For both foragers and farmers, social connections and status relations established as a teen and young adult lasted for a lifetime. So it made great sense to invest in such things. In the high-mobility upper-class US today, however, people move from high school to go to college, and then move somewhere else for a job; their investments in earlier friends gain them much less. And it seems like behavior hasn’t updated fully to this new situation – it seems young adults invest too much in developing friendships and local status that they will soon lose.