You know who Kevin Federline is, don't you? Why, for heaven's sake? In what way has hearing about K-Fed's career and family troubles made any of our lives more interesting or fulfilling? What about Heidi Montag? Or Jon Gosselin? Nicole Ritchie… anyone?
Our age isn't unique in promoting people who are famous only for being famous. During the Depression, Americans followed avidly the doings of Brenda D.D. Frazier, whose two known talents were having a very rich father and modelling underwear. Go back a century and you find people wondering intently what new kind of overcoat Viscount Petersham would wear this year. Earlier still, King Richard the Lionheart enjoyed great popularity among a peasantry whose only contact with him was paying his punitive taxes. And of course the Caesars provided all Europe with the essential aspects of celebrity: power, madness, sexual excess, violence, and good grooming.
Interest in gossip about the rich and famous is a universal human quality - and not just human. Other primates are similarly obsessed with the lifestyles of top tribe members. An experiment with male macaque monkeys found that they were willing to give up lots of delicious treats just to look at pictures of high-status males; the only other images similarly worth paying for were of female bottoms.
Dominance and breeding fitness are important things for a primate to know, because they help determine the individual's own opportunities and risks. Any monkey who can't tune in to the local social structure is going to miss out, not just on the gossip, but on the chance to survive and reproduce.
So, when the media tells us that somebody is hot (or rich, or influential) we can't help but respond: we want to know, because we need to feel connected to power in this, our global tribe.
The problem with celebrity, though, is that it is a one-way relationship. Robin Dunbar of Oxford University looked into the social networks of primates and found that there is a firm upper limit to the number of other individuals one can know as individuals - and for humans, that limit is 150. It's the size of most people's Christmas card lists, or the number of Facebook friends who really are friends. Beyond 150, new acquaintances just shade off into the mass - we don't really know them.
This means that the more attention you pay to Kevin Federline, the more likely he is to take up one of those 150 places - and the less likely that place is to be occupied by a potential real friend who would also know you. Celebrity hijacks our social instinct, designed for getting along in small groups, and ties it to essentially empty imaginings of a fictitious relationship. We know so much about the great that we can easily envisage ourselves hobnobbing with them – which can make real life seem unsatisfactory by comparison. Bad as this is for us adults, it's far worse for children: a kid whose friends are all media figures is essentially more lonely than one whose friends are imaginary.
Our partners, our relatives, our neighbors and workmates may not be glamorous or wealthy, but they can offer something that Angelina Jolie or Tom Cruise never can: they actually care about us. They know who we are. That should always be the hottest gossip. That is truly worth celebrating.