Recent research has shown that it can be an advantage for animals and for humans to be left-handed. Being able to do things differently from most people can be a great help in many sports, such as tennis or fighting with swords. Left-handed people from Norse settlements in Ireland in the 10th Century were more favoured than right-handed people as they had the advantage of swinging with their left hand as they were on a horse or running down the stairs of a castle in attack or defence. 