A monkey eating ice cream. Credit: Anindito Mukherjee / European Pressphoto Agency

With all of our iPhones, Facebooks, Twitters and other wonders of modern technology, we’ve certainly come a long way from our primate ancestors. But our biology apparently hinders us from becoming the extreme social butterflies that social media theoretically enables.

Some have suggested that online social tools provide a way for people to expand their relationships further than ever before. While we can certainly reach a wider audience more easily, scientists believe the number of real friendships that any one person can maintain remains largely the same. Based on research of ape behavior, humans apparently can’t handle more than about 150 in their inner circles. The theoretical limit is called Dunbar’s number.

The Economist interviewed Cameron Marlow, Facebook’s in-house sociologist, to see how social interactions on the website compare with the Dunbar’s number hypothesis. Marlow says core friendships haven’t appeared to change much. Even folks with hundreds or even thousands of Facebook friends interact regularly with …

… only a small group: