Life expectancy is like the weather: it changes from place to place. In Japan, it's 79 years for men and 86 years for women. In the Central African Republic, it's 44 for men and 47 for women. Luckily for us, Britain is much nearer Japan: 77 for men and 81 for women.
A long time ago, reaching your fiftieth birthday would have been a big achievement in Britain too. What changed? A lot of things. Medicine, for one. What doctors can do today would seem like magic to doctors of a century or two ago. But we also live in a safer and cleaner world. In the nineteenth century, people could be poisoned by their wallpaper, because manufacturers used unsafe chemicals in everyday items. The Thames in London once stank like an open sewer, because that is more or less what it was. But as the link between dirt and disease became more obvious, proper sewers were built and deadly diseases began to disappear. Strong laws were passed to protect the quality of food and manufactured goods.
Because we're exposed to less harm in our environment, we fall sick less often, stay healthier and live longer. Prevention is better than cure. We eat better now too and we understand the dangers of smoking and drinking too much. We're also more careful in our everyday lives. When cars were a new invention, they killed many more people than they do today, even though Britain had a much smaller population in those days. All of these things haven't just increased the length of our lives, they've increased their quality too.
These trends aren't going to stop. Life expectancy will continue to rise even as the average age of the population gets higher. Medicine will keep on advancing, offering new treatments for old diseases and allowing us to keep fit and active far beyond what was possible in the past. Life is longer and we're better able to enjoy it.