Great concise article.

It's interesting how small humanity's core and even extended groups are. Modern civilization and population density is very recent in evolutionary terms, and our brain's just can't make good use of that much humanity.

But even the casual circle is interesting, I think of everybody on LinkedIn as a kind of casual circle. Business casual, where we're all advertising our business acumen to each other. Both as desirable employees, and as desirable people to work for.

Do large twitter circles advertise casual habits? To what end?

The most interesting aspect which they did not mention - how the nuclei of close contacts look like in the broader view. I wonder how it globally forms a high-connectivity core.

Here is a popular article about the characteristics of networks if someone is interested:

http://scitation.aip.org/journals/doc/PHTOAD-ft/vol_61/iss_1...

One of the things I found most interesting was that out of the 140 friends on Facebook that on average people have, only 7 of those friends are communicated with via wall posts and messages. There is irony in the fact that although online networks reduce friction in communication, the communication is very infrequent.

Interesting article