Mientras más científicos estudian el desarrollo urbano, más se percatan de que las ciudades son como ninguna otra cosa en la naturaleza. Las interacciones sociales que ocurren en un entorno denso tienen un efecto multiplicador: crean más riqueza, generan mas y mas grandiosas ideas y edificios más grandes, aunque también pueden propagar más la enfermedad. En cierto punto, de maneras buenas y malas, la vida de la ciudad suma mucho más que la suma de vidas individuales de la ciudad.
El Instituto de Santa Fe, y su plantel de científicos incluyendo Geoffrey West y Luis Bettencourt, ha sido el hogar de muchas de estas introspecciones. Estos investigadores son ahora capaces de predecir varios beneficios socioeconómicos, como el PIB o la infraestructura vial, con precision sorprendente basados solamente en la población de una ciudad. La vida urbana, resulta que se conforma sorprendentemente bien a ecuaciones
Como investigador postdoctoral en el instituto, el antropólogo Scott Ortman recuerda haber pensado que los patrones sociales mostrados por las ciudades contemporáneas no parecía muy diferente de cómo se comportaron algunas civilizaciones más antiguas. Empezó a preguntarse si los principios que rigen estos patrones eran fundamentalmente los mismos a traves del tiempo o lugares.
“Lo que me di cuenta fue que los parámetros que estaban discutiendo como potencialmente capaces de explicar estos patrones no eran algo que fuera exclusivo a naciones contemporaneas capitalistas, democraticas, industrializadas,” dice Ortman, que está ahora en la Universidad de Colorado en Boulder. “Son propiedades mucho más básicas de presumiblemente cualquier sociedad humana en cualquier parte”.
“Hay una razon por la que hoy la poblacion humana se urbaniza rapidamente. Las ventajas intrinsecas en la mayor escala de organizacion social.”
In a paper released today in Science Advances, Ortman and collaborators (including Bettencourt) report what they call “striking and exciting” new evidence supporting just that hunch. The researchers report that productivity was greater in large ancient cities just as it is in dense urban areas today—though the nature of that production was monument and building size, rather than modern economic measures like GDP.
The work supports the basic idea of cities as great “social reactors.” In dense places, communal assets set in close proximity (such as food gathering or transport networks) free up people to direct energy in more beneficial directions (such as labor coordination or knowledge specialization). Highly dispersed places, where social connections are farther apart, don’t reap the same productivity gains.
“One thing that really strikes me is that this research suggests that humans—human groups—do generally benefit from coordinating their behavior at larger scales,” says Ortman. “In a sense, there’s a reason why the human population is rapidly urbanizing today. This work suggests that overall there really are intrinsic advantages to larger scales of social organization.”
Bigger Cities Build Bigger Civic Monuments
The researchers drew their conclusions from a close analysis of archaeological survey data on about 4,000 pre-Hispanic settlements in the Basin of Mexico that date from ancient times through the end of the Aztec era in the 16th century. Among other things, the surveys documented the size, shape, and general measures of all sorts of buildings from these settlements. These included the likes of civic monuments as well as individual homes.
Such details gave Ortman and collaborators an impressive window into urban life from much earlier times. They first looked specifically at the size and volume of monuments in these settlements, with the idea that such buildings reflect productivity of a city—a sort of ancient proxy to modern GDP. If social interactions truly enhanced urban life in a universal way, they would expect to see monument size increase with city size, just as GDP does in urban areas today.
Indeed, they found just that. The chart below shows that monument size (the solid line) grew at a “super-linear scale” in big cities—in other words, faster than the population growth rate (the dotted line). Larger groups of urban laborers built bigger monuments than smaller groups, and built them faster. The researchers attribute the boost in productivity to the collective power of social networks in these cities, given the limited technological advances identified over this period.
“What [the results] do suggest is that essentially there is a functional reason why urbanization in general improves the overall material well-being of humanity,” says Ortman. “It reduces the amount of resources needed per person and it increases the amount that’s produced per person.”
And Bigger Individual Homes, Too
The researchers also analyzed individual home sizes, using archaeological data on floor areas of palaces as well as more ordinary houses. They reasoned that as people in these settlements accumulated more material wealth, they also likely acquired additional possessions, which in turn would lead them to build bigger residences. Just as monument size served as a proxy for social productivity, home size was a proxy for personal productivity.
Once again, as the chart below shows, they found evidence of super-linear scaling in big cities. Individual homes were larger, on average, in cities that were more populated—suggesting that urban social networks multiply productivity (and thus wealth) at a personal level, too. By aggregating in one dense place, these ancient people were able to “balance the costs of moving within the settlement with the benefits of the resulting social interactions,” just as efficient big cities do today.
“These settlements of the Aztecs, which is the last civilization of this period we’re studying, seem to express similar things to what we see in modern cities,” says Bettencourt. “Even though they’re about what these societies did, like building monuments and houses, rather than putting money in the bank.”
That’s not to say this increased wealth was distributed evenly. The researchers found the top 10 percent of households made up 40 to 50 percent of the housing area—a statistic they call comparable to levels of income disparity found in the United States today. Ortman says that finding raises the question of whether or not it’s really possible to develop a big-scale urban society that shares household wealth equally.
“It doesn’t look like ancient Mexico figured out how to accomplish that,” he says.
The Digital Age Won’t Change Things—Yet
Bettencourt says he’s encouraged that social networks in different times and spaces organized themselves according to some general patterns. But despite these continuities, he stops short of concluding that all cities have operated the same way across all ages. He’d still like to see how things played out in other systems—especially in places where people produced their own food.
He suspects researchers will find a continuum of urban development based on how (and to what degree) cities provide residents with food, either through markets or central authority. Once food gathering is organized in a collective manner, he says, individuals no longer have to devote as much energy to obtaining it. Cities that take this step seem to cross an important threshold toward the creation of denser environments that facilitate productivity gains.
“We’re trying to understand some of these interesting patterns of potentially different kinds of urbanism that happened throughout history,” he says.
Another big question raised by this line of research is when—or whether—digital social networks will change the way cities develop in the future. Ortman doubts we’ll see much of a shift so long as food needs to be physically transported into a city, and into a home, and into a mouth. Until then, he says, distance will remain a limiting factor in what people can accomplish in a given day.
“When we have the ability to send food via WiFi, or send calories via fiber optic cable, then we’ll really be in a new world,” he says.
*CORRECTION: An earlier version of this post included an image of the Aztec Ruins in New Mexico, not a settlement in the pre-Hispanic Basin of Mexico.