Scientists have found out, how did the teeth of the first human ancestors

© RIA Novosti / Anton to Danilovmarat fotoreceptori in the world. Coconut islandScientists have found out, how did the teeth of the first human ancestors© RIA Novosti / Anton to Danilovmarat the image Bank

Genetics has found new evidence that the primitive teeth are the most distant human ancestors could be the result of mutations in genes associated with the formation of scales in fish, according to a paper published in the journal PNAS.

«The scales of modern fish does not look like a skin of their ancestors. He was more similar in structure to teeth, and traces of it remained only in some of the ancient inhabitants of the seas of the Earth, such as sharks and rays. If you hold the skin of a shark a hand, you’ll know how hard it is for many skin teeth. No wonder in ancient times it was used as sandpaper,» says Andrew Gillies (Andrew Gillis) from the University of Cambridge (UK).

The first fish appeared on Earth about 500 million years ago, were generally similar to their modern descendants, with the exception of two features of the anatomy – they had no true jaws or teeth. Today scientists believe, jaws appeared in primitive fish and much later, 410-380 million years ago, resulting in the transformation of one of the Gill arches into a new «grasp» the device.

How exactly has any teeth, it is not clear, and scientists are fierce disputes about what part of the body of ancient fish could spawn, and whether they arose simultaneously with the jaws or came much later. A small number of fossils from the Devonian period, known today, allows for a similar debate almost indefinitely, as «iron» arguments in favor of this or that theory yet.

Gillis and his colleagues tried to find the answer to this question is not in the ancient past of the Earth, and in her present, watching as the body is created by echinoid Stingray (Leucoraja erinacea), and how there are «blanks» of his future teeth and scales.

Through this experiment, scientists were guided by a simple philosophy – if the real skin and teeth rays have common «roots», then they should be formed from the same type of embryonic cells. If not, then they will arise in different parts of the embryo, which indicates that the teeth have emerged some other way.

To reveal the mystery, the scientists introduced into the cells of the embryo, a special set of fluorescent molecules that adhere to fats and proteins in the walls of cells, allowing them to keep track of where were their descendants and how they have evolved with the growth of fry. Additionally, biologists observed the FoxD3 gene activity controlling the growth of cells-progenitors of the teeth.

These observations showed that the teeth and scales of the slope formed from the same source – the so-called neural crest, a specialized tissue of the embryo, the future surrounding the brain and spinal cord. Cells of the neural crest, as the scientists explain, are highly mobile and they can penetrate virtually all regions of the embryo as its development.

«Neural crest cells play a key role in the development of teeth in mammals. Our experiments indicate deep evolutionary link between primitive ancient fish scales and teeth of modern animals and people,» concludes geneticist.