The three most disruptive transitions in history were the introduction of humans, farming, and industry. If another such radical transition lies ahead, a good guess for its source is artificial intelligence in the form of whole-brain emulations, or “ems,” sometime in the next century. Drawing on academic consensus from many disciplines, a baseline scenario set modestly far into a post-em-transition world can be outlined. The scenario takes into account computer architecture, energy use, cooling infrastructure, mind speeds, body sizes, security strategies, virtual reality conventions, labor market organization, management focus, job training, career paths, wage competition, identity, retirement, life cycles, reproduction, mating, conversation habits, wealth inequality, city sizes, growth rates, coalition politics, governance, law, and war.