Researchers have discovered a 380-million-year-old heart preserved inside a fossilized prehistoric fish.
They say the specimen captures a key moment in the evolution of the blood-pumping organ found in all spinal animals, including humans.
The heart belonged to a fish known as Gogo, now extinct.
The discovery described as “jaw-dropping”, published in the journal Science, was made in Western Australia.
The lead scientist involved, Professor Kate Trinajstic of Curtin University in Perth, told BBC News about the moment she and her colleagues realized they had made the biggest discovery of their lives.
“We were around the computer and we recognized that we had a heart and we practically couldn’t believe it! It was incredibly emotional,” she said.
Typically, it’s the bones and not the soft tissue that are turned into fossils — but at this site in the Kimberley, known as the Gogo rock formation — minerals have preserved many of the fish’s internal organs, including the liver, stomach, intestines and heart.
“This is a pivotal moment in our own evolution,” said Professor Trinajstic.
“This shows the body plan that we evolved very early on, and we see that for the first time in these fossils.”
His colleague Professor John Long of Flinders University in Adelaide described the discovery as “a mind-boggling and jaw-dropping discovery”.
“We didn’t know anything about the soft organs of such ancient animals, until now,” he said.
The Gogo fish is the first of a class of prehistoric fish called placoderms. They were the first fish to have jaws and teeth. Before them, fish were no more than 30 cm, but placoderms could grow up to nine meters in length.
Placoderms were the dominant life form on the planet for 60 million years, existing over 100 million years before the first dinosaurs existed.
Fossil scans of the Gogo fish showed that its heart was more complex than expected for these early fish. It had two chambers, one on top of the other, with a structure similar to the human heart.
The researchers suggest that this made the animal’s heart more efficient and was the critical step that transformed it from a slow fish into a fast predator.
“This was the way they could increase the chances of becoming voracious predators,” said Professor Long.
The other important observation was that the heart was much further forward in the body than in more primitive fish.
This position is thought to have been associated with the development of the Gogo fish’s neck and made room for the development of lungs further down the evolutionary line.
Zerina Johanson of the Natural History Museum in London, a world leader in placoderms and not part of Professor Trinajstic’s team, described the research as an “extremely important discovery” that helps explain why the human body is the way it is. .
“Many of the things you see we still have in our own bodies; jaws and teeth, for example. There are many things going on in these placoderms that we see evolving for ourselves today, such as the neck, the shape and arrangement of the heart and its position in the body. body”.
The discovery is an important step in the evolution of life on Earth, according to Martin Brazeau, a placoderm expert at Imperial College London, who is also independent of the Australian research team.
“It’s really exciting to see this result,” he told BBC News.
“The fish that my colleagues and I are studying are part of our evolution. This is part of the evolution of humans and other animals that live on land and of fish that live in the sea today.”
This text was originally published here.
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