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-------------译者:willdemon-审核者:龙腾翻译总管------------

The strange evolution of descending testicles has been explored using a new type of DNA analysis. 

通过一种新的DNA分析方法,睾丸下移的奇特进化特征正在被发现。

A study shows a group of modern African mammals that keep the organs inside of their bodies including manatees elephants and several species of insect-eating rodent evolved the trait relatively recently.

通过研究一系列生殖器长在体内的现代非洲哺乳动物,包括海牛、大象及其他一些以昆虫为食的啮齿类动物,此项进化特征最近才被发现。

The study solves a long-standing debate on whether ascended or descended testicles came first in mammals. 

此项研究终结了一项存在已久的争论,此争论在于探讨哺乳动物的睾丸是先上行还是先下移的。



Most modern mammals including humans keep their testicles in a scrotum to stop them overheating inside the body which would kill sperm.

大多数的现代哺乳动物,包括人类,均是将睾丸存放在阴囊内部以躲避身体内部的高热量,防止热量杀死精子。

But a group of modern mammals in Africa known as the Afrotherians keep their testicles deep inside their bodies - an oddity that has long confounded scientists.

但是一系列被称作非洲兽总目的现代哺乳动物,却将其睾丸存放在体内——此项古怪特征长期困惑着科学家。
[译注:非洲兽总目(Afrotheria)是哺乳动物下的一个分支,包含了金毛鼹科、象鼩科、马岛猬科、土豚、蹄兔目、象及海牛。]

Experts were unsure whether an ancient mammal ancestor passed ascended testicles to the Afrotherians around 100 million years ago or if the group developed the abnormal biology later on.

专家们不确定是否是哺乳类动物祖先在一亿年前将此种睾丸上行的特征遗传到非洲兽总目的,还是它们在后来才演化出此种奇特的生物特征。

Researchers at the Max Planck Institute in Dresden Germany investigated the evolution of testicles using a new DNA technique.

德国德累斯顿市普朗克研究所的研究者们曾通过一项新的DNA技术,来研究睾丸的进化。

Tissues break down over time making them difficult to study in ancient species but the new method gets around this by looking at the DNA of modern animals to work out the protein structure of long-extinct creatures.

器官组织随着时间推移而被分解,因此对古代生物的研究十分困难。但是此项新技术可以规避此种困难,通过观察现代动物的DNA来推算出已经灭绝动物的蛋白质结构。



-------------译者:翀翀麻麻-审核者:龙腾翻译总管------------

They focussed on two key genes known to trigger the development of a ligament that helps pull the testes downward during development.

他们专注于两个已知的关键基因,它们可以触发韧带的发育,从而能帮助睾丸在发育过程中向下移动。

In four Afrotherian species - the tenrec cape elephant shrew cape golden mole and manatee - the two genes were lost around 100 million years ago.

在四个非洲兽总目物种中——马岛猬、象鼩,金毛鼹鼠和海牛——这两个基因大约在一亿年前就消失了。

This happened around the time these species split from the common ancestor they share with the rest of the placental mammals.

这种情况发生在这些物种从它们与其他胎盘哺乳动物的共同祖先分裂的时候。

The genetic mutation that blocked the genes is different in each of the four species suggesting they developed it recently - likely between 20 and 80 million years ago.

阻断这些基因的基因变异在这四种物种中各不相同。这表明它们是最近才发展出来的——很可能是在2000万年到8000万年前。

This shows that the common ancestor of all placental mammals had descended testicles - modern animals with tests inside their bodies evolved them later on. 

这表明所有胎盘哺乳动物的共同祖先都有下移睾丸——睾丸在体内的现代动物是后面进化而来的。

In four Afrotherian species - the tenrec (file photo) cape elephant shrew cape golden mole and manatee - two genes involved in descended testicle were lost 100 million years ago. This showed a key common mammal ancestor had descended testicles

Strangely the two genes were functional in two Afrotherian species - elephants and rock hyrax - and the causes of their testicular retention remain unknown.

奇怪的是,这两个基因在这两个非洲兽总目物种——大象和蹄兔中有起到功能,它们睾丸保留下来的原因仍不清楚。

Researchers said their new technique could help to resconstruct the evolutionary history of other animal body parts in future.

研究人员说,他们的新技术可以帮助在未来重新构建其他动物身体器官的进化史。

'Molecular vestiges offer an alternative strategy to investigate character ancestry' study coauthor Dr Michael Hiller said.

研究的合著者迈克尔·席勒(Michael Hiller)博士说,"分子遗迹提供了另一种调查祖先特征的策略。”

'Instead of investigating a soft-tissue structure directly one can trace the evolution of genes that are crucial for the development of this structure.'

“与直接研究软组织结构不同,人们可以追踪对这种结构发展至关重要的基因进化。”