When low­er pri­mates form a hier­ar­chy, those at the bot­tom under­go a change in their dopamine sys­tem. This makes them more like­ly to con­sume drugs in an addic­tive fash­ion. Now, if this turns out to be true of our species, that would mean that human beings are par­tic­u­lar­ly vul­ner­a­ble if they’re in some way dom­i­nat­ed or don’t have any pow­er.