2021年高考英语押题密卷A（新课标III卷）（含听力音频）

It is believed that human story begins in Africa and ends about 200,000 years later with their seven billion descendants (后代) spread across the Earth, living in peace or at war, their faces lit by campfires and computer screens.

In between is an exciting tale of survival, movement, isolation, and conquest, most of it occurring before recorded history. Who were those first modern people in Africa? What routes did they take when they left their home continent 60,000 years ago to expand into Europe and Asia? When and how did humans reach the Americas? For decades, the only proof was found in a small number of scattered bones and artifacts that our ancestors left behind on their journeys. In the past 20 years, however, DNA technologies have allowed scientists to find a record of ancient human migrations in the DNA of living people.

"Every drop of human blood contains a history book written in the language of our genes," says population geneticist Spencer Wells. The human genetic code, or genome, is 99.9 percent identical throughout the world. But while the bulk of our DNA is the same, what's left is responsible for our individual differences — in eye color or disease risk, for example. On very rare occasions, a small change, called a mutation, can occur, which is then passed down to all of that person's descendants. Generations later, finding that same mutation in two people's DNA indicates that they share the same ancestor. By comparing mutations in many different populations, scientists can trace their ancestral connections.

These ancient mutations are easiest to track in two places: in DNA that is passed from mother to child (called mitochondrial DNA, or mtDNA for short), and in DNA that travels from father to son (known as the Y chromosome, the part of DNA that determines a child will be a boy). By comparing the mtDNA and Y chromosomes (染色体) of people from various populations, geneticists can get a rough idea of where and when those groups separated in the great migrations around the planet.

In an effort to fight the "throw-away culture" and promote reuse and repair, the city of Berlin has taken the unique step of opening its own secondhand department store.

This isn't your grandma's thrift shop (旧货商店). It resells perfectly good items that would otherwise be thrown away. A pun on the German words for "department store" and "conserving house", B-Wa(h)renhaus sells a wide variety of products. Far from simply selling old items, the electronic goods have been fixed by expert technicians and come with a year's guarantee. And, to reach more secondhand shoppers, the store was set up right in the middle of the famous Karstadt department store.

With the success of its initial six-month trial run, the city plans to open four more similar operations in other parts of Berlin. By 2030, it hopes to have at least one location in each of Berlin's 12 districts. Since 2008, city policies and educational campaigns have reduced average annual household waste by about 25 pounds per resident. It also recycles about 49% of its mineral construction waste. Currently, the city estimates that 8% of abandoned electronic goods and 6% of huge items thrown away can actually be reused. The goal is to expand the market for these items beyond the usual bargain hunters and eco-conscious consumers.

"Three years ago, we started collecting all kinds of used goods," city spokesperson Dorothee Winden said. "There are lots of things that are well-preserved and functioning but aren't being used anymore. The goal is to give these things a new life with somebody who can use them." The store also includes an education center to encourage more sustainable lifestyles — and also gave an award to a project that recycles school uniforms, so that parents don't have to buy new ones every year.

Scientist at University College London have discovered sets of regulatory genes, which are responsible for maintaining healthy hearing. The finding, made in fruit flies, could lead to treatments for age-related hearing loss (ARHL) in humans.

Globally, one-third of people aged over 65 experience hearing impairment, and while there are thought to be more than 150 genes that may affect hearing loss, there is no unified (统一的) view on how to use these to develop hearing loss treatments.

In the study, published in Scientific Reports, researchers are at the UCL Ear Institute assessed the hearing ability of the common fruit fly across its life span (around 70 days) to see if their hearing declines with age.

A fruit fly's ears share many molecular (分子的) similarities with the ears of humans, making it an ideal tool for the study of human hearing loss.

Researchers found that the antennal ears of fruit flies also display ARHL with nearly all sensitive hearing measures starting to decline after 50 days of age. This made the researchers want to know if there were any "age-variable" genes in the flies' inner ears which have kept the ears healthy for 50 days of their lives.

After closer examination, researchers identified a new set of regulatory genes-homeostasis genes. These genes are often responsible for picking up sound and the overall sensitivity of the ear. Using this information, scientists were then able to genetically modify (修改) the genes and prevent the flies from getting ARHL.

Professor Joerg Albert, lead author of the study, said: "While many studies have been conducted into the hearing function of fruit flies, ours is the first to look at the mechanistic and molecular detail of their auditory life course."

"The fact that these genes are conserved in humans will also help to focus future clinical research in humans and thereby accelerate the discovery of new pharmacological or gene-therapeutic strategies."