Although I appreciate this kind of reasoning in general, I think it can be misleading when applied to animal behavior. What prevents one of the reasons we slee

Although I appreciate this kind of reasoning in general, I think it can be misleading when applied to animal behavior. What prevents one of the reasons we sleep to be absent from the set of reasons jellyfish sleep? Also, wouldn't it be surprising if a behavior as complex as sleeping had only one reason, or if the main reason today would be anything like the main reason back in the days were the common ancestor between us and jellyfish lived? And so, shouldn't we expect that we sleep for different reasons?