Will a cold onion make me cry less?

Why are humans still born with bits we don't need - will evolution do away with them? Did an onion make me cry less because it was cold from the fridge? Do animals get diabetes like humans do? What is the physics of a rainbow? Where does lightning come from? What did cloning Dolly the Sheep mean for me? And is Covid-19 nature redressing the balance? Dr Chris Smith and Relebogile Mabotja have the answers...