This note is a part of my Zettelkasten. What is below might not be complete or accurate. It
is also likely to change often.
A system is Sustainable if it doesn't decline with time and change. But truly, no complex system can resist change and so when we say a system is sustainable, we mean that it changes so gradually in response to the environment that it is not apparent to the observer in real-time. Somewhat of a Ship of thesues scenario.
Culture is one such system, it adds more and more nuances and layers to the system which makes it more and more resilient as it ages. Every cultural change might not be adding to the resilience but due to Natural Selection, changes which boost the survivability and prosperity of a particular group will, over time, make that cultural change more prevalent. Things like Costly Signalling are retained because of this phenomenon and many cultural ideas degrade and are lost over time naturally. Its important to keep in mind that Old will likely outlast new in this regard.
As you zoom out and see more dimensions, the bigger system which contains a lot of smaller, more homogenous systems is more resilient than the ones it contains, put together (I cant prove this mathematically. It feels correct though). This is because diversity creates more possibilities and higher chance of survival through difficult circumstances.