3 . In the mid-1980s, a study compared mtDNA from people around the world. It found that people of African descent (后裔) had twice as many genetic differences from each other than as did others. Because mutations (基因突变) seem to occur at a steady rate over time, scientists were able to conclude that modern humans must have lived in Africa at least twice as long as anywhere else. They now calculate that all living humans descend from a single woman who lived roughly 150,000 years ago in Africa, “Eve”. If geneticists are right, all of humanity is linked to Eve through an unbroken chain of mothers. This Eve was soon joined by “Y-Chromosome (染色体) Adam”, the genetic father of us all, also from Africa. DNA studies have confirmed that all the people on Earth, with all their shapes and colors, can trace their ancestry to ancient Africans.

What seems certain is that at a remarkably recent date—probably between 50,000 and 70,000 years ago—one small group of people, the ancestors of modern humans outside of Africa, left Africa for western Asia, either by migrating around the northern end of the Red Sea or across its narrow southern opening.

Once in Asia, genetic evidence suggests, the population split. One group stopped temporarily in the Middle East, while the other commenced a journey which would last tens of thousands of years. Moving a little further with each new generation, they followed the coast around the Arabian Peninsula, India, and Southeast Asia, all the way to Australia. ''The movement was probably unnoticeable,'' says Spencer Wells. ''It was less of a journey and probably more like walking a little farther down the beach to get away from the crowd.''

Although archaeological evidence of this 13,000-kilometer (8,000-mile) migration from Africa to Australia has almost completely disappeared, genetic traces of the group that made the trip do exist. They have been found in the DNA of native peoples in the Andaman Islands near Myanmar, in Malaysia, and in Papua New Guinea, and in the DNA of nearly all Australian aborigines (土著). Modern discoveries of 45,000-year-old bodies in Australia, buried at a site called Lake Mungo, provide some physical evidence for the theories as well.

People in the rest of Asia and Europe share different but equally ancient mtDNA and mutations. The mutations which they possess show that most are descendants of the group that stayed in the Middle East for thousands of years before moving on. Perhaps about 40,000 years ago, modern humans first advanced into Europe.

4 . As humanity has got richer, animal’s roles have changed. People need their services less than before. Fewer wolves and thieves meant less demand for dogs for protection; the internal combustion engine（内燃机）made horses unneeded; modern sanitation（卫生设备）kept rats in check and made cats less useful. No longer necessities, domestic animals became luxuries. Pet-keeping seems to kick in when household incomes rise above roughly $5,000. It is booming.

The trend is not a new one. Archaeologists（考古学家）have found 10,000-year-old graves in which dogs and people are buried together. Some cultures -- such as in Scandinavia, where dogs have long been both working dogs and companions -- have kept pets for thousands of years. But these days the pet-keeping urge has spread even to parts of the world which have no tradition of sinking into a comfortable chair with a furry creature.

The pet business is growing even faster than pet numbers, because people are spending more and more money on them. No longer are they food - waste - recyclers, fed with the remains that fall from their masters’ tables. Pet - food shelves are full of delicacies crafted to satisfy a range of appetites, including ice cream for dogs and foods for pets that are old, diabetic or suffer from sensitive digestion; a number of internet services offer food, tailored to the pet’s individual tastes.

In the business this is called “pet humanisation” -- the tendency of pet owners to treat their pets as part of the family. This is evident in the names given to dogs, which have evolved from Fido, Rex and Spot to -- in America -- Bella, Lucy and Max. It is evident in the growing market for pet clothing, pet grooming and pet hotels.

People still assume that pets must be working for humanity in some way, perhaps making people healthier or less anxious. But the evidence for that is weak. Rather, new research suggests that dogs have evolved those irresistible “puppy - dog eyes” precisely to affect human emotions. It has worked. The species that once enslaved others now works very hard to pay for the care of its pets. Sentimenta（l 多愁善感的）Americans often refer to themselves not as cat-owners but as the cat’s “mommy” or “daddy”. South Koreans go one further, describing themselves as cat “butlers”. Watch an unlucky dog-walker trailing “his” hound（猎犬）, plastic bag in hand to pick up its mess, and you have to wonder: who’s in charge now?

