This century-old mystery that has plagued scientists now has an answer-a few days ago, an international joint research team led by researcher Gai Zhikun from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences recently published in the international academic journal “Frontiers of Ecology and Evolution” New research on the origin of vertebrate blowholes reveals for the first time that the human middle ear was once the gills used by fish to Technology breathe.
Gai Zhikun introduced that since 2002, the research team has carried out field work in the Silurian strata of Changxing, Zhejiang, and found one of the most primitive true armored fish fossils here, and named it Shuyu. “These fossils are precious specimens preserved with three-dimensional cartilage skulls, and they are all very small, only the size of our fingernails. We carried out three-dimensional non-destructive scanning and three-dimensional virtual restoration, which lasted for 5 years. In total, the three-dimensional reconstructions of seven fossil skulls of Drosophila have been completed, and almost all brain regions, sensory organs, and nerves and blood vessels in the skull have been reconstructed.”
The research team conducted in-depth research on the three-dimensional virtual model of the brain and skull of Shuyu fish, and combined with the first new material of broad turtle that completely preserved the gill silk print in the first gill sac, which was discovered in Qujing, Yunnan, and finally completed the process from gill to spray. The evolutionary puzzle of the water hole to the middle ear – The research team established the evolutionary sequence of the water blow hole from the gills of the jawless to the human middle ear.
Gai Zhikun introduced that this sequence shows that with the splitting of the paired nasal sacs of the armored fish, an abnormally developed middorsal foramen (single nostril) developed in front of the head armor to act as the main respiratory organ for inhaling water, so the jaw arch The lingual-maxillary sac between the lingual arch and the lingual arch developed into a complete gill sac for the first time. Like the five normal gill sacs behind, the gill sac has complete anterior and posterior half-gills. The half-gills have gill filaments and are the main place for gas exchange. . Since then, the jaws have successfully evolved double nostrils, but the double nostrils do not communicate with the oral cavity, and have no breathing function, only olfactory function. However, the breathing needs of fish have not decreased, so the first-gill sac behind the eyes (lingual-maxillary sac) has been transformed into a water jet hole, which has become the main organ for inhaling water. “This was already present in the most primitive jawed placodes, and we speculate that the blowhole probably originated at the same time as the jaws and double nostrils in the jawed companion.”
“All of this evidence suggests that early teleost fishes had the ability to breathe air from blowholes as a new way of breathing, which is likely a part of the way fish leave the water and land on land to breathe air,” said Gai Zhikun. This pre-adaptation feature. However, as the nose evolved into the main respiratory organ, the spout lost its respiratory advantage, and after modification, it gradually evolved into the cavity of our middle ear, the tympanic chamber, and the hyoid and jaw bone and its joints. The square and articular bones also gradually degenerate and become smaller, eventually entering our middle ear and evolving into the three ossicles of our middle ear, which were renamed the stapes, malleus and incus, responsible for transmitting sound to the brain , ultimately giving us a sensitive hearing.”
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