While there isn't a specific sleep gene, scientists studying the sleep habits of fruit flies have found evidence suggesting a strong genetic component.

The genetic component is essentially a write-off - there's precious little we can do about this until gene therapy or some equivalent lets us adjust our pre-set happiness levels.

"Handedness has a genetic basis, but like other complex traits - height, weight - it is complex," he said. "it's not a single gene that leads to it."There's a strong environmental component, too.