If people like this were any kind of reflection of our ancestors, there would be no industrial age, no farming communities, no ships at sea. However, everyone would know exactly and with great precision what that look from that person across the community fire really meant, whether it was a "I like you look" or "I'm kind of iffy on how you much I like you" or "You smell really bad," as they ate their dinner of fruits and berries (no meat for these folks!).
Could be the people don't want the human race to go extinct.