Platypus is obviously a mammal, but it actually lays eggs. In 1799, when the British zoologist George Shaw first received a specimen of a platypus creature, his first reaction was to think that someone was playing a prank on him!
Because the platypus looks like a monster, it has a wide mouth, very similar to a duck's mouth, and it also has two nostrils on its mouth, and its whole body has thick brown hairs. Its limbs are very short, with hooks and claws on its five toes, membrane-like webbing between its toes, resembling a duck-footed god, and its ankles are covered with venom-filled spines.
If you see the platypus for the first time, you'll think it's a monster because it's so weird in appearance. Platypus is the oldest and most primitive mammal in existence. Scientists are trying to isolate it from mammals through research (genetic testing). But as the research progressed, scientists began to ponder the question, is the platypus really a monster? Or that it is normal, and other mammals are the real "monsters", including us humans.
Platypus and echidnas are the world's only two remaining single-porous oviparous mammals native to Australia. Unlike other mammals, platypus has only one cloaca, no separate urethra, birth canal, anus, etc., retaining the most primitive structure of mammals. About 187 million years ago, monoporous animals diverged from other mammals. Platypus, a single-hole trait that seems strange to us, may have existed in our common ancestors, but after differentiation and evolution, the single-hole trait disappeared from our ancestors and other mammals.
Birds, like insects, have multiple copies of a gene called yolkin, which is associated with the production of egg yolks, and most mammals do not have pro-yolk genes. In 2008, scientists sequenced platypus genes for the first time, and according to the newly discovered genome, platypuses have copies of pro-yolk protein genes, which helps explain why platypuses lay eggs abnormally. Studies have found that copies of the original yolk protein gene, which may have been lost by our ancestors and other mammals, are not monoporous innovations.
In addition, platypus also has genes similar to those of other reptiles, which explains their poisonous foot. We mammals usually have only one pair of sex chromosomes, but single-hole animals have very strangely five pairs of sex chromosomes, and other mammals may have lost four pairs of sex chromosomes in the process of evolution. The newly discovered genome structure of the platypus suggests that these chromosomes were once ring-shaped and have since split into fragments for unknown reasons.
According to a study of the platypus genome, platypuses and other mammals, including our ancestors, were single-porous organisms tens of millions of years ago. Later other mammals evolved to form the now diverse mammalian world. After tens of millions of years of development, the platypus has not changed much, retaining the most primitive single-hole traits of mammals, which can be said to be a veritable living fossil. It's not so much that platypuses are monsters, but rather that our other mammals evolved to become "monsters." After a bit of research and comparison, scientists found that the "clown" turned out to be ourselves...