[netman21]

This rambling summary article touches briefly on "natural selection" but no one has yet to look into what seems obvious. In mammals where most parents have to care for their young, if the young did not sleep, did not give their parents a break for long periods, they would not survive. Therefore sleep is selected for. Those offspring that sleep survive, passing on the sleep trait, to their offspring. - Source: parent.

[agentgt]

While I agree that sounds like a plausible theory (and sort of reminds of the domestication theory... ie cute animals get more parental and human focus) but there are just too many animals that barely take care of their young that still sleep.... for example sharks sleep.

[erroneousfunk]

Also, why would we keep on sleeping into adulthood if it was such a massive risk and waste of resources? It doesn't make sense that adults also sleep when they're "getting a break from their kids"