Could your birthday predict your fate? Yes, to some small extent:
The most obvious effects concern school grades — children born in at the end of the school year perform slightly worse than those born in the beginning, although the differences tend to peter out over the years. But there are other, more startling patterns that are not so easily explained.
In the late 90s, for instance, Leonid Gavrilov at the University of Chicago found that people born in the autumn tend to live longer. He has since confirmed the discovery with many different studies, looking at centenarians, his latest paper found that autumn babies are about 40% more likely to live to 100 than people born in March.
Gavrilov’s discoveries initially met with resistance and misunderstanding. “People who are not familiar with the most recent scientific studies on this topic remain sceptical, associating the work with astrology,” he says. “But when we submit our findings to peer-reviewed professional journals, they are now very well received by experts.” Sreeram Ramagopalan, at the University of Oxford, agrees that the field is gaining momentum. He points out that some of the earlier studies had only examined a small number of participants — meaning it was hard to be sure that the results weren’t simply a fluke. “Only very recently, in the last four or five years, have large studies addressed those issues comprehensively,” he says. Some of the recent findings come from tens of thousands of participants. Ramagopalan’s own studies, for instance, looked at the health records of nearly 60,000 patients in England, showing that winter and spring babies are typically more at risk of schizophrenia, depression and bipolar disorder.
Others traits influenced by your birth season appear to be your eyesight (winter babies are the least likely to be highly short-sighted) and your risk of allergies (people born in the summer are less susceptible).
Admittedly, the mechanisms behind these trends are a little murky. Changes in diet and yearly waves of infection could, feasibly, influence the growth of developing baby, with a lingering effect on its health for decades afterwards — even your talent at baseball could be affected (professional baseball players are more likely to have been born in autumn than in spring, possibly because they were healthier at the very start of their lives). You may also be exposed to different kinds of allergens during different seasons. Alternatively, it could be as simple as the length of the day. When it comes to eyesight, for instance, studies have shown that periods of darkness help to regulate the growth of the eyeball.
Check your hemispheric privilege! Enough with this hemispheronormative writing.