A study says the origin of human is in Botswana. Researchers said they used DNA to find out where modern humans came from. They believe all our roots (根) are in an area of northern Botswana. Humans were there 200,000 years ago. They lived there for at least 70,000 years and then migrated (迁徙) around the African continent. They then started moving to Europe and Asia. Researcher Professor Vanessa Hays, from the University of Sydney, said, “We’ve known for a long time that modern humans originated in Africa about 200,000 years ago.”

The researchers made sure of an area called Okavango as where we came from. There used to be a big lake but it is now a salt flat (盐碱地). People had water, hunting and farmland. Scientists studied DNA from 200 people who live near the area today. They are from the Khoisan people, who live in modern-day South Africa and Namibia. They had a lot of DNA called L0. Professor Hayes explained why L0 is important. She said, “Whenever a Dew migration (迁徙) happens, our L0 records that migration event as a time-stamp. Everyone walking around today comes from this region.”

【小题1】Where did modern humans first come from according to the passage?

A．Botswana.

B．Europe.

C．Asia.

D．India.

【小题2】When did modern humans originate in Africa?

A．About 70,000 years ago.	B．About 90,000 years ago.
C．About 20,000 years ago.	D．About 200,000 years ago.

【小题3】According to Professor Hays, L0 is important because ________.

A．200 people who live near Okavango had a lot of L0	B．People with L0 had water, hunting and farmland
C．People with L0 are from the Khoisan people	D．L0 records people’s migration as a time-stamp

【小题4】Who might write this passage?

A．A tour guide in Africa.	B．An English teacher in junior high school.
C．A scientist of human origin.	D．A student who studies math in university.