Scientists examine the inner ear to determine the beginnings of mammals

Mammals can produce their own body heat and control their body temperature. This process is called endothermy or warm-blooded animals.

Scientists think this could be why mammals probably rule almost everyone ecosystem. Warm-blooded animals are more active than cold-blooded animals. They can live in different environments, from the frozen arctic to the boiling desert. And they multiply faster.

The soft tissues that would reveal warm-blooded or cold-blooded are rare preserved in fossils. So paleontologists or experts in the study of fossils do not know exactly when mammals evolved and turned into warm-blooded creatures.

A group of scientists attempted to answer this question in a recently published study Nature.

Ricardo Araújo is a paleontologist at the University of Lisbon. Araújo and a group of researchers suggested 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 canals helps the body maintain balance and movement. This fluid in cold-blooded animals is cooler and thicker, meaning wider channels are needed. Warm-blooded animals have less ear fluid and smaller canals.

The research team suggested that as the animals’ body temperature increased and the animals became more active, the shape and size of the ear canals changed to help maintain balance and movement.

The researchers compared the ear canals of 341 animals. They said the ear canals showed warm-blooded animals, or endotherms, appeared around 233 million years ago, millions of years later than some previous estimates.

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

But the first creatures to show warm-blooded animals are not officially considered mammals. Known as mammals, these ancient animals had synapsids Trains associated with mammals. The first true mammals, the researchers said, appeared about 30 million years later.

Importance of being warm-blooded

Ken Angielczyk of the Field Museum in Chicago is co-leading the study. He said: “Considering how central endothermy is to so many aspects of the body plan, physiology, and lifestyle of modern mammals, if it developed among our ancient ancestors was a really important unsolved question…”

Endothermy developed at a time when important elements of the mammalian body plan were coming into place, including changes to the spine, respiratory system, and auditory system.

Being warm-blooded also helped mammals at a key evolutionary moment when dinosaurs and flying reptiles first appeared on Earth. And mammals took over after the mass extinction of dinosaurs 66 million years ago. Among today’s animals, mammals and birds are warm-blooded.

“Maybe it is far-fetchedbut 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.

“If our ancestors hadn’t become independent of ambient temperatures, these human achievements probably wouldn’t have been possible.”

I’m John Russell.

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

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words in this story

ecosystem – n. everything that exists in a specific environment

maintain – v. keep (something) in its original condition or in good condition

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

special feature – n. an interesting or important part, quality, ability, etc.

regulate – v. to set or adjust the amount, degree, or rate of (something).

feature – n. a quality that distinguishes one person or thing from another

aspect – n. a part of something

develop – v. slowly changing or evolving, often into a better, more complex, or more advanced state: evolving through an evolutionary process

far-fetched – adj. probably not going to happen or be true