It looks like population growth given the dates and where the data is, though I don't get the arches unless it's showing some kind of internal migration.
Basically....the blue is birth and red dot is death and the line is the migration that connects the two.
How Cultures Move Across Continents : Goats and Soda : NPR
Well, I didn't do too bad, especially since I can't even see the red very well (partially colorblind).
Yeah that was very good. The dates made it hard to figure out.
And I actually saw the article and thought hey I saw that image somewhere.