The male sleeps longer than the female, is more likely to sleep during the day and the female is more likely to have her sleep disrupted. Sounds familiar? This is research into fruit flies (Drosophila melanogaster) rather than the adult human male (couchus potatus), but it casts a light onto our own propensity to kip.
For a start, sleeping behaviour is hard wired into living creatures. It's written through us like a stick of rock. The humble fruit fly, the hapless butt of so many experiments, has 1,700 genes associated with sleep patterns. These might affect when and for how long an individual fruit fly might snooze. Mess around with these genes and sleep patterns are altered.
What should we make of this? Does the long sleeper have a genetic drive for such inclinations, in the way they might have their own thumbprint or eye colour? Is there some ancestral sleeper who has passed on these habits? Why should the comfortable kipper be turned out of bed when their genes are telling them they need just five more minutes?