Look at the platypus. You can almost hear how David Attenborough’s soothing voice describes a being so peculiar, the mystery of how it originated has caused too many scientists headaches.
Platypuses can just as well be strange life forms on earth. They lay eggs. They sweat milk. They have glowing biofluorescent fur, poisonous nails on the backs of their legs and ten sex chromosomes as mammals are supposed to have two. They are one of only five existing monotreme species, creatures that came into existence millions of years before modern mammals ever appeared on the scene. Probably the world’s most bizarre mammal, its complete genome has been mapped by scientists. The exposure of its genes eventually explained how and why it developed some of its more extreme characteristics.
“Ovary mammals (monotreme) are the only existing mammalian outcomes for terriers (marsupials and euthanasia) and provide important insights into mammalian evolution,” said biologist Guojie Zhang of the University of Copenhagen. Earth.
Monotremes are technically mammals – with ‘technically’ the verb here. What they really are is a mashup of mammalian, reptile and bird genes that somehow worked out to help the platypus and four species of echidna (which looks like an outdoor heron) survive for so long . Sweet mammals, just like humans, produce young living things. Metatric mammals, or marsupials, carry their young in a pouch where they continue to develop until they are ready to roam alone in nature. Monotremes, also known as prototere, lay eggs but still produce milk for their offspring. That milk is secreted by their sweat glands.
How did it even evolve into a mammal or at least mammal-adjacent? Vitellogenin genes are proteins in the blood that form an egg yolk. It can be found in everything that lays eggs. Estrogen helps to form it in the liver, where it is adapted and then sent to the ovaries to be processed into the yolk. Humans and marsupials have lost these genes. As it developed, the platypus managed to cling to one, which explains why it lays eggs. It can get away with this, because the one vitellogenin gene that makes it makes its pups less dependent on dead proteins, as it also produces milk for it.
What the vitellogenin revealed in platypus genes is that milk production in mammals was transmitted from a common ancestor who shared the planet with dinosaurs more than 170 million years ago. His genome also gives away when he loses his teeth: when half of the eight genes needed for teeth only disappeared 50 million years later. Instead, horn plates are used on the inside of the diving bill to crush small crustaceans that are usually on the menu. Another question that Zhang and his colleagues were finally able to answer was how platypuses managed to retain the ten sex chromosomes of their ancestors. Euthanasia and marsupials have only one X and one Y chromosome, while the platypus has five of each.
What the team’s research suggested was that monotreme ancestors already had 10 Xs and Ys in a ring until they broke into smaller pieces. It is as far away from eutherians as we are that the sex chromosomes of a platypus are actually closer to those of chickens, but it still proves that we are somehow related to birds.
The coolest feature of the platypus may be the glow-in-the-dark fur. Biofluorescence occurs when wavelengths of light that are too short for the human eye to see are absorbed and then emitted again as longer visible wavelengths, causing the glow to happen. You often see this phenomenon in deep-sea fish, but in a (kind of) mammal? Platypuses are nocturnal creatures that usually crawl out when the sun is just setting and swimming with their eyes closed. This explains the electrical receptors on the bill that help it seek out prey. What it does not explain is why they need it when they do not even see each other, but by absorbing UV light, it can be less visible to UV-sensitive predators with almost natural night vision.
Although we always have to watch aliens, it’s a bit of a thought how strange some creatures that have built up and evolved here on earth can get.