What would you do with a third thumb? Research suggests our brain can quickly adapt   Birds can dream - and even have nightmares - and now scientists are tuning in A comprehensive new collection of medical information shows the health risks of space travel A study in mice sheds new light on how exercise can reverse aging in the brain Rare fossils from the ‘age of monotremes’ found in Australia  How the brain can instantly tell the difference between speech and music PODCAST EXTRAS Organic farms next to conventionally farmed fields leads to increased pesticide use Orca whales hunt, play and dive – one breath at a time The secret of the beaver’s orange teeth can help us make our teeth strong