Migraine – a remnant of human history?

We have known for several years that migraine – or rather, the predisposition to develop migraine – is influenced, among other things, by a range of genes within the human genetic make-up. Like all our genes, they are subject to constant change. Traits which prove to be a disadvantage are removed from our genetic material sooner or later, while the advantageous ones remain. In this way, living creatures – including us humans – are constantly adapting to the environment in which they live.

People with migraine will undoubtedly agree that this illness brings them significant disadvantages. From this perspective, the genes which are responsible for it should in fact have been removed from our genetic material over the course of human development. However, this is evidently not the case.

This means that there must be reasons why the predisposition to migraine has been preserved and is still passed on to our descendants. We will consider several of these in our article.

Why did the ‘migraine genes’ survive in human history?

Scientists have often given this fundamental consideration. The central question is: why do genes which cause susceptibility to severe headaches continue to exist?

We can get closer to answering this riddle if we look at it from a different angle. The question is now: can a gene which is clearly disadvantageous, because it causes pain, still be beneficial to its carrier because it is accompanied by a further quality which provides a considerable, possibly vital advantage?

This could then explain why the migraine genes have, to this day, not been removed from the human genetic material. But what qualities could these be?

A ‘cost benefit analysis’: looking after the brain, and migraine suffering

One possible explanatory approach relates to supplying our most important organ – the brain – with oxygen and energy. Normally, our body takes care of this without us even noticing – as it does with many other bodily functions. This can become dangerous if, one day, this control system does not run seamlessly, and our brain is at risk of becoming undersupplied. In this kind of potentially life-threatening situation, the nerve cells release vasodilators in a matter of seconds. As a result, the large blood vessels, which supply the brain with blood, widen. This prevents the impending shortage and ensures that the brain remains well-supplied. This lifesaving mechanism functions particularly effectively in people with migraine. The flipside : according to current scientific understanding, the most important messenger substance that is involved in this process is also suspected of playing a causal role in the development of migraine.

The particular ability to quickly widen the blood vessels in the brain is undoubtedly valuable – in an emergency, it can prevent supply shortfalls in the brain, thereby ensuring survival. The “price” of such a valuable advantage would then be the migraine, which develops as a kind of “side effect”. It seems as though, in a cost benefit analysis, a considerable advantage (survival when faced with an impending circulatory disturbance) is being gained in exchange for a comparatively small disadvantage (the migraine).However, the following always applies: the central nervous system of people with a predisposition to migraine is characterised by a fast processing speed for all types of signals.

Sensitivity to smell as an advantage?

Migraine patients frequently exhibit a particular sensitivity, sometimes even an outright aversion, to smells. This observation prompted scientists to speculate the following: in the early days of human development, this trait may have proven useful. This is because it also hinders or even completely prevents poisonous substances which are ingested through the nose from entering our olfactory organ and therefore our body. This is important because the olfactory nerve is the only sensory nerve which is directly connected to the brain. Dangerous substances which enter through the nose therefore have immediate access to our central nervous system. This could potentially pose major risks for the organism.

A distinct aversion to certain odorous substances could therefore have been very advantageous in human development because it kept the affected people’s brains from becoming damaged. This would undoubtedly be a valuable benefit, in exchange for which nature would accept the “small” drawback of susceptibility to migraine.

An old predisposition meets a modern living environment

The nervous systems of people with migraine have several specific characteristics. They are particularly sensitive to all kinds of incoming information from their environment and are characterised by a fast processing speed for all kinds of perceptions. In this way, affected people might for example perceive odours, light, or sound more strongly than people without the predisposition to migraine. Their pain threshold is also lowered. In addition, regularity when it comes to eating, drinking, and sleeping is of great importance. This means that, for example, skipping meals or an irregular sleep rhythm has a particularly severe effect on affected people. Resilience when faced with stress is also reduced.

Now, our modern living environment seems to present a particular challenge for people with these predispositions: overstimulation, the hectic pace of everyday life, sleeping problems, irregular eating. All of these are classic, known triggers for migraine. And, these days, we are undoubtedly confronted with them much more frequently than was ever the case during the long period of human development.

This is consistent with the observation that migraine frequency on the whole is increasing. It is possible that the effects of the predisposition to migraine, which has already existed in humans for a very long time, are simply greater today because the triggers are more prevalent. Perhaps we have always had migraine in our genes, but have only realised in the last few centuries that it can manifest in such painful ways.

In conclusion: nature’s bill (still) works out

As an illness, migraine could be the result of a ‘trade’ made by nature. Hereditary factors which, though burdensome, are not life-threatening – such as migraine – were potentially retained because they are accompanied by advantageous traits which are of overriding benefit. Ensuring blood flow to the brain or protection from poisonous substances – as described above – can prove to be vital and therefore highly valuable. This means that they outweigh the drawbacks which are associated with migraine as a ‘side effect’.

With everything that we currently know, it can be assumed that the inherited predisposition to migraine exists to this day because it continues to be acceptable in the ‘cost benefit analysis’ of nature. It comes with advantages which were particularly beneficial over the course of human development – and potentially still are to this day.

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