Over the past few months, people in the United States have been watching some unusual television advertisements. They are weird because they advertise a product that no American uses now or is likely to use in the future.

The advertisements show that a product called golden rice will help prevent blindness in millions of children. None of these children live in the United States. They live in countries where white rice forms the main part of the diet. Too much white rice without other food causes lack of vitamin A. This can lead to blindness.

Golden rice has been developed to solve this problem through genetic (基因) engineering. As well as TV advertisements, most news media carried stories on this great scientific development that would help some of the poorest children in world.

It could also save the science of genetic engineering. People in Europe and America have learned more about genetically modified (转基因的) food over past few years. And the more they learn, the less they like what they hear. People like science. And people like to eat food. But they would like the two things kept separate.

The truth is that a child would have to eat 9 kilograms of golden rice every day to get enough vitamin A. And Gordon Conway of the Rockefeller Foundation, which helped the development of golden rice, says that the advertisements have gone too far.

Perhaps the main purpose of golden rice is to get people to accept genetically modified food. The TV advertisements sent a very clear message — if you don’t accept this technology then poor children will go blind. It cost US $50 million get that message across. That would buy a lot of food for poor children.

What do the people who are said to benefit from golden rice think of being part of this great scientific and social argument? Nobody knows. Nobody has asked them.

Researchers at the University of British Columbia in Canada have found that humans grew cacao trees and used cacao starting around 5,300 years ago. But the new discovery shows people grew cacao trees about 1,500 years earlier than what was known before. The researchers found evidence of cacao’s use at an old village in the highlands of southeastern Ecuador. Time has had little influence on the village, so they were able to find a lot of evidence of the use of cacao after examining the remains of very old objects at the Santa Ana-La Florida archaeological site.

The researchers found very small pieces from the cacao tree in the remains of containers and other objects. They also found a substance in the cacao tree but not in is wild relatives. This suggests that humans grew the tree for food purposes.

But thousands of years ago, cacao was used to make drinks. The objects on which cacao was found suggest a lot about how people used the substance at that time. They clearly drank it. There is no decided history of indigenous populations in South or Central America using cacao to make chocolate the way people do now. By the time Spanish explorers arrived in Central America in the late 1400s, people were using it to make hot and cold chocolate drinks with spices. By the 1580s, Spain began buying cacao from abroad and spreading it to other European countries. By the 1800s, technology developed in the Netherlands made it possible to turn cacao into a solid chocolate product.

Laiskonis, who teaches chocolate-making classes at the Institute of Culinary Education, introduces his students to the history of chocolate. He tells his students, for example, about a recipe from the 1600s that mixed Mayan and Aztec types of cacao drinks with European influences. Laiskonis said chocolate is “something that’s always been changing.”

The first mouthful of “cultivated” meat is both remarkable and dull. In a homely kitchen at the California headquarters of Eat Just, a startup, a-card-sized slice of meat, served with a sweet-potato puree, mushrooms and some pickled peppers, has been grilled. The meal is remarkable because the meat was grown in a lab. It is ordinary because the texture, taste, look and smell of the meat is almost identical to that of chicken.

Broadly speaking, there are two ways to make cultivated meat. One option is to put the cells in a stainless-steel tank, called a “bioreactor,” which is filled with a nutrient-rich liquid that is often from cow embryos (胚胎). The cells multiply, and after a month or so a meaty slurry can be harvested and turned into minced-meat products such as chicken nuggets (鸡块).The alternative is to place the cells on a frame. That encourages them to grow into a certain shape, and is used to create more fibrous meat, such as steaks.

The cultivated-meat business hopes that this experience will become more common. In June, Eat Just and Upside Foods, became the first two companies to win regulatory approval to sell cultivated meat in America. A handful of firms already do so in Singapore. In total, around 160 firms are trying to bring cultivated meats to market.

But doing so will be challenging. In America, diners without the benefit of a press card can find cultivated meat in just two restaurants. Years ago the industry was bullish. McKinsey guessed it might grow to $25 billion worldwide by the end of the decade. But that hope is fading. Most companies are now more focused on producing hybrid meats, which combine cultivated animal protein with protein from plants such as soya or wheat because of stubbornly high costs and troubles with mass production.

In some rich countries, plenty of people say they want to reduce their consumption, ether for ethical reasons or environmental ones. Lab-grown meat may, for some consumers, be less ethically worrisome than eating animals. And the early success of plant-based meat alternatives gave investors hope. Earlier this year, Vow Food, an Australian start-up, created a “mammoth meatball”, mixing ancient DNA recovered from frozen mammoth remains with that of modern-day elephants.