It revealed that tabby markings—the blotches on some house cats—didn’t come along until the Middle Ages.

它揭示了虎斑斑纹——一些家猫身上的斑点——直到中世纪才出现。

You can also use the negative form—didn’t use to—to talk about things that weren’t true in the past, but are true now.

你也可以使用否定形式— — didn' t used to—— 来谈论过去不真实但现在真实的事情。