In most developed countries, people are living longer than ever before. The average life expectancy is now over seventy years. There could be soon be major breakthroughs in the treatment of degenerative diseases such as cancer, heart disease and Alzheimer's, which would raise life expectancy up into the eighties or beyond.
Minor repairs may be possible. An experimental technique that involves transplanting embryonic tissue into damaged areas of the brain is already being tried out, with mixed results. But even if it does become possible to repair and replace parts of the brain, such methods cannot restore memories. To preserve a person's identity, to preserve the self, any degeneration of the brain must be prevented. This means finding an answer to the fundamental question: why do we grow old and die?
The degeneration of cells and molecules may be the most fundamental cause of ageing. Cells can be seen as chemical factories, driven by incredibly complex reactions between hundreds of thousands of different molecules. The most important kinds of molecules are proteins and DNA. Proteins are precision tools which perform highly specific tasks. DNA molecules are the blueprints from which the proteins are made. If proteins are damaged or altered they may become useless. If DNA is damaged or mutated, proteins made from the mutated part will be useless. And both proteins and DNA are under constant assault every minute of every day. Radiation, ultraviolet light, viruses and toxins can all damage proteins or cause our DNA to mutate.
Fortunately evolution has prepared us for this onslaught. Proteins are constantly being broken down and replaced, and our cells have a number of mechanisms for repairing DNA, capable of carrying out thousands of repairs every second. But it is a losing battle - over the years, cells will inevitably accumulate damage. This can affect their ability to repair themselves, leading to a cycle of decline.
Mitochondria are rather unusual because they contain their own DNA, whereas all other DNA is found in the nucleus of the cell. But although mitochondria contain DNA, they lack most of the DNA repair mechanisms found in the nucleus. This means that most free radicals are produced where they can do the greatest damage, by attacking mitochondrial DNA, destroying the ability of mitochondria to produce energy and thus causing cells to grind to a halt.
We don't yet know whether free radical damage is the main cause of ageing but the evidence is growing. For example, it has been shown that the brains of older people contain a higher proportion of oxidised proteins, that mitochondrial DNA mutates far more rapidly than chromosomal DNA (in the nucleus) and that mitochondrial mutations play a role in various forms of degenerative diseases, including Parkinson's disease.
Drug companies are likely to pump more and more money into this area of research. The financial rewards for developing a successful anti-ageing treatment could be vast. There are lots of possibilities. For example, our bodies do have natural protective mechanisms against free radicals, and there may be ways of boosting their effectiveness. Gene therapy could be used to replace damaged genes or to add back-up copies of important genes. However even if free radicals are the main cause of ageing, they almost certainly aren't the only one; as we become better at preventing free radical damage, we may find that people start dying from other causes.
What does seem certain is that more ways, and more effective ways of slowing down the ageing process will be developed. This, along with other advances in medical science, means people will be able live longer in the future. The question is "How much longer?". And if the answer is "a lot longer", how will this affect society?
The growing proportion of elderly people in countries like the UK has already prompted some demographers to warn of an impending crisis. Will the rest of society be able to cope with the burden of caring for the elderly? Part of the problem is that while modern medicine can keep elderly people alive for much longer, it cannot restore their health, so leading to an ever increasing need for expensive medical care. Hopefully in the future medicine will not simply keep us alive, but will also keep us young. Octogenarians might be running around in teenage bodies. In which case they could look after themselves.
Violence should decline - most violent crimes are committed by people under twenty-five. Just about every study on the causes of crime points to childhood problems. If there were relatively fewer young people, more resources could be devoted to their education and to helping those with problems. The world could become a more mature, more thoughtful, more tolerant place. Maybe.
Finding out more about ageing
The following newsgroups discuss ageing:
You could also try searching for key terms. For example, "free radicals" should turn up a lot of info - most of it produced by companies advertising their products, so treat their claims with caution. If a miracle cure is ever invented, you'll hear about it.
Accumulation of damage
At least, this is one theory, sometimes called the wear and tear theory. The other main theory is that we are somehow programmed to die, that we have a self-destruct mechanism built into our bodies. But there is very little evidence to support this.
Can never be replaced
The brain is a staggeringly complex organ. It contains over 8 billion nerve cells, each of which may have a thousand to ten thousand connections with other nerve cells. Which means there are more possible ways to wire up our brains than there are atoms in the universe.
Mitochondria contain their own DNA
Why? It is now widely accepted that mitochondria were once free-living bacteria. At some time in the distant past these bacteria developed a symbiotic relationship with primitive cells, living and reproducing inside them. As these primitive cells evolved into multicellular organisms, mitochondria became an integral part of them but still retained some of their own DNA.
PBN
The work on PBN has been done by John Carney and colleagues at the University of Kentucky. Carney hopes clinical trials of a PBN-like drug will begin within the next two years.
Would raise life expectancy
Providing, of course, that infectious diseases remain under control. The rise in life expectancy in the developed countries during this century is largely due to the widespread use of antibiotics and vaccines. Unfortunately infectious diseases look set to increase again in the next century:
One of the less desirable consequences of the Human Genome Project is that it is rapidly closing this knowledge gap. The enthusiasm with which people have set about creating computer viruses does not bode well for the future. [Back]