To the question of who came first, the chicken or the egg, science and the theory of evolution offer a clear answer: the egg. There is enough evidence to say that there were animals with the ability to hatch before the poultry we know today existed. Now, the enigma has moved to more diffuse terrain. Some geneticists are trying to find out how long life has had the ability to develop embryonic development.
A clue has just emerged thanks to a team of scientists from the University of Geneva (UNIGE). In his latest research on a primitive single-celled organism called Chromosphaera perkinsii, They discovered genetic instructions within it that are similar to those that allow embryonic formations in the eggs of birds and reptiles.
Organisms like C. perkinsii They have inhabited the Earth for more than 1 billion years. At that time the planet was very different, with an atmosphere composed of methane, ammonia and water vapor, and global temperatures of up to 50° C. For its part, records of the first animals date back to the Ediacaran period, almost 400 million years later, when the atmosphere was already full of oxygen and the temperature was less hostile. For the Geneva researchers, the results suggest that the instructions for forming embryonic patterns precede any identified animal.
In the fertilized eggs of chickens, the zygote travels through the oviduct, where various layers are added: first the white, then the membranes and finally the hard calcium shell. While the egg is forming, the zygote divides and differentiates to give rise to an embryo. The samples of Chromosphaera perkinsii revealed that once they reach their maximum size, they divide without growing any more. This process allows the generation of differentiated multicellular colonies, similar to the first stages of an embryo.
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