Gregory Clark is chair of the department of economics at University of California at Davis. Some of his articles can be seen here...
http://www.econ.ucdavis.edu/faculty/gclark/research.html
His 26-lecture online course, Economic History of the World before the Industrial Revolution,available from ITunesU, is a detailed exposition of his research in world-wide wealth, health, violence and well-being of the human species...
https://itunes.apple.com/us/itunes-u/world-economic-history-before/id405570098?mt=10
He has published several books including The Son Also Rises, an analysis of wealth based on surnames, and A Farewell to Alms, an extensive analysis of historical wealth and health.