Tech capacity in 1500 determines development today

Was the wealth of nations determined in 1000 BC?

This is an interesting graph from a paper by Comin, Easterly and Gong. I suppose the anomalous points for the USA, Canada, Australia and New Zealand are explained by the change from indigenous populations in 1500 to populations primarily composed of European immigrants and their descendants in 2002. Argentina, Uruguay and Mexico, while not as successful as the countries with institutions derived from Great Britain, are also more successful than the technology capacity of their inhabitants in 1500 might have predicted. The British Isles and Scandinavian nations in the upper right hand cluster are also more successful than the regression line might suggest, implying something about culture perhaps.