Half-life of friends: 7 years

LiveScience details the completely unsurprising fact that we tend to replace half of our stable of close friends about every seven years, and we tend to find new friends in the same places we got our old ones.

Stunning.

I'm not sure what this means in the era of MySpace and Facebook, where little effort is required to tag someone as a "friend", and maintaining the "friend" designation takes even less trouble. Without getting into the qualities and qualifications of what constitutes a "close" friend, it's difficult to apply any real-world test to this data.

I wonder if the whole thing doesn't take us back to caveman days, when we operated in smaller clans, and if you got too small self-defense became a challenge, while growing too large meant difficulties in transport, nutrition, and other pack-like events.