60秒科学:1 Million Years B.C.: Humans Rare
1 Million Years B.C.: Humans Rare
A study in the Proceedings 1 of the National Academy of Sciences used genomic analysis of modern humans to reveal that the population of our ancestors a million years back was below 20,000. Karen Hopkin reports
At one time or another, you’ve probably said, “It’s a small world.” Well, it used to be much, much smaller. Because according to scientists from the University of Utah, about a million years ago our ancestors numbered fewer than 20,000. The estimate appears in the Proceedings of the National Academy of Sciences.
The scientists based this ancestral census 2 on a reading of modern human genomes. In particular, they tracked the positions of transposable elements. These small pieces of DNA 3 are basically genomic parasites 4. Over time, they’ve spread through our genomes and though they’re still capable of hopping 5 from one place to another, they do so quite rarely. One particular transposon first appeared about a million years ago. And by seeing where these sequences now sit, scientists can get a sense of the size of the breeding population back then.
Their estimate of 18,500 individuals is pretty sparse 6 considering that these early humans were spread across the Old World. By comparison, some 25,000 gorillas 7 and 21,000 chimps 8 were concentrated in Africa alone. So a million years ago, we were essentially 9 an endangered species. Here’s hoping our recovery is permanent.
- He was released on bail pending committal proceedings. 他交保获释正在候审。
- to initiate legal proceedings against sb 对某人提起诉讼
- A census of population is taken every ten years.人口普查每10年进行一次。
- The census is taken one time every four years in our country.我国每四年一次人口普查。
- 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。
- These symptoms may be referable to virus infection rather than parasites. 这些症状也许是由病毒感染引起的，而与寄生虫无关。
- Kangaroos harbor a vast range of parasites. 袋鼠身上有各种各样的寄生虫。
- The teacher's house is in the suburb where the houses are sparse.老师的家在郊区，那里稀稀拉拉有几处房子。
- The sparse vegetation will only feed a small population of animals.稀疏的植物只够喂养少量的动物。
- the similitude between humans and gorillas 人类和大猩猩的相像
- Each family of gorillas is led by a great silverbacked patriarch. 每个大星星家族都由一个魁梧的、长着银色被毛的族长带领着。 来自《简明英汉词典》
- Chimps are too scarce, and too nearly human, to be routinely slaughtered for spare parts. 黑猩猩又太少，也太接近于人类，不可以作为人器官备用件说杀就杀。 来自英汉非文学 - 生命科学 - 医学的第四次革命
- And as nonprimates, they provoke fewer ethical and safety-related concerns than chimps or baboons. 而且作为非灵长类，就不会产生像用黑猩猩或狒狒那样的伦理和安全方面的顾虑。 来自英汉非文学 - 生命科学 - 医学的第四次革命
- Really great men are essentially modest.真正的伟人大都很谦虚。
- She is an essentially selfish person.她本质上是个自私自利的人。