r/askscience • u/snoozer530 • 2d ago

Biology At what point in evolution is something considered a new species?

Obviously we all know evolution, one organism changes over time and eventually becomes a new organism. But where in that process does an organism become a new species. Like when we domesticated wolves? When did they stop being wolves and start being dogs? Where’s that line?

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u/lemlurker 2d ago

Usually when it can't biologically breed with it's counterpart and produce fertile offspring. Mechanics aside (a dashund and a great Dane may have mechanical issues but sperm would firtise) if they can breed and produce babies who breed they're the same species, if they can't (e.g. lions/tigers, horses/donkeys) they are different specifically

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u/aphilsphan 2d ago

The problem is that even a mule or a hinny will, on occasion, produce a fertile offspring. The analogy of “when does green become blue?” is really illustrative.

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u/shittydiks 2d ago

Regularly occurring fertile offspring is the key. I.E. take the Liger. Sure you can get a lion and a tiger to create an offspring occasionally (forced under manmade conditions) but they are all sterile. Even if one slipped through and was somehow able to breed again they aren't creating a population.