Why have social media sites like Twitter and Facebook become so popular? Facebook, as the internet’s second most popular web site, seems to be catching up to search giant Google. Now science provides an explanation.

A new article from the New England Complex Systems Institute says that as the internet grows to contain more and more information, our approach to finding the information we want is naturally shifting to resemble another complex system – the human brain.

The article, which can be found on NECSI’s web site at necsi.edu, also has two clickable “Tweet Maps” showing the network structure of tweets, retweets, and blogs of two recent science news articles. The maps show network location and number of followers for hundreds of individual tweeters.

When the internet was new and did not have as much on it, searches made sense for most purposes. Now, the internet contains huge amounts of rapidly changing information. So our society is shifting from searching to identifying and following people whose information picks work for us through Tweets, Shares, Likes, and other ways of highlighting material.

This information sharing is similar to the human brain, in which each neuron receives and sends signals from and to particular other neurons. “Individuals running searches can no longer cope with all that the internet has to offer,” NECSI President Professor Yaneer Bar-Yam said, “Social media sites are a way of tuning in to information more likely to be relevant.” This does not mean searches are about to disappear, just that they will be used for more limited purposes.

The article also suggests that social media sites can serve as maps of our society, not by capturing social relationships but by describing information flows that people use to function and make society work.