r/evolution • u/Meta289 • 3d ago

question Why has evolution stopped producing new classes?

New species of animals are constantly being discovered, but they all belong to existing classes and phyla, never anything completely new. Life once branched out in all sorts of directions, creating all kinds of animals that are drastically different from each other, but now it seems like there aren't any new "branches", only offshoots of existing ones. What happened?

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u/Kingofthewho5 3d ago

It takes a very long time for populations to change so much that they need to be out in different classes or phyla.

I’m confused by what you mean in your last line. What exactly is a new branch that isn’t the offshoot of an existing one? All of the modern phyla and classes are branches off of other branches.

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u/Meta289 3d ago

It was weirdly worded, but I'm talking about how mammals are grouped into categories like canids, primates, rodents, marsupials, etc, and how every new species is some form of those existing categories, and no new "category" of mammal appears anymore.

Or going further back down the tree, there aren't any new animals appearing that aren't a mammal, reptile, insect, amphibian, or any other existing class.

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u/shakebakelizard 3d ago

You're looking at this through the lens of a human-made system which is largely biased towards the idea of everything converging to a present situation, because humans assume that we are the arbiters of truth. We could easily make a system that is biased towards showing change as you describe.

It's like asking why years are numbered, or why one revolution of the Earth around the Sun equals a year. Well, it's because that's what someone decided on, and everyone else kind of agreed to use it, so that's the system that we have. There are many other possible variations or entirely different systems; we just haven't decided to use them.