This year began with some thought-provoking news – in future, nearly one- in-five of us can expect to live beyond 100; infant mortality is declining in parts of Africa at a faster rate than it did in Europe, and fertility is now below the replacement rate in almost half the countries in the world.

On the face of it, some of this is very good news as there were only 2,600 UK centenarians in 1981, and it is expected to rise to 280,000 by 2050 – less than 40 years away. It’s on the way, as it was already 11,600 in 2009.

Indeed, you could be one of the lucky ones, as about three million under the age of 16, five million between 16 and 50, more than a million between 50 and 65, and almost one million more who have already retired could well reach the milestone age in due course.

Overall, it seems that better medical support and a more varied diet are keeping us alive for longer, despite the products of the fast food industry and a more sedentary lifestyle making us larger and more slothful. So what’s the problem?

In the past, it was assumed that we worked for about 50 years, producing wealth for society and a bit for ourselves, then retired for a short time and then made way for the younger ones.

There were always more fit working folk than the old retired ones, so providing pensions wasn’t too difficult, particularly as the men died earlier than the women – who were paid less anyway.

But all that is now changing, and we face a future with too many people, too many old ones, and too few to do all the work to keep the economy ticking over.

Less than a year from now, the world population will be more than seven billion, growing at the rate of 25 every ten seconds. It’s set to keep on growing, and the eight billion mark should be reached by 2026, just 15 years away.

We have few political answers to the questions that this rapid increase poses. We will need to grow the extra food, and find the extra energy that will be demanded, and both are likely to produce more CO2 and faster and more threatening climate change.

Most of the extra billion-plus won’t be born in Europe, Canada, Australia, the USA or Russia, but that is where they may wish to end up.

As the dominant mammals on the planet, we need to address the implications of having increased our numbers fourfold in less than a century.

The elephant in the room is an extra billion people.