Last Updated Mar 24, 2010 7:45 AM EDT
The theory goes that testosterone production dampens immune defences - the male body can produce sperm, or defend itself against illness, not both. The more testosterone a man produces, the more it impacts on his immune system.
Women are naturally predisposed to men who produce high levels of testosterone as mates, because they are more likely to produce an offspring. These men are passing on their genes to future generations of men and so men are progressively becoming more sickly, the more manly they become.
Women, on the other hand, produce more oestrogen, which is considered to boost the immune system. Women who produce high levels of oestrogen are more likely to produce offspring, passing their genes on to future generations of women, resulting in womankind becoming more able to fight off illness as time progresses.
So, when a man has to take a day off work, lie on the sofa and watch daytime TV under a duvet, he is merely subject to the laws of natural selection, poor fellow. More than that, he should be considered quite a catch by the ladies.
When a female colleague comes down with illness and has to take a day off work, well she's either not as poorly as she's made out, or it's a case of bad genes isn't it?
According to the 2009 CIPD Absence Report, unscheduled days off cost the economy Â£17.3bn last year. Now we know that this is not due to stress, job dissatisfaction or just plain malingering, it's a normal condition of mankind.