If we trace our evolutionary lineage far enough into the past, humans and all other vertebrates living on land will stumble upon primitive fish like great-grandparents. Although there are millions of years of evolution between our gill-bearing ancestors and us, a team of scientists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and their collaborators have found evidence confirming that the human ear medium evolved from the gills of primitive fish.
It is likely that the character of The Sailor -Kevin Costner- from the 1995 film Water World in which climate change causes not only changes in the planet, but also in human beings, comes to mind; this character has gills behind his ears that allow him to breathe underwater and swim faster; maybe this position wasn’t so wrong after all…
The gills became part of the ear of modern vertebrates
Over the past 20 years, the researchers successively found a 438-million-year-old Shuyu 3D braincase fossil (considered as important a missing link as Archeopteryx ) and the first perfectly preserved 419-million-year-old galáespid fossil with gill filaments in the first branchial chamber The fossils were found in Changxing, Zhejiang Province, and Qujing, Yunnan Province, respectively.
They analyzed the 3D skulls of these fish, and found evidence that our ears evolved over millennia from their gills. Thus, embryonic and fossil evidence proves that the human middle ear evolved from the blowhole of fish.
“SRXTM provides a means of non-destructive investigation of the internal structures of organisms with high spatial resolution and has been applied to address a number of paleontological problems that would be undesirable by destructive means. This approach [was] successfully applied to characterize the cranial anatomy of Shuyu ,” the researchers said.
Reconstruction of Shuyu’s braincase reveals the presence of a spiracular gill
“These fossils provided the first anatomical and fossil evidence of a vertebrate spiracle that originated in the gills of fish,” explains Gai Zhikun, leader of the work published in the journal Frontiers in Ecology and Evolution. “Many important structures of humans date back to our fish ancestors, such as teeth, jaws, middle ear, etc. The main task of paleontologists is to find the important missing links in the evolutionary chain from fish to humans “.
The bones of the middle ear convert the vibrations of the eardrum into more powerful pressure waves that allow us to hear even very small disturbances over a wide range of frequencies. And they evolved from something else: fish gills.
“Our finding ties the whole story of the spiracular slit together, bringing together recent discoveries from the gill sacs of fossil jawless vertebrates, through the spiracles of early jawed vertebrates, to the middle ear of early tetrapods, which tells this remarkable story. evolutionary history,” concludes Per E. Ahlberg of Uppsala University and academician at the Royal Swedish Academy of Sciences.
So it seems that the next time you put on your favorite song, you might be thinking that you owe it to ancient primitive fish for this privilege of being able to listen to these fabulous sounds.
Referencia: Zhikun Gai et al, The Evolution of the Spiracular Region From Jawless Fishes to Tetrapods, Frontiers in Ecology and Evolution (2022). DOI: 10.3389/fevo.2022.887172
