Of What Good is Migraine?
Headache roams over the desert
Blowing like the wind
Flashing like lightning
It is loosed above and below.
Flashing like a heavenly star
It comes like the dew
It stands hostile against the wayfarer
Scorching him like the day.
It has struck him
And like one with heart disease, he staggers
Like one without reason he is broken
Like one thrown in the fire
He is shriveled
Headache is like the dread windstorm
No one knows its course
No one knows its full time or its bond.
These words were carved on tablets in Mesopotamia over 3,000 years ago. The author’s identity is unknown, but can there be any doubt what the words are meant to describe? Migraineurs know all too well the unpredictability of migraine (No one knows its course) and its capacity to disable (like one without reason he is broken). Many of the 20 to 25% of migraineurs who experience visual aura can appreciate the description: Flashing like lightening … Flashing like a heavenly star.
Over 3,000 years! How has migraine, the "dread windstorm", persisted so long? Why has the process of natural selection not excised this particular portion of the human genome? Of what earthly good can migraine be to the individuals afflicted or to the community at large? As many as 12% of the general population is actively afflicted with the disorder. Why?
One simple answer might be that not enough time yet has passed for migraine to be selected out by the socio-biologic process we have characterized as evolution. But this seems unlikely. The evolutionary biologists of Darwin's era believed species modification via natural selection was a phenomenon that progressed at glacier-like speed, requiring many generations for, say, a given species of finch on a Galapagos island to experience a change in the color of its plumage as an adaptive response to its environment. We now know that natural selection can move along at a far brisker pace.
So that leaves open the question: why should a disorder that can cause such misery at often unpredictable intervals and even render one temporarily incapacitated, vulnerable, and largely defenseless endure for hundreds of generations? Can it be that migraine somehow is beneficial? If so, how could permitting the persistence of migraine, biologically speaking, provide any natural advantage? Does the persistence of migraine in some way benefit the human species?
Some argue that the intermittent nature of migraine and the symptoms it produces are not sufficiently harmful to require genetic pruning. After all, If the primary purpose of any species is to ensure its own propagation and it is this need to propagate that drives natural selection, there is nothing about migraine that would seem to inhibit procreation and propagation. Forget the old “Not tonight” jokes; migraineurs are at least as libidinous and sexually active as non-migraineurs. Migraineurs meet, mate and propagate just like everyone else.
But maybe, just maybe, there’s more to it than that. Maybe migraine does convey some natural advantage. Those with migraine are “blessed" with sensitive brains… brains that react differently than non-migraineur brains to weather changes, seasonal changes, hormonal changes, odors and a plethora of other internal and external environmental stimuli. Perhaps it was advantageous for a small tribe of Lakota Sioux living as nomads on the plains of the American West to have amongst them an individual who could sense before others that the weather was about to change, the buffalo were about to move, etc.
But we are not Lakota Sioux. Our environment and needs are not matched to the Great Plains of the nomadic tribes, and it is more difficult to conjecture how a “sensitive” migrainous brain would convey any advantage. While the prevalence of migraine does not appear to be decreasing, perhaps it is simply too early. Perhaps more than ten generations are required to kick migraine off the human evolutionary bus, and at some point in the future the current 12% prevalence will begin to shrink towards extinction.
So how about it? Is migraine disadvantageous to human society and simply taking its time to be selected out and eliminated? or is it so irrelevant to propagation and survival of the human species that it simply will endure indefinitely as a common genetic variation, much like blue eyes? or by its presence does migraine somehow convey a natural advantage to the community, enabling its members to more effectively get on with the business of procreation? While none of us is likely to live long enough to see the mystery of migraine’s persistence finally revealed, as a migraineur I prefer to live with the consolation that my episodic headaches and aura symptoms possibly may be good for something after all. Not a blessing precisely, but not entirely a curse.