Imagine the original job interview. The first one ever, back on the prehistoric savannahs of eastern Africa. It wouldn’t have been exactly like a modern job interview, because early humans had no resumes or Linked-In or letters of recommendation to guide them. There was very little in the way of personal or professional reputation to go on, so in that sense the exchange was much trickier. But the fundamental idea was the same: Somehow the interviewer had to judge, in a brief spot of time, if the applicant — a complete stranger — was worthy of trust.