2 . The Hadza hunter-gatherers of Tanzania live a life that has not changed much over ten thousand years. They have no crops, no house animals, no permanent shelters. In spite of long exposure to agriculturalist groups around them, the Hadza have maintained their lifestyle.

The story of the spread of agriculture is the story of growing population density (密度). Villages formed, then cities, then nations. Agriculture’s rise, however, came with a price. It introduced infectious diseases, social inequality, occasional famines (饥荒) and war. Professor Jared Diamond of UCLA (University of California, Los Angeles) has called the adoption of agriculture “the worst mistake in human history”— a mistake from which we have never recovered.

Looking at the Hadza, you can see why he came to this conclusion. They do not engage in warfare. They do not live densely (稠密地) enough to be threatened by an infectious outbreak. They have no known history of famine (饥荒). The Hadza diet is more stable (稳定 的) and varied than that of most of the world’s citizens. They live almost entirely free of possessions. They enjoy an extraordinary amount of leisure time, “working” — actively pursuing food — only four to six hours a day.

The chief reason the Hadza have been able to maintain their lifestyle so long is that their homeland is not an inviting place. Recently, however, population growth has brought a flood of people into Hadza lands. The region has generally been viewed by outsiders as unused, a Place in need of development. The Hadza, who by nature are not a combative (好战的) people, have almost always moved away instead of fighting.

There are many things to envy about the Hadza, mostly what free spirits they appear to be. Free from schedules, jobs, bosses, bills, traffic, taxes, laws, social duties and money. But who of us could live like them? It’s incredibly risky. Medical help is far away. One bad fall from a tree, one bite from a snake, and you’re dead. The fact is that it’s too late for us to go back to the Hadza lifestyle. Of greater concern is that soon it may be impossible for them to maintain theirs.

3 . Many cities in the United States could grow their own food locally, raising enough crops and cattle to meet the needs of all residents. This is the finding of an interesting new modeling study from Tufts University, which analyzed the potential for local food production in 378 areas across the US and expected food production.

The researchers found that cities in the Northwest in the United States had the greatest potential to raise their own food. Cities along the Eastern seaside and in the Southwest had the least potential and would not be able to meet all their own needs of diet, even if every acre of agricultural land was used for food production. This makes sense, as many of the cities are coastal and lack room for agricultural spreading.

The study revealed that the United States have a surplus (多余的) of agricultural land for feeding the domestic (国内的) population. Currently, some land is used to raise export crops, but a focus on local food production would start a conversation about how that land gets used. In the words of Peters, lead author and associate professor at the Friedman School of Nutrition Science and Policy at Tufts, “It would be important to make sure policies for supporting local or regional food production benefit conservation and create opportunities for farmers to adopt more sustainable (可持续的) practices. Policies should also recognize the ability of the natural resources in a given local or region and consider the supply chain, including ability for food processing and storage.”

Although it’s a far cry from the current reality, it is a nice thought to imagine cities surrounded by food production operations that transport freshly harvested food to nearby homes, and then make use of the leftover food to fertilize fields and generate heat for greenhouses.

6 . Nowadays organic food has become a fashion. Organic food sales reached a record of $ 45.2 billion in 2017, making it one of the fastest-growing parts of American agriculture. Some people may buy organic food for these reasons like resource cycling and biodiversity, but most people may choose organic food because they think it's healthier. While a small number of studies have shown relationships between eating organic food and reducing risks of being ill, no studies, up to now, have answered the question whether eating organic food can improve health.

According to the United States Department of Agriculture(USDA), organic food does not suggest anything about health. In 20155 Miles McEvoy, then chief of the National Organic Program for the USDA, refused to admit any health benefits of organic food, saying the question has nothing to do with the National Organic Program. Instead, the USDA thinks that organic refers to a production method that increases cycling of resources keeps ecological balance, and protects biodiversity.

I'm an environmental health scientist who has spent over 20 years studying pesticides that do harm to human beings. Several years ago, I was part of the study on whether an organic diet can reduce pesticide exposure. This study focused on a group of pesticides which have always been harmful to children's brain development. We found that children who ate traditional diets had nine times higher exposure to these pesticides than children who ate organic diets.

Last month, I published a small study that suggested a path forward to answering the question whether eating organic food actually improves health. My study got a lot of attention. While the results were novel, they didn't answer the big question. As I told The New York Times in 2003, “What does this really mean for the safety of my kids? But we don't know. Nobody does. It was true then, and it's still true now.”