For years, scientists believed that nearly 98% of our DNA was “junk”—useless remnants that didn’t code for any proteins. But over time, researchers discovered that this so-called “junk DNA” actually contains essential elements, including regulatory sequences that control when and how genes are expressed. In fact, it’s now understood that this non-coding DNA serves as a kind of instruction manual, allowing genes to respond to environmental cues, adjusting their activity based on the context in which they are triggered.
This insight has transformed genetics. Scientists like Robert Sapolsky even suggests asking “what does a gene do?” is almost meaningless. Instead, we should ask “what does a gene do in this particular context?”, because gene expression—and the traits that arise from it—depends heavily on the surrounding environment.
But what do our genomes have to do with the cities we live in? It turns out, quite a lot.
The City as a Manual for Human Behaviour
Just as genes operate within the context provided by regulatory DNA, human behaviour and identity operate within the context of our environments. Cities, for instance, aren’t just places we inhabit; they’re spaces that subtly, but powerfully, shape our actions, thoughts, and even our values. When we view cities as environments that co-create our behaviours, we see urban design as more than just a practical consideration. Instead, it becomes an active participant in shaping who we are and how we live.
Think about a city square. Traditionally, it might be designed for function—easy movement, good visibility, or high-density parking. But a square redesigned with human connection in mind—benches for lingering, green spaces for relaxation, and paths that encourage walking—does more than just serve a function. It invites social interaction, encourages active lifestyles, and fosters a sense of belonging. Like the non-coding DNA guiding gene activity, the layout and design of our cities guide our everyday choices and, ultimately, our community’s social norms.
Implications for Urban Design and Human Flourishing
Understanding the city as an active “manual” for human behaviour opens up profound possibilities for urban planning and public policy. By viewing the environment as a co-creator of behaviour, we can design cities that encourage positive social norms and well-being. Here are a few key implications:
1. Behavioural Health and Active Lifestyles
Just as environmental factors in our genome can promote health or susceptibility to disease, cities can foster physical and mental well-being through their design. Copenhagen’s Harbour Bath turned an industrial site into a recreational swimming area, integrating physical activity with public leisure space. Residents enjoy better physical health not because they’re told to exercise, but because the environment makes it a natural, enjoyable choice.
2. Social Connection and Community Engagement
Cities designed for social interaction help shift social norms toward community engagement and collective well-being. Take Millennium Park in Chicago, where open lawns, art installations, and performance areas naturally draw people together. Just as our genome’s non-coding regions fine-tune gene expression, these thoughtfully designed spaces foster a “social expression,” drawing out behaviours that strengthen community bonds and build collective identity.
3. Identity and Public Spaces
In the same way that genes are influenced by their surrounding DNA to “choose” specific paths of expression, our identities are shaped by the social and physical environments of our cities. Barcelona’s Superblocks, for example, limit car traffic in specific neighbourhoods, transforming streets into shared social spaces. This subtly shifts behaviours and social expectations: people move more slowly, interact with neighbours, and treat these spaces as an extension of their homes. Over time, this contributes to a sense of shared identity and community pride.
4. Sustainability and Natural Living
While sustainability goals are often presented as sacrifices (like taking fewer flights or using less energy), cities can design spaces where sustainable behaviours feel effortless. The High Line in New York, an elevated park built on a disused railway track, invites people to experience nature, enjoy scenic views, and walk instead of drive. Just as gene regulation allows an organism to adapt without conscious effort, the design of the High Line subtly encourages sustainable behaviours that feel enjoyable, not burdensome.
A New View of Urban Life
This perspective on cities—as manuals guiding human behaviour—encourages us to approach urban design with new sensitivity. Cities that integrate green spaces, encourage public gatherings, and support active lifestyles do more than improve functionality; they transform how we live and how we see ourselves within the community. Urban design becomes an intentional guide, a way to help people thrive rather than merely function.
Just as epigenetic markers tell genes how to respond to external cues, the elements of urban design tell us how to live in harmony with each other and our surroundings. When we recognise the environment’s active role in shaping behaviour, we can create cities that not only support well-being but foster human flourishing.
By viewing our cities as part of the “manual” for life—much like the non-coding DNA that guides our genes—we open up new possibilities for designing spaces that help people feel connected, supported, and inspired.