Try the platypus. You can almost hear the calm voice of David Attenborough describing such a special creature, the mystery of how it came to be has given scientists too much attention.
Platypuses may be alien life forms on Earth. They lay eggs. They suck milk. They have glorious biofluorescent fur, poisonous spikes on the backs of their legs, and 10 sex chromosomes when mammals are thought to have twins. They are one of only five species of monotremes, creatures that evolved millions of years before modern mammals appeared. Now, this is perhaps the rarest mammal in the world that scientists have mapped out its entire genome. The emergence of his genes has finally explained how and why he developed some of his most isolated traits.
“Egg-laying mammals (monotremes) are the only mammalian group of therians (marsupial and euphoric animals) and provide key insights into mammalian evolution,” said University biologist Guojie Zhang Copenhagen, who recently co – authored a study published in Nature.
Monotremes to mammals are technically – with “technically” as the working word here. What they really are is a mashup of mammalian, reptilian, and bird genes that worked in some way to the platypus and four species of echidna (which resemble a kind of exotic hedgehog) to keep alive for so long. Eutherian mammals, like humans, give birth alive. Metatherian mammals, or marsupials, carry their young around in a bag where they develop so that they are ready to go around the wild on their own. Monotremes, also known as prototherians, lay eggs, but still make milk for their offspring. That milk is secreted through their sweat glands.
How did this develop even in something that is mammals or at least close to mum? Vitellogenin genes are proteins in the blood from which egg yolk forms. They can be found in anything that lays eggs. Estrogen helps to form them in the liver, where they are modified and then sent to the ovaries to be processed into what becomes yolk. Humans and marsupials lost those genes. As it turned out, the platypus was able to hang on one of them, which explains why it lays eggs. He can get away with this because the same vitellogenin gene he has made so young is dependent on yolk proteins because he also makes milk for them.
What the vitellogenin in platypus genes has revealed is that milk production in mammals was inherited from a common ancestor who shared the planet with dinosaurs more than 170 million years ago. His genome also gives way when he lost his teeth: when only half of the eight genes needed for teeth disappeared just 50 million years later. Instead he uses horn plates on the inside of his duck bill to grind small barks that are usually on the plate. Another question Zhang and his colleagues could finally answer was how platypuses ruled the 10 sex chromosomes of their ancestors. Eutherians and marsupials have only one X chromosome and one Y, and the platypus has five of each.
What the team’s research suggested was that the 10 Xan and Ys were in a ring of monotreme ancestors until they broke into smaller pieces. This is so far removed from eutherians like us that platypus sex chromosomes are closer to those of chickens, but it still proves that we are related to birds in some way.
Perhaps the coolest feature of the platypus is the glow-in-the-dark fur. Biofluorescence occurs when light waves that are too short for human eyes to see are then captured as longer, visible waves, which cause that glare to occur. You often see this wonder in deep-sea fish, but mammal (sort of)? Platypuses are nocturnal creatures that usually creep out when the sun is just setting and swimming with their eyes closed. This explains the electrical receptors on his bill that help him seek prey. The thing is that it doesn’t explain why they need it when they’re not even seeing each other, but by absorbing UV light it can be less visible to UV-sensitive predators with night vision almost before.
While we keep an eye out for monsters, it ‘s kind of mind blowing as alien as some of the creatures that spawned and evolved here on Earth.