Until 300 years ago, before mammals evolved to their current stage, and due to all mammalβs having similar physical appearance as a fetus, sometimes a random species would be born from certain mammals.
A polar bear would give birth to a monkey, a giraffe birth to a whale, a dolphin birth to a kitten, and so on.
That is why to this day, animals understand each other so well.
Another Fun Fact from Mr. Science.
What you said