VOA科学技术2023--Modern Genome Data Suggests How Homo Sapiens Developed in Africa

Modern Genome Data Suggests How Homo Sapiens Developed in Africa

The human species, Homo sapiens, developed about 300,000 years ago in Africa. The oldest-known Homo sapien fossils were discovered at a place in Morocco called Jebel Irhoud, between Marrakech and the Atlantic coast.

But very few fossils remain from that time. The fossils that do remain come from areas very far apart from one another. Some of them were discovered in Ethiopia, while others were found in South Africa.

That makes it difficult for scientists to know how our species developed and spread across the African continent.

But a new study using genome data from modern-day African populations may help explain that development and spread.

The study suggests that many ancestral groups moved across geographic¹ areas and mixed with each other over hundreds of thousands of years. It also found that everyone alive today can connect their ancestry² to at least two different populations that were present in Africa about a million years.

These results differ from an earlier explanation about our species. That idea suggested Homo sapiens developed in only a single area or mixed with a related species.

"All humans share relatively³ recent common ancestry, but the story in the deeper past is more complicated than our species evolving in just a single location or in isolation," said Aaron Ragsdale. He is a population geneticist at the University of Wisconsin-Madison. He was the lead writer of the study, which appeared recently in the publication Nature.

Because early groups moved and mixed, isolated⁶ groups did not develop. When groups are isolated, they are more likely to become genetically⁷ different from other groups. But the movement and mixing across Africa kept the groups' genetic⁴ material similar.

Scientists looked at genome data from 290 modern-day people, mostly from four populations from different areas in Africa. The four groups were also genetically diverse. The scientists could then connect both similarities and differences among these four groups to genetic connections dating back hundreds of thousands of years.

The groups included the following: 85 individuals from a West African group called the Mende from Sierra Leone; 44 individuals from the Nama Khoe-San group from southern Africa; 46 individuals from the Amhara and Oromo groups in Ethiopia; and 23 individuals from the Gumuz group, also from Ethiopia.

The scientists also included 91 Europeans. This was to measure the possible effect of European and Neanderthal ancestry on the genome. Neanderthals are an extinct human species and were found mostly in Europe until about 40,000 years ago.

Scientists say they have not yet found ancient DNA⁸ from the few fossils dating to the time around 300,000 years ago. However, the genome data from modern populations can help them form a picture of how Homo sapiens developed.

Study co-writer Simon Gravel⁹ is a geneticist at McGill University in Montreal, Canada. He said, "The relatedness among contemporary humans contains a lot of information about this chain of events."

Words in This Story

fossil -n. the hard remains¹⁰ of a prehistoric¹¹ animal or plant that are found inside a rock.

geographic -adj. relating to large areas of land

complicated -adj. having complexity¹²; not simple

evolve -v. to develop over time

location -n. a place

isolate⁵ -v. to make or keep separate from other things or groups

contemporary -adj. relating to things happening now

1 geographic   

adj.地理学的，地理的

参考例句：

• The city's success owes much to its geographic position. 这座城市的成功很大程度上归功于它的地理位置。 来自《简明英汉词典》
• Environmental problems pay no heed to these geographic lines. 环境问题并不理会这些地理界限。 来自英汉非文学 - 环境法 - 环境法

2 ancestry   

n.祖先，家世

参考例句：

• Their ancestry settled the land in 1856.他们的祖辈1856年在这块土地上定居下来。
• He is an American of French ancestry.他是法国血统的美国人。

3 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

4 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

5 isolate   

vt.使孤立，隔离

参考例句：

• Do not isolate yourself from others.不要把自己孤立起来。
• We should never isolate ourselves from the masses.我们永远不能脱离群众。

6 isolated   

adj.与世隔绝的

参考例句：

• His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
• Patients with the disease should be isolated. 这种病的患者应予以隔离。

7 genetically   

adv.遗传上

参考例句：

• All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
• Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物

8 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

9 gravel   

n.砂跞；砂砾层；结石

参考例句：

• We bought six bags of gravel for the garden path.我们购买了六袋碎石用来铺花园的小路。
• More gravel is needed to fill the hollow in the drive.需要更多的砾石来填平车道上的坑洼。

10 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

11 prehistoric   

adj.（有记载的）历史以前的，史前的，古老的

参考例句：

• They have found prehistoric remains.他们发现了史前遗迹。
• It was rather like an exhibition of prehistoric electronic equipment.这儿倒像是在展览古老的电子设备。

12 complexity   

n.复杂(性)，复杂的事物

参考例句：

• Only now did he understand the full complexity of the problem.直到现在他才明白这一问题的全部复杂性。
• The complexity of the road map puzzled me.错综复杂的公路图把我搞糊涂了。