When did we all start sleeping like this? Slumbering dragons hold clues.

Reptile sleep patterns might not actually be all that different from our own. Sleep patterns thought to be used only by mammals and birds have now been discovered in a non-avian reptile, the Australian bearded dragon. Finding those patterns, slow-wave sleep and rapid eye movement (REM) sleep, in a reptile could dramatically revise scientists' models of how those sleep patterns evolved. In fact, they may have evolved over 300 million years ago. "The status quo, until our study, was that these features of sleep only exist in mammals and in birds," Gilles Laurent, director for the Max Planck Institute for Brain Research in Frankfurt, Germany and an author of the new paper announcing the findings in the journal Science on Thursday, tells The Christian Science Monitor in a phone interview.