環(huán)球英語 — 789：Our Human Journey
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Welcome to Spotlight. I'm Joshua Leo
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And I'm Liz Waid. Spotlight uses a special English method of broadcasting. It is easier for people to understand - no matter where in the world they live.
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People. Men and women, old and young. Today, humans cover almost every part of the earth: jungles, forests, cities, and fields. But, how did we get there? Where did we come from? And why do we look so different?
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Today's Spotlight is on the Genographic Project. This project is an effort to learn more about human history. Researchers want to understand the human journey, where we came from and how we got to where we live today. The project hopes to map human movement from the beginning of human history until now. To do this, researchers are studying the DNA, or genes, of many people all over the world.
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Have you ever wondered about your family history? Who were your first ancestors? And where did they come from?
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Well, facts collected by the Genographic Project seem to point to Africa! Scientists working with the project believe that all people on earth are connected to each other. The Genographic Project states that all of our first ancestors lived in ancient Africa. And from there, people spread all over the earth.
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Spencer Wells is a population geneticist. He is also the leader of the Genographic Project. He told reporters,
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"The greatest history book ever written is the one hiding in our DNA."
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Wells studies the DNA of different people groups all over the world. His research shows that people from all over the world share small parts of their DNA. He thinks that this shared DNA connects people together.
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So, how does the Genographic Project work? How does our DNA connect us together?
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Well, first it is important to understand how DNA works. DNA is a complex chemical molecule. We all have it in the cells of our body. The structure of your DNA contains a long list of information about you. The molecule controls the way that you look. It controls your eye, hair, and skin colour. It controls how tall you are. Some people even believe that DNA affects your behaviour. And no other person can have the exact same DNA as you.
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But, some parts of your DNA will be the same in you and in some other people. Genes are small parts of the DNA molecule. People receive their genes from their parents, half from their mother and half from their father. Parents received their genes from their parents and so on. You share genes with your ancestors who lived many, many years ago.
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Scientists like to study the DNA of tribal native groups best. These people usually mate within their own ethnic group. For example, a man from the Suvadi tribe in Nigeria will almost always have children with a woman from the same tribe. New genes from other ethnic groups are not often brought into the tribe. The DNA within the tribe does not experience much change. So it is easy to study the history of tribal DNA.
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However, sometimes within a tribal group there will be a mutation, or small change in the DNA. Many different things in nature can cause a mutation. Sunlight, pollution, and some chemicals are a few things that can cause a mutation. Mutations happen naturally. People cannot stop mutations.
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Mutations show as a change in the DNA. The change will be visible in the DNA of the person and his children, his children's children, and so on. Scientists choose some of the mutations for careful study. Scientists call these mutations, "markers." A person today could have many "markers" in his DNA. These markers represent his ancestors from the past. Different populations carry their own special markers in their DNA. Scientists can learn a person's genetic history by studying "markers."
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For example, consider what happens if a man leaves his tribe. What happens if he mates with someone outside of the tribe? Their DNA will mix. Their baby will share the parents' DNA. That means the baby will also receive his parents' DNA "markers."
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Now imagine if that child moved to another country to attend university. At university he meets a young woman. She belongs to a different ethnic group. She even has a different skin colour. The two fall in love, get married, and have a baby of their own. The baby's DNA now has "markers" from his mother and his father. His DNA has markers from three different ethnic groups. Scientists could study this child's DNA. They could discover where his parents came from. They could follow the "markers" to learn about the child's ancestors.
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The Genographic Project is interested in "markers" for two reasons. First, "markers" help scientists follow the human path. Imagine a person living in Ecuador. Imagine that his DNA has three particular genetic markers. One of these markers is the same as Native Americans living in the United States. The other marker is the same as people living in Northern Russia. And the last marker is the same as a tribe in Africa. Scientists try to figure out what this means.
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The Genographic Project says that the meaning is very important. First, people with the project believe that studying markers shows us the movement of humans. Our example person lived in Ecuador. He had markers from North America, Central Asia, and Africa. His ancestors may have started in Africa, then travelled through Asia, North America, and into South America, ending in Ecuador. This movement may have taken thousands of years.
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Second, genetic "markers" show connections between people. Facts collected by the Genographic Project show these connections. All the DNA that the Project has tested shares "markers" with Africans - modern day Africans and the remains of ancient African people. That leads researchers to believe that all people groups started in ancient Africa.
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The sharing of genetic "markers" is an important discovery. However, there are some concerns about the project. Native people in some countries do not want to join. They do not trust the researchers. In the past, scientists studied native groups without consent - the native groups did not agree to the studies. These past scientific studies did not bring anything good to the native people. In the United States, and some other places, native groups have argued against taking part in the Genographic Project. They believe that the information could weaken their claims to their land.
However, the Genographic Project has worked carefully with native groups. If a group does not want to give genetic material, researchers go to other groups. They work with communities to share information, so that everyone can learn about their genetic history. Because of this, many native groups HAVE agreed to take part.
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