5 . A day in the life of 18-year-old David Lanster is full of teenage activities: school, baseball practice, homework. And then he starts cooking. "Some nights I'm up until I am making pies, or even later if we're cooking beef," said the student at Ransom Everglades High School in Florida, US.

For the past year, Lanster and Kelly Moran, his classmate, have been hosting fancy dinner parties at Lanster's parents' home. Their meals have 17 courses and are all made by them. Their guests used to give them gifts to thank them, until the pair decided to do something nice for charity. "We got some really great Miami Heat tickets, a nice watch, and many kitchen machines," Lanster said. "But we wanted to make this something positive for people rather than us."

Lanster and Moran focused on Common Threads, a charity that helps to teach kids in poor neighbourhood to cook and make healthy eating choices. The young cooks ask their guests to give however much they want as payment for their meals. It all goes to Common Threads because Lanster's parents cover their food costs. After their last 12-person event, Lanster and Moran gave $1,600 to the charity. Now, they're taking their show out of the kitchen and on the road. Lanster and Moran have started to organise private dinner parties in a similar way: the host pays for the ingredients (食材), and the guests make a donation (捐赠) to a charity.

Outside the kitchen, the two are busy preparing their college applications. Neither is sure what they will do in the future, but they've promised their parents that they'll leave cooking alone until they finish high school.

6 . Sitting around doing nothing used to seem like one of the safest activities possible. Then a few years ago scientists discovered that sitting all clay causes harmful changes that increase your chances of meeting an early end. Even regular workouts didn't fix the ill effects of having your bottom in a chair all workday. Suddenly, sitting became public health enemy number one. However, a new research finds that tiny bursts of intense activity are enough to protect your body from the worst effects of your couch-bound lifestyle.

In the research, the scientists closely observed eight young, healthy volunteers as they sat around. On the first day of the experiment they simply lounged for six hours. On the second day they got up every hour and engaged in five rounds of four seconds of intense workouts on a specialized bike.

"Twenty seconds total exercise an hour sounds like nothing, but the data showed it made a big difference to the subjects' bodies. In short, they didn't exhibit the usual ill effects of having sat all day. This study is small, but it's still both hopeful and relevant. The results suggest that breaking up sitting with frequent exercise can undo some of the effects of being inactive," explains Gretchen Reynolds.

"While the study used a special type of bike developed by sports scientists, the researchers feel similar results are obtainable with home exercise equipment. However, you may have to work for a few more seconds to reach the same level of intensity. You should try to get your heart pumping to its maximum as quickly as possible to ensure the effect. When you find yourself sitting for most of the day, try to rise frequently and move as often during the day as possible and for as many seconds as you can manage," Reynolds concludes.

7 . When we buy something new, we get rid of what’s old. That cycle of consumption（消费）has made electronics waste the world’s fastest-growing solid-waste stream, which is expected to grow as the world upgrades to 5G. However, less than a quarter of U. S. electronic waste is recycled, the rest ending up as rubbish, posing environmental risks.

Part of the problem concerns rule. In states without laws banning (禁止) electronics from the regular trash, electronics often end up in garbage. Even when e-waste rules exist, it’s left to consumers to handle their old devices properly. But recycling them can be a pain. People have to take their electronics to a store, which may pay them for it or charge them to get rid of it. Many consumers simply throw their devices into the trash or throw them in a drawer.

One solution is to make electronics last as long as they once did. Yet, technology companies are speeding the pace of being deserted. “It’s a strategy by producers to force us into shorter upgrade cycles,” said Kyle Wiens, the founder of iFixit, which publishes do-it-yourself repair guides.

Some environmental groups say big companies like Apple and Samsung should pick up the cost of recycling the devices they sell. Lawmakers have passed Extended Producer Responsibility (EPR) laws, which require producers to establish and fund systems to recycle or collect deserted products.

Some companies are increasing their recycling efforts on their own. For example, Apple in 2018 introduced Daisy, a smartphone-recycling robot that can take apart 200 iPhones every hour. But that's a drop in the bucket compared with the 50 million tons of e-waste produced globally last year.

8 . In 2000, when I was around seven years old, my parents, sister, brother, and I were coming back from a T-ball game. There, in our driveway, we saw two adult geese and a small gosling （幼 鹅）. The adults were startled by our return and flew away, but their baby was still too young to fly and couldn't follow. Hours passed, and night fell. The tiny little thing was wandering around our yard, unaware of what could happen.

