Study : Ancient people were fewer in number , but burned 10 times as much land . ' Lead study author William Ruddiman is a professor emeritus of environmental sciences at the University of Virginia and a climate scientist . Ruddiman : They could slash , burn ` ` five times in a ten year period '' Ken Williams , a climate scientist , to study exaggerating impact of early man .
Study : Ancient people were fewer in number , but burned 10 times as much land . ' Ruddiman : They could slash , burn ` ` five times in a ten year period '' Ken Williams , a climate scientist , to study exaggerating impact of early man .