Scientists Study Inner Ear to Determine Beginnings of Mammals
2022-08-01
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1Mammals can produce their own body heat and control their body temperatures.
2This process is known as endothermy or warm-bloodedness.
3Scientists believe that it may be the reason why mammals likely rule almost every ecosystem.
4 Warm-blooded mammals are more active than cold-blooded animals.
5They can live in different environments, from the frozen arctic to the boiling desert.
6And they reproduce faster.
7The soft tissues that would give information about warm- or cold-bloodedness are rarely preserved in fossils.
8So, paleontologists, or experts in the study of fossils, do not know exactly when mammals developed and changed into warm-blooded creatures.
9A group of scientists tried to answer that question in a study recently published in Nature.
10Ricardo Araújo is a paleontologist at the University of Lisbon.
11Araújo 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.
12The movement of fluid through the ear canals helps the body to preserve balance and movement.
13This fluid in cold-blooded animals is cooler and thicker, meaning wider canals are needed.
14Warm-blooded animals have less ear fluid and smaller canals.
15The research team suggested that as body temperature increased and the animals became more active,
16the shape and size of ear canals changed to preserve balance and movement.
17The researchers compared ear canals in 341 animals.
18They said the ear canals showed that warm-bloodedness, or endothermy, appeared around 233 million years ago, millions of years later than some previous estimates.
19Araújo said, "Endothermy is a defining feature of mammals, including us humans.
20Having a ... high body temperature regulates all our actions and behaviors."
21But the first creatures that showed warm-bloodedness are not officially considered to be mammals.
22These ancient animals known as mammaliamorph synapsids had traits linked with mammals.
23The first true mammals, the researchers said, appeared roughly 30 million years later.
24Ken Angielczyk of the Field Museum in Chicago is a co-leader of the study.
25He 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..."
26Endothermy 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.
27Having warm-bloodedness also helped mammals at an important evolutionary moment when dinosaurs and flying reptiles first appeared on Earth.
28And mammals took over after the dinosaur mass extinction event 66 million years ago.
29Among today's animals, mammals and birds are warm-blooded.
30"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.
31"If our ancestors would have not become independent of environmental temperatures, these human achievements would probably not be possible."
32I'm John Russell.
1Mammals can produce their own body heat and control their body temperatures. This process is known as endothermy or warm-bloodedness. 2Scientists believe that it may be the reason why mammals likely rule almost every ecosystem. Warm-blooded mammals are more active than cold-blooded animals. They can live in different environments, from the frozen arctic to the boiling desert. And they reproduce faster. 3The soft tissues that would give information about warm- or cold-bloodedness are rarely preserved in fossils. So, paleontologists, or experts in the study of fossils, do not know exactly when mammals developed and changed into warm-blooded creatures. 4A group of scientists tried to answer that question in a study recently published in Nature. 5Ricardo Araújo is a paleontologist at the University of Lisbon. 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. 6The movement of fluid through the ear canals helps the body to preserve balance and movement. This fluid in cold-blooded animals is cooler and thicker, meaning wider canals are needed. Warm-blooded animals have less ear fluid and smaller canals. 7The 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. 8The researchers compared ear canals in 341 animals. 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. 9Araújo said, "Endothermy is a defining feature of mammals, including us humans. Having a ... high body temperature regulates all our actions and behaviors." 10But the first creatures that showed warm-bloodedness are not officially considered to be mammals. These ancient animals known as mammaliamorph synapsids had traits linked with mammals. The first true mammals, the researchers said, appeared roughly 30 million years later. 11Importance of being warm-blooded 12Ken Angielczyk of the Field Museum in Chicago is a co-leader of the study. 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..." 13Endothermy 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. 14Having warm-bloodedness also helped mammals at an important evolutionary moment when dinosaurs and flying reptiles first appeared on Earth. And mammals took over after the dinosaur mass extinction event 66 million years ago. Among today's animals, mammals and birds are warm-blooded. 15"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. 16"If our ancestors would have not become independent of environmental temperatures, these human achievements would probably not be possible." 17I'm John Russell. 18John Russell adapted this story for VOA Learning English based on Nature, Scientific American and Reuters news reports. 19________________________________________________________________________ 20Words in This Story 21ecosystem - n. everything that exists in a particular environment 22preserve - v. to keep (something) in its original state or in good condition 23fossil - n. something (such as a leaf, skeleton, or footprint) that is from a plant or animal which lived in ancient times and that you can see in some rocks 24feature - n. an interesting or important part, quality, ability, etc. 25regulate - v. to set or adjust the amount, degree, or rate of (something) 26trait - n. a quality that makes one person or thing different from another 27aspect - n. a part of something 28evolve - v. to change or develop slowly often into a better, more complex, or more advanced state : to develop by a process of evolution 29far-fetched - adj. not likely to happen or be true