Robin Dunbar suggests you should suspect someone who has more than 150 friends on Facebook   A professor of Evolutionary Anthropology at Oxford University has found out that human beings are physically limited to being able to link up and manage up to 150 friends at most, regardless of any other societal variables.   Professor Robin Dunbar's study revolves around his own theory, called Dunbar's number, which posits that the size of our neocortex - the part of our brain that is responsible for conscious thought and language - is too small to handle more than 150