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Mammals can produce their own body heat and control their body temperatures.
哺乳动物可以产生自己的身体热量并控制自己的体温。
This process is known as endothermy or warm-bloodedness.
这个过程被称为温血动物的体温调节。
Scientists believe that it may be the reason why mammals likely rule almost every ecosystem.
科学家认为，这可能是哺乳动物统治几乎所有生态系统的原因。
Warm-blooded mammals are more active than cold-blooded animals.
温血哺乳动物比冷血动物更活跃。
They can live in different environments, from the frozen arctic to the boiling desert.
它们可以生活在不同的环境中，如冰冷的北极、炽热的沙漠。
And they reproduce faster.
而且它们的繁殖速度更快。
The soft tissues that would give information about warm- or cold-bloodedness are rarely preserved in fossils.
提供有关温血或冷血信息的软组织很少能被保存在化石中。
So, paleontologists, or experts in the study of fossils, do not know exactly when mammals developed and changed into warm-blooded creatures.
因此，古生物学家（即研究化石的专家）并不确切地知道哺乳动物是什么时候进化成温血动物的。
A group of scientists tried to answer that question in a study recently published in Nature.
一组科学家在最近发表在《自然》杂志上的一项研究中试图回答这个问题。
Ricardo Araújo is a paleontologist at the University of Lisbon.
里卡多·阿劳霍是里斯本大学的古生物学家。
Araújo and a group of researchers proposed that the shape and size of the inner ear structures called canals could be used to study body temperature.
阿劳霍和一组研究人员提出，可以根据被称为耳道的内耳结构的形状和大小来研究体温。
The movement of fluid through the ear canals helps the body to preserve balance and movement.
液体在耳道内流动有助于身体保持平衡和运动。
This fluid in cold-blooded animals is cooler and thicker, meaning wider canals are needed.
冷血动物体内的液体更冷、更稠，这意味着需要更宽的耳道。
Warm-blooded animals have less ear fluid and smaller canals.
温血动物耳朵里的液体较少，因此耳道较小。
The research team suggested that as body temperature increased and the animals became more active, the shape and size of ear canals changed to preserve balance and movement.
该研究小组认为，随着体温升高和动物变得更加活跃，为了保持平衡和运动，耳道的形状和大小会发生变化。
The researchers compared ear canals in 341 animals.
研究人员比较了341只动物的耳道。
They said the ear canals showed that warm-bloodedness, or endothermy, appeared around 233 million years ago, millions of years later than some previous estimates.
他们表示，耳道表明温血动物出现在大约2.33亿年前，比之前估计的数值晚了数百万年。
Araújo said, "Endothermy is a defining feature of mammals, including us humans.
阿劳霍说：“温血性是哺乳动物（包括我们人类在内）的一个典型特征。
Having a … high body temperature regulates all our actions and behaviors.”
高体温会调节我们所有的行动和行为。”
But the first creatures that showed warm-bloodedness are not officially considered to be mammals.
但是，最早表现出温血性的生物并不被官方认为是哺乳动物。
These ancient animals known as mammaliamorph synapsids had traits linked with mammals.
这些被称为“mammaliamorph synapsids”的古老动物具有与哺乳动物相关的特征。
The first true mammals, the researchers said, appeared roughly 30 million years later.
研究人员表示，第一个真正的哺乳动物出现在大约3000万年后。
Ken Angielczyk of the Field Museum in Chicago is a co-leader of the study.
芝加哥菲尔德博物馆的肯·安吉尔奇克是这项研究的共同负责人。
He said, "Given how central endothermy is to so many aspects of the body plan, physiology and lifestyle of modern mammals, when it evolved in our ancient ancestors has been a really important unsolved question…”
他说：“鉴于温血性对现代哺乳动物的身体结构、生理机能和生活方式等诸多方面的重要性，我们远古祖先何时进化为温血动物一直是一个非常重要的悬而未决的问题……”
Endothermy evolved at a time when important elements of the mammal body plan were falling into place, including changes to the backbone, breathing system, and hearing system.
哺乳动物在其身体的重要组成部分（包括脊骨、呼吸系统和听力系统的变化）已经形成的时候进化成了温血动物。
Having warm-bloodedness also helped mammals at an important evolutionary moment when dinosaurs and flying reptiles first appeared on Earth.
在恐龙和会飞的爬行动物首次出现在地球上的重要进化时刻，拥有温血性对哺乳动物也有利。
And mammals took over after the dinosaur mass extinction event 66 million years ago.
哺乳动物在6600万年前恐龙大灭绝事件后取代了恐龙。
Among today's animals, mammals and birds are warm-blooded.
在如今的动物中，哺乳动物和鸟类是温血动物。
"It is maybe too far-fetched, but interesting, to think that the onset of endothermy in our ancestors may have ultimately led to the construction of the Giza pyramids or the development of the smartphone," Araújo said.
阿劳霍说：“认为我们祖先的温血性可能最终导致了吉萨金字塔群的建造或智能手机的发展可能太牵强了，但却很有趣。”
"If our ancestors would have not become independent of environmental temperatures, these human achievements would probably not be possible."
“如果我们的祖先没有独立于环境温度，人类就可能不会实现这些成就。”
I’m John Russell.
约翰·拉塞尔为您播报。
译文为可可英语翻译，未经授权请勿转载！
