Research by Robin Dunbar, professor of Evolutionary Anthropology at Oxford University, shows that throughout history the human brain can only handle about 150 friends. More than that and the relationships might be less meaningful. This fact is known as the Dunbar Number.The number could be of particular interest if you’re from Argentina or Hong Kong. According to a Plaxo, Inc., creator of the smart address book, an Argentinian has on average 479 contacts in his/her address book. In August 2006, Plaxo released their Connected Index which ranks the level of connectedness between people, country by country, based on the average number of contacts in their Plaxo smart address book.