the answer can't be to just go vegan overnight, for most people. Mark: I think Smil would agree. Perhaps the first step isn't a drastic change, but a shift in consciousness. Start by asking where your food comes from. Maybe try one or two fewer meat meals a week—'Meatless Mondays' became popular for a reason. Or, even simpler, just commit to eating the leftovers in your fridge. That alone is a powerful act of rational eating. Michelle: It’s about reducing mindless consumption and reintroducing mindful intention. I like that. It feels achievable. Mark: We'd love to hear how all of you think about this. What does 'rational eating' look like in your life? Do you have a strategy that works for you? Let us know your thoughts on our social channels. We’re always curious to see how these big ideas land in the real world. Michelle: This is Aibrary, signing off.