From “knocker-upper”, “milko”, paper boy, to human computers, there are dozens of everyday jobs that existed for centuries that have vanished from modern life.

My first job was as a 13-year-old spending four nights a week running up-and-down the streets of Mt Pritchard in Sydney’s south-west on my parent’s “milk run”.

“Two whites, a red, and a silver for No. 27,” my father would recite to me, denoting standard, homogenised, and low-fat varieties that were marked by the colour-coded aluminium caps on the one-pint (600ml) bottles that most people had their milk home-delivered in.

Milk runs, alas, like so many valued and important roles from the past, are one of the dozens of occupations that most people under 40 would barely know ever existed.

Imagine explaining to a teenager now, for instance, that people (“knocker-uppers”) were once paid to wake workers up by tapping on their bedroom windows with long sticks, pebbles, and pee-shooters?

Or that important messages would be delivered by hand from the post office by “Telegraph Boys”. How about hitting 15, and getting a job dragging a yellow wheel-barrow around your neighbourhood mornings and afternoons, incessantly peeling a whistle to let people know you had copies of all the major daily newspapers, as well as chocolate bars and other sweets for sale?

Or that thousands of people made a living manually connecting telephone calls, lighting street lamps, or performing calculations before computers existed.

In newspapers, trades such as copy boys, type-setters, linotype operators, paste-up artists, and proof-readers. Or how about a copy-taker, a sort of telephone receptionist, who a journalist would dictate their stories to remotely via a telephone… gone, all gone, all gone the way of the wheelwright and the street-sweeper.

Entire professions that once employed thousands of people and had their own guilds, unions, trade pride, and history, have disappeared in little more than a generation as technology transformed how people live, work, and communicate, Director of Operations at AnyBusiness.com.au, Mary Tamvakologos, said.

"Most people assume the jobs around them will always exist because they are familiar; history shows that is rarely the case,” Ms Tamvakologos explained.

"History is full of examples of successful businesses that disappeared because they believed customers would always behave the way they did yesterday,” she added.

The lesson, she emphasised, is that many of these careers — which were once considered stable, respectable professions with entire training programmes, businesses, and industries built around them — are now gone.

Most people born before 1990, for instance, would still remember how seemingly successful and universal Kodak film was. It was the preferred chemical film for millions of family happy snaps, professional photographers, and film-makers, while inventing the home movie and Kodachrome, the first colour movie format.

“What changed wasn't necessarily the underlying customer need; people still wanted information, entertainment, communication and convenience,” Ms Tamvakologos believes.

Technology simply created faster and more efficient ways to deliver them," she explained.

While many of the jobs on the list disappeared gradually, others collapsed surprisingly quickly as new technologies became mainstream.

The rise of streaming services rapidly reduced demand for video rental stores. Search engines largely replaced printed encyclopaedias.

Smartphones effectively combined the functions of alarm clocks, cameras, maps, calculators, music players and numerous other standalone products into a single device.

Ms Tamvakologos said that this lesson is just as relevant for today's business owners.

The companies that survive major shifts are usually the ones paying attention to how consumer habits are changing before those changes become obvious.

"One of the biggest mistakes businesses make is assuming current customer behaviour is permanent. Every business owner should occasionally ask themselves a simple question: If this business was launched for the first time today, would it look the same?”

With AI now threatening so many high-status, high-skilled while collar jobs ranging from accountancy to computer programming, she said that question is as relevant now, as it was in the past.

"If the answer is no, there is probably an opportunity hiding in that gap,” Ms Tamvakologos said.

“The businesses that endure tend to be the ones willing to adapt before they are forced to,” she concluded.

One last example, spare a thought for the “sano man” who travelled the streets of our towns late at night with a horse and cart up until the 1970s, picking-up the black-tar bins that people put-out their human waste in… that’s a job we can say, that we’re all glad to see the back of!