The French company Bic makes three things: razors, cigarette lighters and its first and most famous line, ballpoint pens. It produces razors in different versions for men and women without anyone objecting. So – it concluded – why not produce a ballpoint pen specifically for women? The product, "designed to fit comfortably in a woman's hand", comes in an "attractive barrel design available in pink and purple". The product was less successful among customers than might be hoped, and commentators on the internet made merry with the company's idea of what women want from a pen. "Thank goodness someone has finally noticed that, for years, women have struggled with pen usage," one Amazon reviewer wrote. "What is the point of being allowed to vote, when ordinary pens have been just far too uncomfortable and downright heavy, to grasp in our teeny, tiny, porcelain hands?"

Bic is rather a fascinating company. Its flagship product, the Bic Cristal ballpoint pen, was produced after Baron Marcel Bich bought the European patent from its inventor, Laszlo Biro, in the late 1940s. The Bic Cristal (which you're not supposed to call a biro) brought the cost of a ballpoint pen down from £2 15s in 1946 to a tiny sum. The only changes that have been made to the pen since 1950 are the introduction of a hole in the cap in 1990, to guard against suffocation and, from 1961, the ball has been made from tungsten carbide. Also unchanging is the cost, amazingly; the current price on Amazon of £7.74 for 50 is less, in cash terms, than it cost in the early 1960s. In 1970, six million pens were sold daily; by 2005, 100 billion pens had been sold worldwide.

What an amazing object it is! But are we in the very last days of pen and ink? Is it not just the idea of pens for women that people are regarding with ridicule and amusement, but the idea of pens altogether? An online stationer, Docmail, commissioned a survey in June about the last time any of us wrote something by hand. It discovered that the average time since an adult wrote anything at all by hand was 41 days. One in three people surveyed said that they hadn't written anything by hand for at least six months. Two out of three said that the last thing they wrote was for their eyes only – a hastily scribbled note, a shopping list or a reminder.

What has replaced this? The text message, the email, the tweet, the typed Facebook update. The love letter, the postcard, the casual note left for friend, partner, children, parents, the handwritten diary are all much rarer than they were. I can't remember the last time I saw a student essay that had been written by hand, or got a letter by hand – a very few friends send postcards from holiday, or to say thank you for something. But mostly we use keyboards nowadays, even for the most intimate communications.

I've written a book about what handwriting means, called The Missing Ink, published next month. I started to wonder what we are going to lose when it disappears altogether from our lives, when pens for women, pens for men, pens for anyone start to become curious objects, rarely to be used. Writing the book, I talked to a number of people, just asking them what they felt about their handwriting. It was startling how many people started by saying they were "ashamed" of their handwriting. No one says they're ashamed of their wardrobe, or their conversation, or their gait. It is as if handwriting offers a direct path into someone's humanity.

For hundreds of years, observers have tried to codify the sense we have that a person's handwriting offers a way into a personality. It's an eccentric pseudo-science that doesn't stand up to close analysis. But surely, when we see the way a human being writes with a pen on paper, we know something more about him or her.

It seems absurd that a pen manufacturer would find it necessary to make a pen specifically for women. But we've all had the experience of seeing handwriting which we assume, without deep analysis, to be that of a woman, or that of a man. Writing by hand is personal, and can reveal a lot about our status, our age, sex, whether we are withdrawn or outgoing, confident or shy.

Handwriting is taught very little in schools these days. Many opponents of it argue that everything is going to be done on keyboards and pads in the future, so what's the point? It is required in schools of only five states of the United States, for instance.

There's no question that we are going to move ever more towards typing and texting. But handwriting is so bound in with our humanity that to lose it would be to lose any number of humane, valuable things. Do we really want to live in a world where love letters are always typed? Where the postcard from holiday is entirely replaced by the Facebook update? Not a communication from X to Y, with that special formation of an "e" that Y has always liked about X's writing, but something that looks just like any other communication, which can be copied and pasted without any consideration. To tell the truth, these days, X might not even know what his old friend Y's handwriting looks like.

The Bic company's pen for ladies has been mocked as antediluvian, not just in its idea of a target market, but as a technology. These days, everyone uses a laptop to write. In the world of laptop typing, there is no old or young, male or female, educated or simple, confident or quiet. You type a "p" and there it is, the same as anyone else's "p". But a sense of humanity's rich variety and complexity, expressed through ink on paper, is fast disappearing.

We make an effort to do other slow activities, because we think it's good for us – we cook at length and we go for walks in the country. Are we going to start deliberately writing by hand for the same reason? Or are we just going to watch this wonderful element of our individuality, our humanity, disappear for ever?