Why are Platypuses conspired mamals if they lay eggs?
In: Biology
They’re a sub-classification called monotremes. Echidnas and platypuses both are; warm blooded, fur or hair, produce milk (although neither have nipples), but lay eggs.
Echidnas also have a pouch
Because they produce milk to feed their young. Developing eggs inside isn’t really a prerequisite for being a mammal.
Sharks develop in the womb and they aren’t mammals.
300 million years ago there was a creature with fur that gave live birth. Scientists decided to call that a mammal. Any creature decended from that origional mammal is a mammal, no matter how else they evolve. What traits a species has doesn’t matter, all that matters is it’s lineage.
The biggest defining feature of mammals is that they produce milk. Most mammals have live births, but that’s not what defines a mammal.
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Mammals produce milk. All early mammals would have been egg laying as mammals evolved from egg laying reptiles.
Classification in biology is based on ancestry of the species. While animals in the same kingdom or family will typically have similar traits, the traits present in the current species is not how they are classified.
Because of this, animals end up with a classification that seems to break the rules, when in fact it just took a different evolutionary path from the defining ancestor.
> Mammals (from Latin mamma, ‘breast’) are a group of vertebrate animals constituting the class Mammalia (/məˈmeɪliə/), and characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones.
From [wikipedia](https://en.wikipedia.org/wiki/Mammal).
The important things to make a mammal a mammal are actually not related to giving live birth.
The important bits are hair, the structure of the ear and brain, and making milk.
There is another category within what we call mammals, called therians, and thats where the live birth thing comes in. The vast majority of modern mammals are therian so thats where the confusion comes in.
Its like if you had only ever seen red balls in your life, and then someone shows you a yellow ball. “But all balls are red” you say, but its really just that *most* balls are red, and that the redness and ballness arent necessarily related.
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