Scientists study the inner ear to determine the origin of mammals

Mammals can generate their own body heat and control their body temperature. This process is known as endothermic or warm-blooded.

Scientists believe that may be the reason why mammals tend to dominate almost everything ecosystem. Warm-blooded mammals are more active than cold-blooded animals. They can live in different environments, from frozen poles to boiling deserts. And they breed faster.

Soft tissue that will provide information about being warm or cold blooded is rare preserved in fossil. So paleontologists, or experts in the study of fossils, don’t know exactly when mammals evolved and turned into warm-blooded creatures.

A group of scientists tried to answer that question in a study recently published in Natural.

Ricardo Araújo is a paleontologist at the University of Lisbon. Araújo and a group of researchers proposed that the shape and size of inner ear structures called canals could be used to study body temperature.

The movement of fluid through the ear canal helps the body maintain balance and movement. The fluid in these cold-blooded animals is colder and thicker, meaning wider canals are needed. Warm-blooded animals have less ear fluid and smaller canals.

The research team suggests that as body temperature increases and animals become more active, the shape and size of the ear canal changes to maintain balance and movement.

The researchers compared the ear canals in 341 animals. They say the ear canal suggests that warm blooded, or endothermic, appeared about 233 million years ago, millions of years later than previously thought.

Araújo said, “Endothermy is the definition feature mammals, including us humans. Having … high body temperature arrange all of our actions and behavior.”

But the first creatures to show warm bloodedness are not officially considered mammals. This ancient animal known as a morphological mammal synapsid has a traits associated with mammals. The first true mammals, the researchers say, appeared about 30 million years later.

The importance of being warm-blooded

Ken Angielczyk of the Field Museum in Chicago is one of the leaders of the study. He said, “Given how important endotherms are to many people aspect from the body plan, physiology and lifestyle of modern mammals, at that time evolve our ancestry has become an important unsolved question…”

Endothermy evolved at a time when important elements of the mammalian body plan came into play, including changes to the spine, respiratory system, and auditory system.

Having warm blood also helped mammals at a crucial 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.

“Might also making it upbut interesting, to think that endothermic beginnings in our ancestors might have ultimately led to the construction of the Giza pyramids or the development of smartphones,” Araújo said.

“If our ancestors had not been independent of environmental temperatures, this human achievement would probably not have been possible.”

I’m John Russell.

John Russell adapted this story for VOA Learning English based on Nature, Scientific American, and Reuters news reports.

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Words in This Story

ecosystem – n. everything that exists in a certain environment

conserve – v. to keep (something) in its original state or in good condition

fossil – n. something (such as a leaf, skeleton, or footprint) that comes from a plant or animal that lived in ancient times and that you can see in some rocks

feature – n. interesting or important parts, qualities, abilities, etc.

arrange – v to set or adjust the amount, degree, or degree of (something)

nature – n. the quality that makes one person or thing different from another

aspect – n. part of something

develop – v often change or evolve slowly into a better, more complex, or more advanced state: evolve through the process of evolution

making it up – adj. can’t happen or come true

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