Why Did Eurasians Conquer the World?

Diamond argues that primitive peoples who still live semi hunter gather life styles, are at least as smart as people living in advanced economies. He actually argues that new guineans might even be smarter, since he assumes they have so many more problems to solve day to day just to survive than typical new yorkers or londoners. But diamond's argument really isn't racial whatsoever. I think he's just over compensating a little here. Ultimately, he explicitly assumes that intelligence is not the important historical variable that enabled urasian societies to overwhelm other societies.