Hair, feathers and scales have a common ancestor.
A group of scientists from Switzerland was able to prove that hair, scales and feathers are homologous and descended from a common ancestor - reptiles. The theoretical background and results of the experiments were described in detail in the pages of the journal Science Advances and briefly in a press release submitted on behalf of the University of Geneva. Today we will talk about what served as proof of such a bold statement and what conclusion for further research can do the work done.
Most mammals, birds, and reptiles are easily recognizable by hair, feathers, and scales, respectively. However, the lack of transitional forms in fossil forms between scales and hairs and significant differences in their morphogenesis and protein composition have led to disputes over their potential common ancestry that has been going on for many decades.
Scientists have long known that mammals' hair and feathers of birds develop from the primitive structure of the placode - a kind of thickening of the epidermis with columnar cells, reducing their proliferation rate and producing specific genes. This observation, again, drew a line between supporters of a single ancestor in birds and mammals and opponents of such an assumption, claiming that both are completely different species with different pedigrees. At the same time, the supporters of the latest version somehow turned a blind eye to the fact that it compels us to accept the fact that the two completely different, according to their claims, “invented” the placode independently of each other.
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In 2015, scientists from Yale University (USA) published an article demonstrating that scales, hair and feathers at an early stage of development have a common molecular signature. The published results again added fuel to the long-standing controversy between the two schools of evolutionists. Adherents of one of which continued to defend the vitality of the hypothesis that identical molecular signatures indicate a common evolutionary origin of skin appendages, and supporters of the other that for the development of different skin appendages during evolution at some stage the same genes were reused.
Points above "And"
The latest work of biologists Nicolas Di-PoĂŻ and Michel C. Milinkovitch from the Department of Genetics and Evolution at the University of Geneva (UNIGE) and the Swiss Institute of Bioinformatics (SIB) has put an end to this long-standing discussion. Scientists have shown that reptile scales developed from placodes with anatomical and molecular signatures similar to those of placodes of birds and mammals in the early stages of development.
In the course of the research, the morphological and molecular characteristics of the skin during the embryonic development of crocodiles, snakes and lizards were analyzed. “Our research not only provides new molecular data that complements the work of the American team, but also reveals key micro-anatomical facts,” explains Michel Milinkovic. “Indeed, we have identified in the reptile new molecular signatures identical to those observed in the development of hairs and feathers, as well as the presence of an anatomical placode, similar to the placode of mammals and birds. This indicates that the three types of skin appendages are homologous: scales - in reptiles, feathers - in birds, and hair - in mammals, despite their very different final forms, evolved from their common ancestor, reptiles. ”
Key gene development of skin appendages
At the next stage of the study, the authors studied bearded dragons, represented by three forms. The first form is the usual wild species, the second form is characterized by smaller sizes, and the third, in turn, has mutated in two directions with many different defects, including the complete absence of scales. Comparing the genomes of the three considered subspecies of bearded dragons, scientists were able to identify the defective gene, which resulted in a known variety of forms. This is ectodisplasin-A (EDA), the mutation of which ultimately led to the release of one of the forms of bearded dragons from scales.
"We determined that the peculiar appearance of these naked lizards is due to the disruption of Ectodysplasin-A, a gene whose mutation in humans and mice is known to generate significant abnormalities in the development of teeth, glands, nails and hair," explained Michel Milinkovic. Based on research and comparative analysis, Swiss scientists have shown that in lizards with a mutated EDA gene, the placode structure is disrupted, just as in mammals or birds affected by similar mutations in the same gene, my own hair or feathers cannot develop from placodes. These data all together coherently indicate the common origin of scales, feathers and hair.
Having received such convincing evidence of the unity of origin, the scientists intend to continue research, identify and describe the mechanisms that underlie the development of a specific form of skin appendages. This, in turn, will provide an answer to another crucial question: how did the most ancient scaly skin cover give rise to the existing morphological diversity of scales, feathers and hair. “These studies, we hope, will complement our understanding of the physical and molecular mechanisms that give rise to the complexity and diversity of life in the course of evolution,” Malinkovich concluded.
It is interesting that earlier, studying the chameleon's ability to change its color, Michel Malinkovich was able to explain the nature of this amazing phenomenon by actively restructuring the spatial structure of skin nanocrystals.
The full text of the scientific publication can be found here.
