An Australian paleontologist has made a major evolutionary discovery about how four-legged animals first developed the ability to breathe air after observations of African fish.
Flinders University palaeontologist John Long has found evidence that four-limbed animals, including people, first developed the ability to breathe air as ancient fish in water.
As part of the study, a team based at The Scripps Research Institute in the US observed species of Polypterus, the most primitive living fish on the planet, and measured the amount of oxygen it was taking in.
People had suspected the African fish breathed air though their mouths like lungfish, but the researchers found it was through tiny little holes called spiracles in the top of the head.
Professor Long said the discovery, published in the journal Nature Communications, solved a 100-year mystery surrounding the Polypterus.
It has significant implications in evolutionary understanding because it almost certainly means a raft of fossils with similar holes on their heads also breathed that way.
This includes the ancient Gogonasus, which belonged to a group of fish widely regarded as the ancestors from whom the first land animals evolved.
"Until now we've only had theories about the origins of breathing in the evolution of fish to land animals - some early 19th-century scientists had these wacky ideas that fish just jumped onto the land and started gasping for breath and developing limbs," Prof Long said.
"This is important because it shows that breathing first started in our lineage through these fish breathing through their heads, not like we would have guessed, like lungfish."
He said a byproduct of the research breakthrough was also finding the origin of hearing in terrestrial animals.
The spiracles eventually became the hearing canal, he said.
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