And rightly so. First, penguins are birds. Birds are not mammals. Even some mammals like dolphins have very different sleep patterns (dolphins sleep one hemisp

And rightly so. First, penguins are birds. Birds are not mammals. Even some mammals like dolphins have very different sleep patterns (dolphins sleep one hemisphere at a time and can still swim up to take a breath while sleeping). We don't exactly know the last common ancestor of birds and mammals, but it is theorised it happened about 220 MYA. It was so far back in the past, Earth only had one large landmass and the dinosaurs did not yet even appear. Second, birds have tens of millions of years of evolution doing things like flying non stop for days. There would be a lot of selective pressure to evolve birds that are good at being able to do micro sleep without crashing down.