Science Advances 24 Jun 2016:
Vol. 2, no. 6, e1600708
DOI: 10.1126 / sciadv.1600708
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Most mammals, birds, and reptiles are easily recognizable by hair, feathers, and scales, respectively. However, the lack of transitional forms in fossil forms between scales and hairs and significant differences in their morphogenesis and protein composition have led to disputes over their potential common ancestry that has been going on for many decades.
Scientists have long known that mammals' hair and feathers of birds develop from the primitive structure of the placode - a kind of thickening of the epidermis with columnar cells, reducing their proliferation rate and producing specific genes. This observation, again, drew a line between supporters of a single ancestor in birds and mammals and opponents of such an assumption, claiming that both are completely different species with different pedigrees. At the same time, the supporters of the latest version somehow turned a blind eye to the fact that it compels us to accept the fact that the two completely different, according to their claims, “invented” the placode independently of each other.
')
In 2015, scientists from Yale University (USA) published an article demonstrating that scales, hair and feathers at an early stage of development have a common molecular signature. The published results again added fuel to the long-standing controversy between the two schools of evolutionists. Adherents of one of which continued to defend the vitality of the hypothesis that identical molecular signatures indicate a common evolutionary origin of skin appendages, and supporters of the other that for the development of different skin appendages during evolution at some stage the same genes were reused.
Points above "And"
The latest work of biologists Nicolas Di-PoĂŻ and Michel C. Milinkovitch from the Department of Genetics and Evolution at the University of Geneva (UNIGE) and the Swiss Institute of Bioinformatics (SIB) has put an end to this long-standing discussion. Scientists have shown that reptile scales developed from placodes with anatomical and molecular signatures similar to those of placodes of birds and mammals in the early stages of development.
In the course of the research, the morphological and molecular characteristics of the skin during the embryonic development of crocodiles, snakes and lizards were analyzed. “Our research not only provides new molecular data that complements the work of the American team, but also reveals key micro-anatomical facts,” explains Michel Milinkovic. “Indeed, we have identified in the reptile new molecular signatures identical to those observed in the development of hairs and feathers, as well as the presence of an anatomical placode, similar to the placode of mammals and birds. This indicates that the three types of skin appendages are homologous: scales - in reptiles, feathers - in birds, and hair - in mammals, despite their very different final forms, evolved from their common ancestor, reptiles. ”
Key gene development of skin appendages
At the next stage of the study, the authors studied bearded dragons, represented by three forms. The first form is the usual wild species, the second form is characterized by smaller sizes, and the third, in turn, has mutated in two directions with many different defects, including the complete absence of scales. Comparing the genomes of the three considered subspecies of bearded dragons, scientists were able to identify the defective gene, which resulted in a known variety of forms. This is ectodisplasin-A (EDA), the mutation of which ultimately led to the release of one of the forms of bearded dragons from scales.
"We determined that the peculiar appearance of these naked lizards is due to the disruption of Ectodysplasin-A, a gene whose mutation in humans and mice is known to generate significant abnormalities in the development of teeth, glands, nails and hair," explained Michel Milinkovic. Based on research and comparative analysis, Swiss scientists have shown that in lizards with a mutated EDA gene, the placode structure is disrupted, just as in mammals or birds affected by similar mutations in the same gene, my own hair or feathers cannot develop from placodes. These data all together coherently indicate the common origin of scales, feathers and hair.
Having received such convincing evidence of the unity of origin, the scientists intend to continue research, identify and describe the mechanisms that underlie the development of a specific form of skin appendages. This, in turn, will provide an answer to another crucial question: how did the most ancient scaly skin cover give rise to the existing morphological diversity of scales, feathers and hair. “These studies, we hope, will complement our understanding of the physical and molecular mechanisms that give rise to the complexity and diversity of life in the course of evolution,” Malinkovich concluded.
It is interesting that earlier, studying the chameleon's ability to change its color, Michel Malinkovich was able to explain the nature of this amazing phenomenon by actively restructuring the spatial structure of skin nanocrystals.
The full text of the scientific publication can be found here.
Science Advances 24 Jun 2016:
Vol. 2, no. 6, e1600708
DOI: 10.1126 / sciadv.1600708
That's all with you was Dronk.Ru. Do not forget to return money for purchases in China and subscribe to our blog , there will be many more interesting things.
We recommend:
- Save up to 8% on every purchase on AliExpress and other online stores in China
- Why do online stores give money for purchases?
- Return your money - Choose a cashback service for Aliexpress
- The history of the development of Dronk.ru - from choosing quadcopters to returning money for purchases on AliExpress and not only
- The best cashback service or 5 main criteria for evaluating cashback service
Source: https://habr.com/ru/post/395759/
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