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a U.S.-China research team led by Dr. Wang Shuo of the School of Life Sciences at Capital Normal University made a major breakthrough in the evolution of bird slugs, the results of which were published online September 26 in the journal
. This is another breakthrough in this field of research following the team's report in The Current Biology in January 2017 on the gradual loss of teeth in the development of individuals.
is an important organ that evolved in many animal-footed dinosaurs, including birds. Early birds had teeth, while progressive birds and all living birds had gills. In the past, there have been more in-depth studies on the development process of the current bird's beak, but the causes and mechanisms of tooth loss of birds have been widely debated. The conventional view is that tooth loss helps to reduce the weight of birds and enhance their ability to fly, and there is also the view that simple genetic mutations cause tooth loss in birds. In January 2017, Wang Shuo's team reported on the gradual loss of teeth found in an animal-footed dinosaur, the unscathed quagmire dragon, during individual development, which brought a new dawn to the mechanism of tooth loss in birds. In subsequent studies, the team found that the gradual loss of teeth during individual development was also present in egg-stealing dragons and keegan birds, and that tooth loss was increasingly early in the evolution of dinosaurs to birds -- phenomena that suggest that hetero-developmental degeneration of teeth is the direct cause of tooth loss in birds.
loss of teeth is bound to be accompanied by changes in the feeding organs. The team found an inevitable link between tooth loss and the development of gills through a characteristic correlation analysis based on big data. Previous studies have shown that bone-form protein BMP not only controls tooth development, but also participates in the process of gills. The team confirmed through developmental biology experiments that this increase in signaling path expression can also promote the growth of gills while causing tooth development disruption -- a result that for the first time sheds light on the possible mechanisms of dental heterogeneity. New research suggests that genetic mutations are not the real cause of tooth loss in birds. Previous relevant molecular genetic studies have been based mainly on living birds, and natural selection of birds after the emergence of the role of the relevant genes in the teeth gradually decreased, resulting in the mutation and loss of these genes. Therefore, the mutation of the tooth development gene of birds should be an event in the later stages of bird evolution, not a direct cause of tooth loss in birds.
, who led the study, said:
A most importantly, this phenomenon is not only present in dinosaur-bird branches, but also in dozens of vertebrates. This shows that the loss of teeth is a commonly used 'means' of vertebrate 'lost teeth', which not only subverts our understanding of the evolutionary history of birds, but also has far-reaching significance for understanding the pattern of tooth evolution in vertebrates."Thanth time-varying developmental loss of teeth is common in vertebrates in different categories
the study was jointly funded by the National Natural Science Foundation of China, the National Natural Science Foundation of the United States, the National Key Laboratory of Modern Paleontology and Strataology of the Chinese Academy of Sciences, and the Youth Research and Innovation Team project of Capital Normal University. (Source: Science.com)