My clan were supposedly all left handed. More recent thinking is that they actually learned to be left handed because this gave them a tactical advantage in hand-to-hand fighting. The family strongholds in the Scottish borders were built to suit and be defended by left-handed people.
My elder daughter is left handed and two uncles were also 'lefties'.
At primary school, when we still had 'dipping pens', there were special pens for left handers. Some people have said that this was very progressive - even in the 1950's.