The initial breakthrough - the one that made all this possible - came some years ago. You must remember: all that hype about the completion of the human genome project and then... nothing!

Well, there was something. Disappointment, as I recall, as the numbers quietly trickled out, smelling faintly of embarrassment. It was the usual anthropocentric thing. They assumed humans were so much more complicated than any other species that we must require many, many more genes. It was estimated that we'd have about 80 thousand. When the completion of the genome project was announced with great fanfare, they didn't mention straight away that they'd counted less than half that number - closer to 30 thousand. That is, about the same number of genes as a mouse. Plus a lot of what they called 'junk genes'. But never mind that. Now they'd be able to cure cancer and eventually everything else. Brilliant!

Years passed and every now and then there'd be a stir of excitement as some obscure scientist popped out of his laboratory to make a wild claim that ultimately proved to be a mistake or a 'fabrication'. So most of us forgot about it and got on with our lives. We got older and a lot of us got a bad back.

It was during one of my backache episodes that I started reading my son's science mag. There was an article arguing that most of the so called junk genes were nothing of the sort. Some had vital functions and others were just never switched on because, for example, we'd evolved beyond the need for gills or tails. It got me thinking. I remembered these words of wisdom from a favourite author:

"Many were increasingly of the opinion that they'd all made a big mistake in coming down from the trees in the first place. And some said that even the trees had been a bad move, and that no one should ever have left the oceans."

- Douglas Adams

- The Hitchhikers Guide to the Galaxy

Lying on that hard mattress, immobilised by a 'slipped disc', alternately high on opiates and poleaxed by pain, I tried to imagine how different my life could have been, if we'd stayed aloft. How wonderful it would feel to be swinging through the trees right now instead of lying here, helpless...

My son came home from school and demanded the return of his magazine. Only after I'd handed it back did he think to ask how I was feeling. I told him I wanted to throw away my digital watch and swing through the trees. He only laughed and asked if I'd like him to fetch me a banana.

Years passed. The back underwent operations. My son developed a little more sympathy when he too hurt his back. It was such a common complaint in those days, it seemed normal. Almost everyone I knew, above the age of 30, either had or had had back pain. I never entirely forgot my fantasy of an arboreal existence. I even had a recurring dream in which my prehensile tail and feet allowed me to fly like a bird through the trees. Talk about prophetic…

When it was first announced on the news that scientists had found, hidden amongst the junk, the section of DNA that would switch on tail genes, I didn't take much notice. It was only later, when I read about it in a respectable science journal, that I got excited. I wrote a letter addressed to the lab director. To begin with, they sent me a polite but firm refusal. They weren't yet ready to take that step and in any case, they thought I might be too old at 44. Also, of course, my lower spine was a mess of crushed discs. But I persisted and 18 months later they were ready - and short of healthy, young volunteers, so they relented. And that's how I became one of the first to undergo this form of genetic retro-engineering.

All it took was a few injections to switch on the ancestral genes - and some rather uncomfortable footling about at the base of my spine to introduce stem cells. The first signs of a tail were accompanied by a tremendous itching, but as it grew, my lower back pain disappeared and scans showed healthy bone and discs where there had previously been ugly scar tissue. After that, it didn't take very long for the tail to grow. It took a lot longer to learn to control it, but now I can swing by it - and even use it to open bottles.

It's surprisingly strong. My daughter says it looks horrible - hairless - like a rat's tail. That doesn't bother me though. I'm not vain. The important thing is that I no longer have back problems. My spine's been relieved of a duty for which is was never suited. And I love the tail. It's like having a third hand when I need one - or leg. I don't need stairs any more. Soon after I got the hang of using the new appendage, I had them modified so that I could fold them away and just let them down when guests come to stay. When a couple of youths tried to burgle the place a few years ago, they couldn't find any way up - and when I heard them crashing about, I got out of bed, unhitched one of my artificial lianas (the kind of rope you find in a school gymnasium) and sailed across hall, shrieking like and angry baboon. They practically flew out of the window they'd broken in through.

Things have moved on since the early days. Thousands of people have tails now - even young people who've not yet experienced back pain. It's all the rage - more popular than tattoos and body piercing. Most have fur on them these days. I saw the first on a very chic young woman in town some time ago. It was sleek, with black and golden rings, like a lemur's and she wore it stole-fashion: draped over her shoulder and coiled about her neck. And they've found other ancient switches too. My son, now a marine biologist living in Australia, loves diving but hates to be encumbered by diving equipment. He and his girlfriend have joined an already long waiting list to be genetically modified for an aquatic life-style. They're going to have gills. (Yet another excuse for not writing or phoning, I fear.) In future, sightings of mermaids and mermen will be an everyday occurrence.

Of course, we all appreciate the implications of this latest development. On land we're getting very overcrowded, whilst two thirds of the world is covered in ocean. This could be an answer to our overpopulation problem. And my son - and all those who take to the water - will make waves about how the world's oceans are abused by land-lubbers: those in the habit of using the sea as a cesspool, and the factory fishers that exploit species to the point of extinction.

My daughter, whose hobby is hang-gliding, wants wings. But that's not on the cards. There are no birds or flying mammals in our lineage. We just don't have those genes hiding in our junk. Just as well really. With our dense, solid bones and body fat - inherited from our 'aquatic ape' ancestors, I suppose - we'd never get air-borne.

Still, penguins do sort of fly through the water, don't they? Perhaps she'll consider gills.

They still haven't found the bit of DNA that would trigger the growth of prehensile feet. If they had, I would have thrown away my shoes and headed for a nice, warm jungle. I'm getting too old to make that adjustment now. But when it's found, some day soon I dare say, people will be heading for the trees - and forests will matter again.

The next invention I'm hoping for, is a way to keep our speciating species in close touch, so that we don't do what we always do when we've been separated for a few generation, and go to war.