06/12/2010 05:12 am ET | Updated Nov 17, 2011

Six Degrees of Separation -- Becoming Fewer Through Social Media?

The world population is about six billion, and yet there are supposedly no more than six degrees of separation among all of us. This theory was known well before the Broadway play of the name or the Kevin Bacon game of recent years. Guglielmo Marconi, in a 1909 Nobel speech, suggested the number 6 (well, 5.83) as connecting everyone together in a radio network.

Stanley Milgram measured connectivity in Americans and indeed discovered that only a small number of connections, especially through hubs and portals like the world wide web, interlink the entire population.

All of us have examples of surprising connections. At Gatwick airport, 20 years ago, cabs were few, and I agreed to share one with a nice young student. We were both going to London. We were both going to northwest London. We were both going to Hampstead Garden Suburb. Both to a street called Wild Hatch. Both, it turned out to our shock -- and the cab driver's -- to the same house. The mother was my friend, the daughter was the student's, and we surprised both, and ourselves.

There's an evolutionary theory that our brains were wired to cope with about 150 close contacts, and that we wouldn't be able to keep track of all the relationships, or have the brain power to care about more. Hunter-gatherer villages topped off at about that size, and so do most Web site cohorts, according to studies.

On Facebook I've noticed many friends lists seem to top off at about that number. But there are amazing exceptions -- people with huge numbers of "friends." I doubt all these people know each other, but Twitter and other social networking devices are stretching the numbers of connections we make into the thousands.

So according to the experts we are only separated from the rest of the world by no more than six others. But twenty-first -century networking may be making it even less.

Anyway, do you have any examples like the unexpected connection I made at Gatwick airport?

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