Science & Technology: The Sceptical Inquirer - `Time Is Embedded in Our Genes, and Biological Clocks Are Found throughout All Living Organisms'
Wolpert, Lewis, The Independent (London, England)
I HAVE always been puzzled by what determines how much sleep we need. I have always slept a lot and believed I needed to, and I also suffer badly with jet lag. It is now clear that time is embedded in our genes, and that biological clocks are found throughout all living organisms - from bacteria through worms to humans. We live in a world of day and night and have had to adapt. As a result, we spend an average of 20 years of our lives sleeping.
At a large international meeting of neuroscientists, much of the discussion over coffee was whether those who were in a very different time zone to home could get over their jet lag by taking melatonin. There are recent studies suggesting that it can help. Melatonin is secreted by the pineal gland in the brain during darkness, and it sets the master body clock that we all have. This gland is located in a special part of the brain and controls our circadian - daily - rhythm.
This clock region has some 50,000 nerve cells and their genes are turned on and off in a complex manner to measure the passage of time. This clock can also control body temperature, which is at its highest at night and one degree lower after a good sleep.
While our clocks all run on a 24-hour cycle, they can affect our behaviour in quite different ways. Some of us - not me - are alert early in the morning, while others are best at night and go to bed very late. The historian Roy Porter wrote more than 100 books in his life. When I asked him how he did it, he told me that he got up very early each morning and was at work by 5am.
When I asked how long he continued he was puzzled by the question - clearly most of the day. Had his genes combined to give him a special clock?
The elderly, it has been found, produce less melatonin and so experience more disturbed sleep. But if they are exposed to bright light during the middle of the day, their melatonin production is higher at night and they sleep much better.
A serious age-related sleep problem occurs with Alzheimer's disease, as some nerve cells are lost from the master clock. …