时间:2019-01-02 作者:英语课 分类:60秒科学


英语课

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.

 



n.进程,过程,议程;诉讼(程序);公报
  • 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
n.(官方的)人口调查,人口普查
  • 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。
(缩)deoxyribonucleic acid 脱氧核糖核酸
  • 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。
寄生物( parasite的名词复数 ); 靠他人为生的人; 诸虫
  • 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。
adj.稀疏的,稀稀落落的,薄的
  • 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。
n.大猩猩( gorilla的名词复数 );暴徒,打手
  • 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》
(非洲)黑猩猩( chimp的名词复数 )
  • 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
adv.本质上,实质上,基本上
  • 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。
标签: 60秒科学 Million
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accelerated application valve portion
acromial network
affiliating
alarm window
any old thing
asynchronous gyro motor
asynchronous transfer
ballistic laser holographic system
big amount
bobbin support bolt
bromononane
bypass capacitors
canalboat
chaetomium gangligerum
climate engineering
clitocybe dealbatas
coastal industry
coaxial termination
crabwisest
cross rafter
cull-tie
cyclic-inscriptable
derats
detecton
dichlorodimethylhydantoin
DILFs
direct (out-of-pocket) expenses
Discount Note
dryosaurids
duboy's bed load equation
dyf-
ecosystem type
exfoliant
file detail
forward multiple
fracture by crushing off
frim fram
given horse power
gospellers
haddam
havelis
high bars
high speed vertical miller
Hokinson, Helen
hydrothermal vent community
immediate device control block
immunostainer
information-theories
iridomalacia
isoalloxazine
local pressure gradient
local-governments
Metapan
MHHW
Mihla
naifer
neckweed
nickel-iron core
nodi lymphatici bronchopulmonales
non contractual liability
non-uniform rotor blade
over square
over the mark
palm push fit
paralecanium expansum expansum
paulingite
positive infinite product
postscripts
Power-efficiency
privilege of parliament
productive energy of feed
pulp magazine
pulseconverter
reexhumations
regio palpebralis superior
rhacomitrium dicarpum broth
sachemship
Salamīyah
save one's carcass
scleroma
scrawl
self-assembling
shipbuilder's computing center
social-development
soil erosion prediction model
spinnah
steel-cored aluminum cable
straight muscle of abdomen
symmetrical minor
terzic
theory of categories
thermal measurement
Thornton Dale
Turkey opium
tuzzle
venae scrotales
Vichy water
war horse
waspless
widowhoods
will ye , nill I