Scientists from the University of Copenhagen (Denmark) have completed the genome sequencing of the platypus, a unique animal and endemic to Australia. Together with the viper, it belongs to the oviparous - a separate group of mammals that lay eggs, but at the same time feed their young with milk. The study of the genes of the platypus finally made it possible to explain this and many other mysteries of this extremely unusual creature.
According to the updated theory, oviparous, marsupial and placental mammals had a common ancestor 187 million years ago, after which they divided into three branches, each of which evolved in its own direction. The platypus was "lucky" to occupy a separate niche in the nature of ancient Australia, at the junction of water and land. Therefore, he practically did not change since then, thanks to which scientists were surprised to find in his genome the genes lost in other groups. Namely, the genes of birds and reptiles, despite the fact that the platypus itself is a mammal.
Modern birds have three genes that are responsible for creating a nutritious protein mass in the egg, which serves as food for future chicks. A person does not have these genes at all, and the platypus has only one of them. At the same time, he has genes for the formation of casein, which, although they differ from cow or human, but thanks to them, almost the same milk is created. Therefore, the platypus lays eggs, but its cubs do not have enough food, and they have to additionally feed them with milk. However, the animal does not have nipples or their analogue - milk comes out directly through the skin.
Another example of evolutionary miracles is the ten sex chromosomes, 5X and 5Y, enclosed in a ring. Why such redundancy, when one pair of XY is enough for a person, scientists cannot say. Even in the genome of the platypus, four genes responsible for the formation of teeth are missing, so it has a beak instead. And the poisonous spurs on the hind legs are a feature of the immune system that helps to produce special protective proteins for toxins. Interestingly, the closest relative of the platypus, the echidna, has long lost this ability.