This made me ask, "since platypuses lay eggs, they must not have internal pregnancies, but if that's the case, then what causes them to start producing milk?",

This made me ask, "since platypuses lay eggs, they must not have internal pregnancies, but if that's the case, then what causes them to start producing milk?", and I don't have an answer yet, but I did just learn that they don't have nipples and instead they just sort of "sweat" milk. (Also they have no sweat glands?) Another relevant fact seems to be that they don't lay unfertilized eggs. So maybe they do have pregnancies of a sort. Answers.com, not the best source (also not the worst), asserts [1]: > Fertilised platypus eggs stay in the mother's body for around 28 days, although lack of research means this has not been determined definitively. The eggs are incubated by the mother curling around them and keeping them warm and dry in the chamber of the burrow for another 10 days. I'm not sure I get the point of the egg if the majority of the pregnancy is internal anyway. Maybe evolution is just random. [1] https://www.answers.com/Q/How_long_is_a_platypus_pregnant_for https://www.answers.com/Q/How_long_is_a_platypus_pregnant_fo...