A graph of the populations of Ireland [left axis] and Europe [right axis] indexed against date. (Taken from Wikipedia)
This graph is related to the recent news about the Irish Potato Famine of the 1840’s (see link to news). Apparently they sequenced the genome of the old pathogen and found that it is new to science; it is markedly different to the potato blight that exists today. The old potato blight might now be extinct.
Reading about the famine on Wikipedia, I was struck by this graph which shows just how badly the blight affected census numbers around that time. Millions of Irish were forced to leave for overseas; I was surprised at how many fled to my local neck of the woods, in the Ottawa/Toronto area.