Topic summary
Hibernate
Extracted from the Wikipedia article Hibernation.
In endothermic animals
There is evidence that hibernation evolved separately in marsupials and placental mammals, though it is not settled. That evidence stems from development, where as soon as young marsupials from hibernating species are able to regulate their own heat, they have the capability to hibernate. In contrast, placental mammals that hibernate first develop homeothermy, only developing the ability to hibernate at a later point. This difference in development is evidence, though inconclusive, that they evolved by slightly different mechanisms and thus at different times.