Four wings good, two wings bad: An artist's impression  of Sapeornis, a genus of primitive bird that lived 125 to 120 million years ago. About 33cm from head to tail, it had feathered fore and hind limbs. The reconstruction is based on fossils from northeastern China.  Illustration: Yike Zu

The earliest aircraft relied on two sets of wings to get airborne and so too did the earliest birds it seems. Palaeontologists in China have identi(...)