And then another morning. And still another. Each morning, we would try to drive the goose over to his parents, who kept coming back to our yard. He wouldn't go to them, though, and they wouldn't come close enough to collect him. My sister Joanna decided to call the little guy Peeper, because he would follow us around the yard making a peeping noise, nonstop.

Almost a year passed. My family filled our days with feathery hugs and my dad would throw Peeper up into the air so he could fly a circle around the house.

One evening, my uncle came, and my dad wanted to show him Peeper's circle. He threw him up in the air, but this time, Peeper just flew off. Everyone was very, very sad. We looked for him for days, calling his name, but he didn't come back. Twenty years passed, and Peeper became a fond memory for my family.

Geese are very loyal, and never forget their first home. Even so, it came as a total shock to me when, in 2019,an aging adult goose came to my home. At first, I assumed it was just another goose. After two weeks of the goose coming back repeatedly, it became clear to me that this wasn't a random goose. My old best friend returned, 20 years later.

People desire connection with the natural world. Through Peeper, I have learned so much about myself and about the nature of love.

9 . Shanghai residents passing through the city's eastern Huangpu district in October might have astonished at an unusual sight: a “walking” building. An 85-year-old primary school has been lifted off the ground and relocated using new technology named the “walking machine.”

In the city's latest effort to preserve historic structures, engineers attached nearly 200 mobile supports under the five-story building, according to Lan Wuji, chief technical supervisor (技术总监) of the project. The supports act like robotic legs. They're divided into two groups which alternately rise up and down, imitating the human pace. Attached sensors help control how the building moves forward, said Lan.

In recent decades, China's rapid modernization has seen many historic buildings razed to clear land for high-rise buildings. But there has been growing concern about the architectural heritage lost as a result of destruction across the country. Some cities have launched new preservation and conservation campaigns including, on occasion, the use of advanced technologies that allow old buildings to be relocated rather than destroyed.

Shanghai has possibly been China's most progressive city when it comes to heritage preservation. The survival of a number of 1930s buildings in the famous Bund district and 19th-century “Shikumen” houses in the rebuilt Xintiandi neighborhood have offered examples of how to give old buildings new life. The city also has a satisfying record of relocating old buildings. In 2018, the city relocated a 90-year-old building in Hongkou district, in what was then considered to be Shanghai's most complex relocation project to date.

The Lagena Primary School, which weighs 7,600 tons, posed a new challenge-it's T-shaped, while previously relocated structures were square or four-sided. Experts met to discuss possibilities and test a number of different technologies before deciding on the “walking machine”, Lan said. However, he couldn't share the exact cost of the project, and that relocation costs will differ case by case. “It can't be used as a reference, because we have to preserve the historical building no matter what,” he said. “But in general, it's cheaper than destroying and then rebuilding something in a new location.”

10 . “GOING,GOING, GONE, for $3 to bidder No. 43, the lady in the last row, white hat.” The auctioneer (拍卖师） called out my auction number and location. Delighted at my victory, I took the box and gave it a shake. The contents rattled. Inside were dozens -- maybe even hundreds --of buttons, pins, and other items, all glittering in the sunlight. It reminded me of my mom's button box. As a girl, I'd always enjoyed digging through it, just as my own daughters enjoyed looking through mine.

Then I caught sight of an old woman on a swing, watching the happenings in the yard. I went to chat with her. She told me she was selling almost all her possessions because she was moving to a nursing home in town. Her eyes fell to the button box, and when she looked up, they were glistening with tears. Her fist closed around a delicate pearl button, now yellow with age. She smiled as she told me about the birth of her first child and the special pearl-buttoned outfit that would be worn by five more babies before time wore it thin.

I noticed a large, dark brass   military button and asked her about it. “From my first husband's uniform,” she said. “It's one of the few things I had to remind me of him when he didn't return home alive." As we went through the box together, I pulled a small key from the box, I heard the sharp intake of her breath. It was the key to a music box that played a special love song, she said. She'd lost it years ago. From my hand to hers, I passed the key to her memories.

Hairpins, wooden nickels, and ruby buttons took her further down memory lane. I knew that when I reached my own home, my heart would pull me to my sewing room, where I would rediscover my own lifetime of memories in my own button box.