3 . One of the most common beliefs among researchers is that humans first arrived in North America 16,000 years ago. According to a recent fossil discovery, that might not be true. The new finding suggests that humans might have arrived in North America far earlier.

In 2013, a damaged mammoth (猛犸象) skull and other bones that looked “deliberately broken” were found. The damage to the bones suggested that humans were the ones who caused it to make tools. Carbon- dating analysis suggested the pieces are roughly 37 ,000 years old. This discovery could shift our understanding of humans ‘earliest existence in North America. These fossils suggest humans killed animals in the area much earlier than 16, 000 years ago.

Previous research led scientists to believe the first humans that settled in North America belonged to the Clovis culture. This was a group of people who left behind carefully made tools 16,000 years ago. However, carbon-dating analysis of the mammoth bones indicates that the site is around 36, 250 to 38, 900 years old. That means it’s the oldest known site left behind by ancient humans in North America.

“That’s not the only interesting thing about the discovery,” said Timothy Rowe, a professor at the University of Texas. “The similar findings supporting an earlier date for human arrival have been mostly ignored. This is because they have contradicted previous research.”

Now, however, he thinks there’s a good chance that researchers will find evidence of humans farther back in time.

The early humans shaped bones into sharp blades, which were used to take apart animals’ remains, according to Rowe. There are also signs that they cooked the animal bones over a fire to melt off the fat. “The real evidence that we have has to do with the breakage patterns, and how thorough they are. They must have used rocks or hammer stones to bust the skeleton apart... These people would use whatever they could,” Rowe told USA Today.

4 . If you travel to nearly any Chinese city in the summertime, you will see people, mostly men wearing T-shirts, sitting out on the sidewalks on low chairs in the shade, playing a game with large round disks of wood.     1     Xiangqi dates back as early as the Warring States period. While experts have different opinions as to who created Xiangqi and how it is linked to Western chess, there is no doubt that by the Tang Dynasty Xiangqi was a popular game in China.     2     And in the 20th century both Sun Yat-sen and Zhou Enlai were big fans of the game.

And, though it may look quite a bit different than Western chess, Xiangqi is actually quite similar in what the pieces can do and how the game is played. Like Western chess, the object of the game is to capture the other player’s “king”.     3    

Unlike Western chess, instead of placing the pieces in squares, the pieces are placed on the intersections of lines. Another big difference between Western chess and Xiangqi is that there is a large empty space in the middle of the board, which the elephants cannot cross.     4     This space refers to an area in China where Liu Bang and Xiang Yu had a life-or-death war. The war was so influential that “the Chu River and the Han Boundary” has become a metaphor(隐喻)referring to any boundary between two opposing armies. When the Chinese people today see this name on the board, the battle scenes come to their mind, as though they are surrounded by thick smoke, able to hear the beating of war drums.     5    

5 . Columbus Day is on the second Monday of October, in the United States.     1    .That means most federal offices are closed.

The holiday honors the first visit to America by the Italian explorer Christopher Columbus. Columbus thought he could reach the Far East by sailing west across the Atlantic Ocean from Europe. He was right, but he was also wrong. He thought the world was much smaller than it is.     2    .

Columbus and his crew arrived in October 1492 on an island they called San Salvador, in today's Bahamas. They explored that island and nearby islands now known as Cuba and Hispaniola.     3    . That is why he called the people who lived on the islands “Indians”。

    4    , even though local plants where he explored were unknown in Europe or Asia, and native people did not understand any languages spoken in the East.

Columbus made several other trips to what was called the New World. He saw the coast of South America and the island of Jamaica.

During his trips, Columbus explored islands and waterways, searching for a passage to the Indies. He never found it.     5    . Yet, he always believed he had found the Indies.