There’s a not-too-subtle similarity between the leading GOP candidate, Donald J. Trump, and the alpha male Russian president Vladimir Putin. Both are primarily ruled by testosterone, says biological anthropologist Helen Fisher. Meanwhile, America’s estrogen candidate isn’t who you might expect. Hillary Clinton is too warlike and direct to claim the title. She falls between the barbarism of Trump and the soft, grandfatherly Bernie Sanders. These differences in biology help determine a candidate’s personality and therefore what kind of people they attract to their campaigns.