New Study Provides Evidence of Mysterious Human Species

A new study suggests that a mysterious human species mated with our own species tens of thousands of years ago in Africa.

Researchers say the study provides evidence that present-day West Africans can link about 2 to 19 percent of their genetic¹ ancestry² to an extinct human species. The study describes the species as a "ghost population."

Scientists involved in the research estimated that mating between the two species happened about 43,000 years ago.

Homo sapiens – the species of human that exists today - first appeared more than 300,000 years ago in Africa. The species later spread worldwide.

Earlier genetic research has shown that our species mated with two early human species, the Neanderthals and the Denisovans. The species have been extinct for thousands of years, but modern human populations outside Africa still carry DNA³ from both.

Scientists have discovered many fossil records relating to the Neanderthals and a few from the Denisovans. So far, though, very little is known about the newly identified "ghost population."

Sriram Sankararaman is a human genetics and computer science professor at the University of California, Los Angeles. He led the study, which was recently published in Science Advances.

Sankararaman told the Reuters news agency that "not much" is known about this mysterious species. "We don't know where this population might have lived, whether it corresponds to known fossils, and what its ultimate fate was," he added.

Sankararaman said the extinct species likely split off about 650,000 years ago from the evolutionary⁴ line that led to Homo sapiens.

The study used genetic data from hundreds of West Africans, including the Yoruba people of Nigeria and Benin and the Mende people of Sierra Leone. The researchers compared the data with DNA information from the Neanderthals and Denisovans.

Scientists say they uncovered DNA material in the West Africans that can best be explained by ancestral interbreeding with an unknown member of the human family tree.

Sankararaman said it is no longer necessary to consider only DNA from fossils of early human species to confirm that humans intermixed with them. "We can now see that such events took place by looking at our own DNA itself."

He added that the discovery "opens a new path in understanding the complexity⁵ of human evolutionary history in Africa, where the picture hasn't been as clear."

Words in This Story

extinct – adj. no longer living or existing

ghost – n. the spirit of a dead person that can appear to living people

fossil– n. part of an animal or plant from the past that has been preserved in rock

correspond – v. to be the same or similar

fate – n. what happens to a person, especially when it is something bad

ultimate – adj. final or most important

evolutionary – adj. gradual process of change and development

1 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。

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 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。

4 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

5 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。