Yet her story is not just about sex. As the title implies, at least half of it is the city. If Carrie lived in rural Kentucky rather than Manhattan, we wouldn’t admire her, but consider her lifestyle “trailer trash.”

Many would attribute this strange dichotomy to bias and perhaps there’s some truth to that. However, there’s a growing body of evidence that cities and the social activity that they catalyze are the key to our future. Even with our ability to connect across great distances, it is our local environment that spurs innovation.

The sociology of cities

Cities have a sordid history. Dickens chronicled their rise accompanied by increased proliferation of sweatshops and poverty. So it wasn’t surprising that as cities started advancing rapidly at the beginning of the last century, their onward march was viewed with trepidation.

Louis Wirth made the first major effort to analyze the effect of cities on our social fabric in his classic 1938 essay. He argued that the increased density of metropolitan areas led to specialization and diversity, which in turn broke traditional bonds of social cohesion and replaced a network of primary contacts with secondary relationships.

(Ironically, Malcolm Gladwell recently made similar arguments about social media with respect to political movements)

The vision of cities that Wirth presents is one of moral and social decline, where individuality is replaced by “categories,” meaningful conversation by mass media and social involvement giving way to detachment. For him, Carrie’s dalliances are symptoms of the city’s dehumanizing effect.


The ecosystem of the city

In 1960 a magazine writer named Jane Jacobs published a book, The Death and Life of Great American Cities, with an altogether different view. In her telling, it was the diversity of cities that made them vibrant and innovative.

She described neighborhoods that were kept safe by constant usage. The mix of people coming and going, the variety of people and businesses and the organic way that cities go through decay and rebirth, all combined to create both stability and vitality.

What made Jacobs’ view so revolutionary is her critique of urban renewal. In her view, the economic life of the city wasn’t dependent on big infrastructure projects or tax incentives for businesses, but in the promoting the same diverse culture that Wirth decried.

For Jacobs, it was the mixing of people and their ideas on sidewalks, cafes and bars that held the key to prosperity.


A tale of two cities

Most of the stuff that we’re really excited about at the beginning of the 21st century can trace its roots back to the early 20th century and just two cities: London (by way of its exurb, Cambridge) and Budapest.

Cambridge was the home of Cavendish Laboratory, which pioneered both quantum physics (the stuff of computer chips and lasers) and genetics. At the same time the Bloomsbury group was revolutionizing ideas about literature, number theory, logic and economics through it’s luminaries such as E. M Forster, G. H. Hardy, Bertrand Russell and John Maynard Keynes.

While growing up in Budapest, future Nobel prizewinning physicist Eugene Wigner developed an inferiority complex in math class sitting next to his schoolmate John von Neumann who invented both game theory and the modern computer architecture.

He might have felt the same way if he next to the somewhat younger Paul Erdos who, among other things, pioneered concepts in network theory or John Hasarnyi who recieved his own Nobel for helping to complete von Neumann’s work by introducing random variables to games.

There were, of course other cities of particular note, such as the Vienna of Freud, Wittgenstein and Gödel. However, it is astonishing that a century later we can trace most of the really important ideas back to just a handful of places.


The flat world vs. the spiky world

In 2005, Tom Friedman published his book announcing that The World is Flat, It occurred to him that the increase in global connectivity was making it possible for anyone anywhere to be as productive as people in places like pre-war Budapest and Cambridge and post-war America.

I’ve spent most of my adult life in emerging markets and I see what he means. In Ukraine, you can hire a 20 year old girl who looks like a supermodel, speaks five languages and can do econometric modeling for $200/month. Talent isn’t exclusive to any geographic area, why should innovation and the wealth that comes with it?

Soon after Friedman’s book came out, Richard Florida published an article (pdf) in The Atlantic proclaiming that the world is not flat at all, but “spiky.” What he meant was that while innovation could happen anywhere, the fact is that it’s concentrated in relatively few places and the disparity is increasing, not decreasing.

Even more striking is Florida’s explanation of why some places are more innovative than others. According to him, it takes more than research labs and universities, but a cool music and art scene, tolerance toward people of varied lifestyles and other soft qualities. As Jane Jacobs said, “When a place gets boring, even the rich people leave.”

Ideas having sex

If Carrie Bradshaw was young and nubile in the sixties, she probably wouldn’t have moved to New York, but San Francisco’s Bay Area. That’s where all the sex was going on! Free love. Smoking dope. Tie-dye shirts. The whole scene.

But that’s not all. Many of the ideas pioneered by the guys in Budapest and Cambridge combined to make products there. As Matt Ridley puts it in the video at the bottom of this post, those ideas had sex.

In other words, it was exactly the aspects that Louis Wirth lamented about cities that makes them engines of innovation.

Specialization: As Matt Ridley points out, King Louis XIV of France had 498 people preparing his 40 dishes to choose from for his dinner. However, the average person living in a city today has far more. Instead of doing things for ourselves we all now specialize in a few skills that we offer to many.

Diversity: Charles Kuralt once remarked that New York wasn’t really a big city at all, but a bunch of small cities right next to each other. Every neighborhood has its own flavor. Jane Jacobs insisted that it was this diversity that was essential for the long term success of cities and proposed that urban policy be designed to promote it.

Interestingly, despite being the world’s most important financial center, New York bounced back much more quickly than manufacturing centers after the financial crises.

Exchange: Biologically, the function of sex is to recombine information. Our DNA mixes within our own bodies (through a process called meiosis) and then with someone else’s. This is what creates the incredible diversity of people, not only within populations, but even within families.

Richard Florida’s research shows that the same type of ongoing recombination and renewal is crucial for innovation.

Go to the campuses of innovative companies in Silicon Valley and the first thing that strikes you is how many places there are for people to mix, from volleyball courts to ping pong tables to internal cafes. In other words, lots of ideas for ideas to have sex.

And therein lies the lesson. We fell in love with Carrie Bradshaw not simply because of sex (although that never hurts), but because of the endless possibilities unleashed when DNA combines.

Greg Satell is a blogger and a consultant at the Americal online media Digital Tonto. You can read his blog entries at http://www.digitaltonto.com