Every year, Arctic terns (北极燕鸥) migrate from the Arctic to the Antarctic — a round-trip of about 80,000 kilometers. New research finds that these far-flying birds use just a few select routes for their travels.

“The Arctic tern is well-known to people as a record holder. To be exact, it holds the world record for the longest migration of any animal, and therefore interacts with a variety of ecosystems along the way,” lead author Joanna Wong, from the University of British Columbia, says.

“They are an indicator species that can tell us so much about the different ecosystems that they travel through,” Wong continues. “If they don’t make it to their destination in one year, then you know there might be an environmental problem somewhere along their route.”

Globally, Arctic terns are declining. Their crossing such a wide geographic range has made it hard for researchers to see where the problem is. “These birds are difficult to study because they are either residing in polar environments, or on the go,” Wong says.

So in order to track them, Wong and her colleagues attached light-level geolocators to the legs of 53 Arctic terns from five breeding colonies (繁殖群落) throughout North America. These geolocators are actually small computers that record surrounding light intensities. “The length of daylight can tell us the latitude (纬度), while the time of solar noon can tell us the longitude, so we are able to estimate positions of birds,” Wong says.

Researchers compared the routes taken by the birds they followed and the migration timing to other Arctic terns that had previously been tracked. They determined that most Arctic terns use common migratory routes. So terns breeding in different areas such as Canada, the United States. Norway, and Greenland, all end up taking similar routes both when they head south and when they return north.

Some other seabirds also use the same paths, which suggests that the routes aren’t specific just to the Arctic terns and that protecting them may be beneficial to other species.

By now, you’ve likely heard of the metaverse(元宇宙).

Last month, Mark Zuckerberg sent everyone running to their dictionaries to figure out what he was talking about when he said Facebook was changing its name to Meta and declared the metaverse not only the future for his company,but the future for the Internet.

Actually, the word and concept aren’t new. Neal Stephenson made up the term in his 1991 science-fiction book Snow Crash, in which people use avatars(分身)to explore an online world. A number of small metaverses have since developed,where people can do many real life things—like working out,meeting with colleagues,or taking a class—but all online and through a pair of eyeglasses that costs around $ 3,500 and other more expensive equipment.

“They are virtual worlds where you feel like you’re inside a cool video game. But it’s so much more than a game because it’s like the Internet,where you’re socially connected and you can do almost anything in the metaverse,”said Jason Moore who teaches virtual art at Brooklyn College and spends a couple of hours in the metaverse every day. “There are currently a handful of mostly unconnected metaverse platforms,including VRChat,NeosVR,and my studio at the college.”

He hopes that cheaper equipment and faster Internet connections might put it within mainstream applications like tourism and provide us with the most powerful educational tool ever invented within a couple of years.

But Frances Haugen,a former Google’s designer,warns that metaverses could harm personal calculation skills and further divide societies as each user stays in their own virtual realities. She is also worried that they are likely to become more addictive than the current social media and rob people of more personal information.

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.