FASHIONS in hairstyles have changed over the years, as all of us “certain age” people have surely noticed.

Today’s prevalence of very long, very straight hair on women of all ages who are TV “regulars” aroused my curiosity about when and how this change came about.

I think of the 1940s, when females with naturally curly hair were to be envied. The rest of us had to spend the night in rollers, or figure out other ways to get the desired look.

Or we could get a “permanent,” the history of which dates back to a Frenchman named Marcel Grateau. He developed a process using heat to curl straight hair.

Then, around the turn of the 20th century, Karl Nessler invented a system that combined heat with chemistry, and required sitting under a cumbersome machine.

IDEAL BEAUTY Academy hosts a website titled Popular Hairstyles Over the Last 100 Years. It filled me in on the decades before I was born, and added interesting details about the more recent ones.

I learned that the transition from the fancy styles of the Victorian era into the first decade of the 20th century led to fuller, free-flowing hair. Regardless of the hair length, hair volume was the desirable trait in the early 1900s.

By the 1920s, longer hair was revered as the finest. But as time marched on the “flappers’” short bob haircut became increasingly admired — shifting the focus to hair accessories such as bows and clips.

IN THE 1930s there was a huge shift in hairstyles as the Great Depression took hold.

Women who couldn’t afford a beauty shop visit became more creative. Finger waves became very popular and there was an intense desire to be blonde like the Hollywood star Jean Harlow.

Glamour was the hallmark of 1940s hairstyles. Many of the most fashionable, highly feminine looks featured soft curls that took hours to achieve.

Jackie Kennedy and Lucille Ball were two celebrities who inspired many women in the 1950s. Big, backcombed bee-hives, bouffants, and the French pleat became the trendy style.

THE HIPPIE age of the 1960s evolved from “big hair” into a more relaxed, natural style.

The smooth, straight-haired look was what women wanted in the 1970s.

Girls had to take turns ironing each other’s hair, since the “straightener” had yet to be invented.

The popular hairstyles of the 1980s went “back to the future” in declaring that bigger was better. Ponytails on the side of the head, teased-to-the-heavens hair, and bangs were all trendy.

The 1990s ushered in a more relaxed look. By the end of the decade many women wanted shorter, looser, and layered hair, whether the style was up or down, informal or formal.

The Ideal Beauty Academy website asserts that 21st century hairstyles are driven by personal preference: “ Messy, waves/curls are seen as attractive as well as straight and refined. Hairstyles have plenty of room to experiment at this time because there doesn’t seem to be a certain style that women should stick to, rather an abundant amount of choices to consider.”

Let’s hope they’re right.