Why do we yawn?

Are mouth bugs nastier than bowel bugs? How would wiping out mosquitoes affect the food-web? What is an itch? Are anaesthetics a risk factor for blood clots? What are trans-fats and invert sugars? Can parasites manipulate our behaviour? Are there any benefits of yawning? Plus, news of the genetically-modified mosquito that might help to eradicate malaria... Like this podcast? Please help us by supporting the Naked Scientists