Published online 4 April 2008 | Nature | doi:10.1038/news.2008.731

Column: Muse

Astrology's myopia

Seasonal effects on birth physiology inevitably raise spectres of astrology. But that's just irrational nonsense, says Philip Ball.

This week came the latest in a string of studies showing that the season of our birth may indeed affect who we are — a bit. Near-sightedness, or myopia, seems to be more common in babies born in the summer than in the winter1.

Other recent findings of this kind include reports of seasonal effects in fingerprint patterns2 and in gestation length and birthweight3,4.

Although links between physiology and the season seem odd at first glance, there are often plausible reasons for them. For example, expression of our genes may depend on conditions in the womb, which are affected by hormones and diet. These in turn are potentially influenced by seasonal weather or food availability.

The seasonality of myopia is explicable in view of evidence that exposure to strong light both before and shortly after birth affects the ability of the eye to focus properly. The seasonal birth effect, identified by Yossi Mandel of the Israel Defence Force Medical Corps in Ramat-Gan and colleagues, is small, and seems to kick in only for moderate-to-severe cases of myopia, which are probably preconditioned by a genetic susceptibility.

So far, so plausible. But you know what I’m thinking? How long before this is touted as ‘further’ evidence that there is something to astrology after all — that the celestial configuration can imprint itself on our bodies and minds?

With a sense of resigned dismay, we can expect this result to be added to the growing list of scientific findings, which so far includes sunspot cycles, animal navigation, solar-terrestrial climate correlations and even Gaia theory, that some astrologers have presented as evidence that science not only supports astrology but that it is also trying to appropriate its key ideas.

Mars ascendant

This isn’t the kind of thing one can nip in the bud, and I don’t delude myself otherwise. Let me say simply that all these July-born Cancerians whose poor vision has no doubt made them bespectacled introverts were presumably born in the Northern Hemisphere, since one must anticipate that the myopia effect appears in January in the antipodes.

No, I think it is perhaps more edifying to consider why astrologers want to draw solace from science at all. Most notoriously, they cite the statistical studies of French psychologist Michel Gauquelin, who claimed to show in the 1950s that more successful sportspeople and athletes were born when Mars was “rising or culminating” — just as you might expect for the ‘warrior’ zodiacal sign, after all.

This ‘Mars effect’ has been echoed in a recent claim that English football-league players are more likely to be born between September and November than any other time of year. (Sceptics might wonder whether the fact that those birth months make British boys older and thus often bigger than their school peers has anything to do with it.)

Actually, Gauquelin himself called horoscopes an “exploitation of public credulity”. But his research was extolled by the British astronomer Percy Seymour, who has argued in several books (most recently The Scientific Proof of Astrology; Quantum, 2004) that the configurations of the planets, Moon and Sun can leave an imprint on us via their magnetic fields.

I could point out that a fridge generates a stronger magnetic field inside your average household than Jupiter does, or that there is not the slightest reason to believe that exposure to magnetic fields can alter an infant's personality, but I’m not going to preach to the choir.

Seemed sensible at the time

Reading the signs: astrology was once based on 'reasonable' beliefs of the time. No more.GETTY

In any case, there is a more interesting angle on this issue, which is that one cannot simultaneously allow astrology its proper place in the history of thought and still believe in it today.

To say (as many scientists might) that astrology has always been nonsense is to say something more or less without meaning. No one can reasonably say that aristotelian science was nonsense; it was a best guess that proved to be wrong. The same is true of astrology.

Astrology is based on two principles: a correspondence between the macrocosm and the microcosm (“As above, so below”), and on the action of ‘hidden’ (occult) forces. The latter seems a perfectly valid assumption for the times, given that there was nothing to ‘see’ that explained magnetism or gravitation, for example. The former — the idea that events in the heavens governed those on Earth — was part of a long tradition, dating back at least as far as Babylonia, for which the tides and the seasons supplied corroboration.

Yes, the tradition was mistaken, but not unmotivated. Certainly, it is a whole lot less arbitrary than the methods of modern astrologers, who have allowed the whims of an astronomical nomenclature committee to determine the astrological virtues of at least one new-found planet-like body. The planetoid Chiron, discovered in 1977, was named after a mythical centaur renowned for skill at healing. As a result it is now associated with healing in astrology.

How does that work, then?

One forfeits the right to claim any justification for these ancient beliefs in modern science if one does not accept what those scientific explanations rule out too. When astrologers say (as one did apropos of Seymour’s work) that the Moon affects the oceans and so why not our predominantly watery bodies, they are in effect disqualifying themselves from using gravity as an explanatory mechanism: they miss the fact that gravity can explain the tides, but cannot explain an influence on smaller bodies of water, such as people (just do the sums).

More seriously, astrologers who seize on the latest scientific findings — whether of summer-induced myopia or seasonality of sporting prowess — as proof of their beliefs are like theologians hunting for God in dark energy: they misunderstand how those beliefs fit into the history of ideas. Astrology ‘worked’ when embedded in ancient and medieval cosmologies, which were not scientific but metaphysical.

The only meaningful point of scientific continuity between historical and contemporary astrology is not about finding new physical mechanisms for how it ‘works’, but about asking whether the psychological motivations for such convictions — most probably, a need to find meaning in and control of one’s life — remain the same. That's the more interesting question.

Astrology also endures, according to social critic Theodore Roszak, because of the inspirational appeal of its rich, venerable imagery. “It has poetry and philosophy built into it”, he says. He’s right about that. All it lacks is veracity. 

  • References

    1. Mandel, Y. et al. Ophthalmology 115, 686-692 (2008). | Article | PubMed |
    2. Kahn, H. S. et al. Am. J. Hum. Biol. 20, 59-65 (2008). | Article | PubMed |
    3. Davis, G. H., Dodds, K. G., Moore, G. H. & Bruce, G. D. Anim. Reprod. Sci. 46, 297-303 (1997). | Article | PubMed | ChemPort |
    4. Jenkinson, C. M. C., Peterson, S. W., Mackenzie, D. D. S., McDonald, M. F. & McCutcheon, S. N. N. Z. J. Agric. Res. 38, 337-345 (1995).
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