文章大意:这是一篇说明文。文章主要说明了通过对古非洲骨骼的基因研究,18000年前的人类基因组被测序,揭示了非洲大陆上的先人如何生活、迁徙和繁殖的信息。文章介绍了研究开展的过程以及发现。
An 18,000-year-old human genome has been sequenced (测定序列) as a consequence of genetic research of ancient African skeletons, showing information as to how the continent’s former people lived, migrated (迁移), and reproduced.
In general, DNA cannot survive in Africa’s heat and damp for long periods of time, and researchers have never previously (先前地) sequenced a sub-Saharan African human genome older than 9,000 years. The authors of this new study, on the other hand, regained genetic material from six people buried between 5,000 and 18,000 years ago.
They also looked at the records of 28 previously reported individuals found at burial sites around the continent, and these 34 people were from three unique source populations originating in northeastern, central, and southern Africa after studying their DNA. This means that the continent was originally inhabited by three distinct groups who must have lived in remote areas for long periods of time. The combination of these three branches, on the other hand, suggests that genetic information was exchanged between the three populations before 20,000 years ago. According to the authors of the study, this process began around 50,000 years ago, because archaeological records suggest an increase in the movement of products over great distances around this time. People are thought to have started having children with partners from far-away places as trading networks grew across the continent.
However, the genomic data shows that this long-range DNA interchange began to decline some 20,000 years ago, implying that humans began reproducing with their immediate neighbors at that time. According to the study’s authors, it may be due to the Last Glacial Maximum, when climate change may have limited people’s movement and pushed them to become more sedentary.
In a statement, study author Jessica Thompson noted, “At first, people found their mates from a far-away place. Further down the line, people valued partners who lived closer to them and were perhaps more culturally similar.” Co-author Elizabeth Sawchuk added, “Perhaps it was because previously established social networks allowed for the movement of information and technologies without requiring people to migrate.”
12. What is the challenge of the DNA study in Africa?
A.Limited technology. | B.Hot and wet climate. |
C.Too many cultural exchanges. | D.Complex human genomes. |
13. What caused the genetic information exchange around 50,000 years ago?
A.Climate change. | B.Archaeological records. |
C.Trades with distant groups. | D.Development in technology. |
14. What is the meaning of the underlined word “sedentary” in Paragraph 4?
A.Stable. | B.Diverse. | C.Active. | D.Mobile. |
15. What can we learn from the ancient social network according to the passage?
A.Distant social exchange was booming 50,000 years ago. |
B.Long-ranged DNA interchange started to occur 20,000 years ago. |
C.Communication with people from similar cultures was always preferred. |
D.Migration decreased when social networks for information became mature. |