VOA标准英语2012--Could Rising Temperatures Mean Smaller Mammals?

Could Rising Temperatures Mean Smaller Mammals?

Scientists say in the ancient past, higher temperatures meant smaller mammals. They’re studying how a brief, but dramatic climate change event affected¹ body size.
It’s called the Paleocene-Eocene Thermal² Maximum or PETM for short. It took place 56 million years ago and lasted about 175,000 years. That’s a long time in human terms, but a blink of an eye in the geological record.
Jonathan Bloch said a lot happened back then.
“We had known it was a really unique event for a while in the sense that it was a very rapid, large scale global warming event. And it marks one of the most important moments in mammalian evolution in the sense that we see the first occurrence of several modern orders of mammals, including the primates³ that are clearly traceable as the direct ancestors of the group that we’re a part of, as well as the ancestors of horses, the ancestors of cows and hippos and camels,” he said.
Bloch is associate curator of vertebrate paleontology at the Florida Museum of Natural History at the University of Florida. He and colleagues from eight institutions were collecting fossils in the state of Wyoming’s Bighorn Basin.
Tiny horses
Teeth of miniature dog-sized horse that lived in Wyoming 56 million years ago.
“For the past 9 years, we’ve been slowly, slowly collecting teeth, and sometimes more than teeth, fragmentary jaws⁴, of the first horses to come in. And what we started to find was something pretty surprising to us. We had known that the horses that came in initially⁵ with that event 56 million years ago were very small, about the size of a small dog. But what we didn’t realize was that in fact when they came in they were a little bit larger than we had expected; and that through the climate event they became about 30 percent smaller and then became larger again,” he said.
Then, Bloch said, fellow researcher Ross Secord, now at the University of Nebraska, took a closer look at what are called oxygen isotopes⁷. These were found in the teeth of the horses. The relationship between oxygen and carbon in these isotopes can provide much information.
“What he showed was that exactly coincident with this body size change that we had documented there were shifts in the oxygen isotope⁶ that showed it was getting warmer as the horses were getting smaller. And then as the horses became larger again it became cooler,” he said.
They concluded that temperature change resulted in smaller horses.
Jonathan Bloch of the Florida Museum of Natural History
Climate itself is changing through this interval⁸ by as much as 10 degrees [Celsius] at high latitudes⁹ and perhaps as low as 5 degrees in lower latitudes. So that’s a large scale event and it starts to put us in the range of the kind of climate shift that is being predicted by climate models today say for the next 100 years.
Looking to the past, not future
But paleontologists, like Bloch, don’t try to predict future climate change. They look to the past to try to understand the present.
“Because the Earth went through substantial climate change in the past – some of it very rapid and large scale – there’s a record in the rocks for exactly how animals and plants responded. And so we can go back as paleontologists and just reap the benefits of those experiments. We document that by collecting fossils and studying them. And then we can report them to the world with regards to how we should think about the reaction of plants and animals to the potential future climate change. With regards to how much we know about future climate change, that’s really a round for climate scientists and climate modelers,” he said.
Now, although the focus was on tiny horses 56 million years ago, the question still arises as to whether rising temperatures will mean smaller people in the future? Bloch says that’s possible. But there are a lot of factors involved. Right now, humans are getting bigger and that’s generally due to better nutrition. Humans could also adapt to rising temperatures by spending more time in air conditioned spaces.
There’s evidence today that temperatures and mammal size are linked.
“What you’re referring to is an observation that’s been coined Bergmann’s rule. And essentially¹⁰ what this rule says is that mammals of smaller size live in warmer environments and mammals of larger size live in cooler environments. And this has been documented in many different species of mammals,” said Bloch.
So maybe the lesson for future humans is to eat well and stay cool.
In the meantime, Bloch and his colleagues will continue to collect fossils in the Bighorn Basin. He says their future discoveries may be of interest to climate scientists.
Their latest findings can be found in the February 24th issue of Science magazine.

1 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

2 thermal   

adj.热的，由热造成的；保暖的

参考例句：

• They will build another thermal power station.他们要另外建一座热能发电站。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

3 primates   

primate的复数

参考例句：

• Primates are alert, inquisitive animals. 灵长目动物是机灵、好奇的动物。
• Consciousness or cerebration has been said to have emerged in the evolution of higher primates. 据说意识或思考在较高级灵长类的进化中已出现。

4 jaws   

n.口部；嘴

参考例句：

• The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
• The scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。

5 initially   

adv.最初，开始

参考例句：

• The ban was initially opposed by the US.这一禁令首先遭到美国的反对。
• Feathers initially developed from insect scales.羽毛最初由昆虫的翅瓣演化而来。

6 isotope   

n.同位素

参考例句：

• The isotope ratio is directly used for comparing oils or gases.同位素比率直接用于比较各种石油或天然气。
• How to apply a radio isotope?如何运用放射性同位素？

7 isotopes   

n.同位素；同位素( isotope的名词复数 )

参考例句：

• the many isotopes of carbon 碳的诸多同位素
• Tritium is one of the mildest radioactive isotopes. 氚是最和缓的放射性同位素之一。 来自《简明英汉词典》

8 interval   

n.间隔，间距；幕间休息，中场休息

参考例句：

• The interval between the two trees measures 40 feet.这两棵树的间隔是40英尺。
• There was a long interval before he anwsered the telephone.隔了好久他才回了电话。

9 latitudes   

纬度

参考例句：

• Latitudes are the lines that go from east to west. 纬线是从东到西的线。
• It was the brief Indian Summer of the high latitudes. 这是高纬度地方的那种短暂的晚秋。

10 essentially   

adv.本质上，实质上，基本上

参考例句：

• 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。