2026年6月英语四级真题（第1套）

Is organic food worth the higher price? It's the classic grocery store dilemma. On the one hand, your family dinner table deserves only the best. On the other hand, your wallet can only stretch so far.

Whether or not to buy organic is a personal decision, said Mike von Massow, professor of Food Agriculture.

Science won't give a clear-cut answer to the question of whether organic food is "better." There are often trade-offs (权衡) and answers become less definitive depending on the product under consideration.

One thing is definitive: Organic and conventionally grown food are equally nutritious. From a nutrition point of view, there is no difference between organic and traditionally grown products.

Organic products don't necessarily have fewer pesticides (杀虫剂)—in fact, they may have more. There is also no big difference between organic and non-organic products from a food-safety perspective. Even organic growers use pesticides. Testing shows little if any pesticide remains on conventionally grown products.

In fact, organic farmers often use larger quantities of pesticide because they can only use the natural variety of insect-killers. Chemical pesticides generally kill a much wider range of pests (害虫) than any single natural pesticide.

The use of animal waste in organic agriculture can also be a factor in the spread of bacteria like E. coli and salmonella. Over the past 10 years, Canada has seen more food-safety recalls for organic products, proportionally, than for conventional products.

On the whole, organic agriculture may have a smaller environmental footprint. That's mostly because the risk of groundwater contamination from organic farming is lower. Organic farmers never used neonics, the controversial pesticides that have been linked to shrinking bee populations worldwide.

Traditional agriculture has been making "dramatic improvements" to reduce its impact on the environment. It isn't a black-and-white picture, though.

Organic farming is much less efficient when it comes to land use, although yields vary considerably depending on the crop. On the other hand, advocates of organic farming argue yields and efficiency could be significantly improved if the food industry devoted as much research and money to organic farming as it does conventional agriculture.

It is still controversial whether we are fundamentally generous or selfish and whether these tendencies are shaped by our genes or environment.

Some evidence points to humans being born cooperative. At later stages in life we routinely work together to reach goals and help out in times of need.

Yet instances of selfish behavior are also plenty. One recent study tested people's willingness to set aside selfish interests to reach a greater good. It found that being selfish was more advantageous than cooperating. The benefit may be short-lived, however. Another study showed that players who cooperated did better in the long run.

It seems that human nature supports both pro-social and selfish traits (特征). Genetic studies have made some progress toward identifying their biological roots. By comparing identical twins, who share nearly 100 percent of their genes, and non-identical twins, who share about half, researchers have found overwhelming evidence for genetic effects on behaviors. In these twin studies, identical and non-identical twins are asked, for example, to split a sum of money with a peer. Such studies often also rely on careful psychological assessments and DNA analysis.

Other work highlights specific genes as key players. My colleagues and I recently identified a gene linked to altruistic (利他的) behavior and found that a particular variant of it was associated with more selfish behavior in preschoolers.

According to evolutionary scientists, cooperative behavior may have evolved first among relatives to promote the continuation of their genetic line. As communities diversified, mutual support could have broadened to include individuals not linked by blood. Another possibility is that humans cooperate to gain some advantage, such as boosting reputation. Finally, evolutionary processes take place at the group level. Groups of highly cooperative individuals have higher chances of survival because they can work together to reach goals that are unattainable to less cooperative groups.

Yet almost no behavior is entirely genetic, even among identical twins. Culture, schooling and parenting are important determinants of cooperation. Thus, the degree to which we act cooperatively or selfishly is unique to each individual and depends on a variety of genetic and environmental influences.