Question: Dear Dustin, why do you think that the platypus and echidna are mammals and lay eggs? Thanks, twright1

  1. Hi twright,

    This is a very good question.

    It appears that all mammals came from ancestors that were egg laying animals. The further we go back in time, the mammals that we now know, were in fact more like reptiles. They didn’t have hair, instead they were scaly, and instead of having live birth, they laid eggs.

    So monotreme’s, that’s the word for echidnas and platypus, appear to have descended from an old group of mammals that laid eggs, while other mammals evolved to have live birth.

    It is just like some reptiles that lay eggs, while other reptiles have live young.