Time to take a look at our fair city. If you throw culture and economics into the mix, you find the city is more than diverse — it’s tribal. San Francisco is divided into dozens of neighborhoods and hundreds of groups, each with their own identity. [...] Palou in the Bayview is not that far from Third and Howard, but it is totally different, racially, socially and in every other way. The Castro Street folks and the Folsom Street types, the people who live in the past, like the hippies with gray ponytails, and the people who live in the present, like the surfers at Ocean Beach. There is a tribe in the Marina — “where the women are all young and beautiful and the men look like Gavin Newsom,” as one friend put it — and another on Valencia Street, hip and a bit scruffier. In the Latino Mission there are Mexicans and Central Americans, which are divided into subgroups with their own accents: Chinese are a majority in the Asian community, but there are also Vietnamese, Filipinos, Japanese, Koreans. Into this mix came the techies in waves — Like many before us, we went west in pursuit of a Gold Rush, a modern-day one fueled by the Internet,’’ wrote Mikkel Svane, a Dane who co-founded Zendesk. Look up “San Francisco Groups” on Facebook and there you will see the tribes: there are Excelsior, Mission, Richmond, Cole Valley and Sunset interest groups, among others. Even a site for members interested in Chinese lion dancers (1,967 members) and folks who went to a San Francisco Catholic school with 6,537 members of that tribe. Gentrification — essentially a sea change in the fabric of San Francisco — is the biggest ongoing story in the city.