Deep in the jungle, the Maya built an empire (帝国). And now, scientists are unlocking more secrets about this ancient civilization with the     1     (discover) of 417 cities dating back to 2,000 years ago, said The Washington Post. The cities were found to be connected by 110 miles (177 kilometers) of “highways” in May. They     2     (consist) of the “world’s first-ever extensive system of highways”. The “highways”, as Reuters reported, were     3     (space) stone roadways. Plus, scientists also found pyramids, ball game courts and water     4     (engineer).

The Maya civilization was “far more advanced than we thought”, noted The Washington Post. The new findings showed that they were already busy     5     (create) cities in world history at the time, CNN reported. They did all this in a jungle environment,     6     is rare and impressive. They had to clear rainforest areas     7     (farm) and built large underground reservoirs to store rainwater.

    8    , by 900 BC, many Maya cities were abandoned, calling an end     9     the empire. Scientists still don’t know why. With new forms of technology, maybe this mystery and others could     10     (uncover), telling us even more about this fascinating civilization.

6 . About 5,300 years ago, people from the grasslands of modern-day Russia and Ukraine expanded rapidly across Eurasia. Within a few centuries these “Yamnaya” left a lasting genetic mark on populations from central Europe to the Caspian Sea. Today, archaeologists call them “eastern cowboys” for their livestock herding (畜牧) and highly mobile lifestyle.

But one part of the classic cowboy picture was missing: horseback riding. Although cattle bones and solid carriages have been found in Yamnaya sites, horse bones are hard to find, and most archaeologists assumed people did not start to ride horses until at least 1,000 years later.

In a new study published in Science Advances, researchers say they’ve found the earliest evidence of horseback riding not in the bones of ancient horses, but in their Yamnaya riders. “Everyone has focused on horse remains to get an idea of early horse riding,” says co-author and University of Helsinki archaeologist Volker Heyd. “Our approach was to look at humans.”

The researchers looked at more than 150 bones unearthed in Romania, Hungary, and Bulgaria — the western frontier of Yamnaya expansion. The Yamnaya were well-fed, healthy, and tall; the chemical composition of their bones showed protein rich diets consistent with herding cattle and sheep. But the bones showed signs of distinctive wear and tear. They also showed thick spots on the leg bone consistent with lots of time spent on the horse back. Healed injuries matched the kinds of damage a kicking horse might cause, or what sports medicine doctors today see in riders thrown from their horses.

“In terms of trying to identify people riding horses, I think they’ve done the best job possible bioarchaeologically,” says bioarchaeologist Jane Buikstra. “That doesn’t mean it’s perfect, or convincing, ultimately.”

More samples — including horse bones with signs of riding, such as bit marks or back bone damage from the weight of a rider — would help make the case, says CU bioarchaeologist Lauren Hosek. What the group has found “is really interesting”, she says. “But there’s a lot more work to be done when the risks of drawing the final conclusion are as high as the earliest horse riding.”

A great number of artifacts from eight tombs    1     (unearth) from an archaeological site in Hunan province several months ago. According to the provincial institute of heritage and archaeology, these artifacts, including pottery pieces and bronze    2     (knife), are believed    3     (date) back as early as the Eastern Han Dynasty (25-220).

Six Eastern Han Dynasty tombs are brick tombs, three of    4     might have had owners from the same family, said Chen Bin,     5     member of the archaeological team of the tomb complex under the institute.

It is also the first time that archaeologists    6    (discover)a trench(战壕)4.5meters west of the back chamber of the largest tomb,     7     (measure) about 0.9 meters in width,     8     (approximate)15 meters in length and about 0.1 meters in depth.

“This excavation(挖掘)is    9     great significance to further understanding the funeral customs of people in southern Hunan, as well as the levels of    10     (economy)development and cultural exchanges during the period,” Chen said.

Papermaking technology is one of the four great     1     (invention) in ancient China. Before it was invented, the Chinese people carved or     2    (write) characters on tortoise shells, animal bones, bamboo slices, wooden plates or thin tough silk. Tortoise shells, animal bones and wooden plates were too heavy to use while silk was too expensive.

Till the Eastern Han Dynasty an official named Cai Lun created a kind of paper,    3     (use) bark (树皮) along with old fishnets, rags and hemp waste.     4     paper was suitable for writing and was also very cheap, so it became very popular. Therefore, Cai Lun’s contribution    5     the papermaking was great.

After the Eastern Han Dynasty, the papermaking technology was gradually improved. And then other materials such as bamboo and straw could also be used to make paper. Due to different material various types of paper were produced for different uses. For example, the Xuan paper     6    (make) in Xuanzhou of Anhui Province belonged to the high-quality paper     7    (special) adapted for use in Chinese calligraphy (书法) and painting.

Later, the technology     8    (introduce) to many countries. The invention of paper provides a more     9    (convenience) way for the storage and communication of information,    10     it also has great significance on the development of global civilization.

10 . Scientists have solved a puzzle about modern humans, after research showed that a famous skull of a human ancestor found in South Africa is a million years older than experts thought. This discovery has changed what we know of human history.

The skull, which scientists have named “Mrs Ples”, is from an ape-like human relative from a species called Australopithecus africanus (南方古猿). It was found near Johannesburg in 1947 and, based on evidence from its surroundings, was thought to be between 2. 1 and 2. 6 million years old. This puzzled scientists, because although Mrs Ples looks like a possible early ancestor of early humans, the first true humans had already evolved by the time she apparently lived. For this reason, scientists had decided that Australopithecus afarensis, a similar species from East Africa that lived about 3.5 million years ago, was our most likely ancestor instead.

To get a more accurate age for Mrs Ples, a team led by Professor Darryl Granger of Purdue University in Indiana, US, used a new method to date the sandy rocks where the skull lay. They measured the amount of certain chemicals in rocks, which form at a steady rate when they are exposed to cosmic rays (宇宙射线) on Earth’s surface. Once rocks are buried, these chemicals stop forming and slowly disappear;the surviving amount reveals how much time has passed since the rock (or bones) were on the surface.

The new study shows that Mrs Ples and other australopithecine bones nearby are between 3.4 and 3.7 million years old. This means they lived at the same time as their East African relatives, so that either group could have given rise to modern humans. However, team member Dr Laurent Bruxelles pointed out that over millions of years, at only 2,500 miles away, these groups had plenty of time to travel and to breed with each other. In other words, the groups could quite easily have met, had children together and both been part of the history of modern humans.