Why do platypuses lay eggs even though they are mammals?
They are definitely very unusual. I do know that they are mammals since make milk, as mammals got their name from mammary glands, not how their babies are born.
- ZirpLv 712 months ago
So we know that genetic reality is not black-and-white
- Anonymous12 months ago
Mammals evolved from a reptile, a cynodont therapid reptile. Reptiles lay eggs. The fact that the platypus has fur and milk and is warm blooded showed that these mammalian features evolved before live birth. Live birth has in fact evolved independently many times in reptiles,. For example, vipers, garter snakes, and some lizards have all evolved live birth.
Most egg-laying mammals have gone extinct, having been replaced by mammals that evolved live birth. The platypus is found in Australia, and Australia was once part of the super continent Pangea, which included Europe, Asia, North and South America, Africa and even New Zealand. Later Pangea broke up into separate continents, Australia became isolated quite early, before placental or marsupial mammals evolved, New Zealand in fact separated from the other continents before mammals even evolved. About 65 million years ago, a giant meteor the size of Mt. Everest struck the earth at high speed. The impact was the equivalent of 1 billion atomic bombs exploding at the same time, and it created oven-like temperatures on the ground. All dinosaurs, all enantiornithine birds, all marsupials in North America and Europe were wiped out. The only animals that survived were those who spent a lot of time underground (e.g. toads, snakes, lizards, salamanders, shrew-like mammals, marsupial shrews) or they were in or near the water (e.g. fish, turtles, frogs, newts, crocodilians, shorebirds that later became the ancestors of all living birds, and of course the platypus). The reason is that heat rises, so animals that were underground were not fried. Water also takes a lot of energy to heat up even just 1 degree, and so animals that were in the water were able to avoid being fried. Later, the marsupials recovered in South America, evolving from the surviving marsupial shrews, and shrew-like mammals in Eurasia, North America Africa also evolved into the living mammals we see today. Later, some marsupials migrated to Australia from South America across the Antarctica land bridge when it was not yet frozen.
- MorningfoxLv 712 months ago
Platypuses split off from other mammals very early ... at least 166 million years ago, maybe 220 million. The other mammals went on to develop internal embryos and placentas. Although kangaroos, opossums, spiny anteater, koalas, and a few others, did manage to get along fine without placentas.
- Steve HLv 612 months ago
This is one means by which we know evolution works.
Some species evolve due to changes in their environment or food sources. Others either don't need to evolve past a certain point, as there would be no benefit to them.
If we look far enough back, mammals evolved from reptiles.
Most reptiles still lay eggs as their ancestors did originally.
The platypus and echidna are both of the group monotreme, which is an ancient type of mammal. Therefore they are the exception to the typical live birthing of mammals.
The other two groups of mammals are marsupial and placental.
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- Anonymous12 months ago
'Cause THAT'S the way God made them ................................
- 12 months ago
Platypuses are egg laying mammals it's an exception