Where did humans come from? An Australian researcher believes that she’s found the answer: river valley in the African country of Botswana (博瓦納).

Professor Vanessa Hayes from the Garvan Institute of Medical Research in Sydney said she and her team have traced (追蹤) modern humans back to small group of people who lived in this valley, according to the BBC.

“It’s an extremely large area, it would have been very lush (蒼翠繁茂的), and it would have actually provided a suitable habitat for modern humans,” she said. She and her team studied mitochondrial (線粒體的) DNA (mtDNA) from people who live in south Africa, such as the Khoisan people. This type of DNA is only passed down from mother to child. This makes it easier to trace one’s ancestry (祖先), according to Business Insider. By tracing mtDNA back through different generations, the team concluded that every person alive today is related to a woman who lived in Botswana.

However, some experts doubt Hayes’ findings, saying that studies like hers are no longer important or necessary. “The idea that we’re looking for a single origin [of modern humans] is out of fashion,” said John Hawks, a researcher at the University of Wisconsin-Madison, US, in Popular Science.

There are many other locations around the world where humans could have gotten their start. It is likely that mankind appeared in many places at the same time. “I increasingly think that there probably wasn’t a single population in which modern humans evolved (進(jìn)化). If that is the case, there is no ‘homeland’,” said Ryan Raaum, who researches African population genetics (遺傳學(xué)) at Lehman College, US.

1.According to Hayes, where did humans come from?

A.Australia. B.Botswana. C.South Africa. D.Latin America.

2.Hayes and her team studied mtDNA because ________.

A.it is the most common type of DNA humans share B.there is a new technology to test mtDNA

C.it is only passed down from mother to child D.both women and men can take mtDNA tests

3.According to Hawks, Hayes’s study is ________.

A.important B.wrong C.fascinating D.unnecessary

4.What is the story mainly about?

A.New findings about the origin of humans. B.New findings about mtDNA.

C.The evolution of humans. D.The habitats of ancient humans..

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