While I am one of the first to admit that the majority of astrology is pseudoscience, or at the very least protoscience, there is actually something to astrology. But it has nothing to do with the mysticism generally attributed to the practice.

It has nothing to do with the alignment of the stars or planets, or anything like that. But when you are born has a real world impact on your life. It was likely true even more so in the past. Let’s think about it. The first few years of development are very important for long term health. Malnutrition in youth, and also during gestation, can have long term consequences.

In “Fetal malnutrition and long-term outcomes,” Caroline HD Fall goes over a number of ways in which prenatal nutrition can influence long term health outcomes. And in the past, the distance between harvest season, as well as other related factors, could have a significant influence on prenatal nutrition.

The issue is that these factors are fairly local. After all, one half of the planet’s summer is the other half of the planet’s winter. But even still, it wouldn’t be surprising that, coupled with a desire to attach order to nature, that people would recognize similarities in health outcomes, and other related outcomes, based on when a person was born, and create a system which sought to improve their ability to predict the future.

These systems would also act as self fulfilling prophecies. Once people identify patters in groups of people, based on when they’re born, they’ll act in ways that will reinforce those patterns. It’s kind of like getting cursed. If you believed that you’re cursed, odds are you’ll start to make mistakes, you’ll focus on the negatives in your day, and so on. And if a person is burn in an unlucky month, and they believe it, they’ll start to be unlucky.

Evolutionary Dynamics of Culture

While some of astrology is just an attempt to impress order on an apparently unordered reality, the possible link between birth month and health outcomes may also be reinforced by evolutionary dynamics. Just like with biological systems, cultures evolve, and they are subject to natural selection. Traits which are beneficial to the culture, or at least allow the culture to persist and pass on those traits, tend to continue, while those that are harmful tend to die out. The recognition that there is a difference between health outcomes and related outcomes, by time of birth, could have helped those cultures prepare in ways that we’re not aware of.

Sources

Mary Regina Boland, Zachary Shahn, David Madigan, George Hripcsak & Nicholas P Tatonetti (2015). Birth month affects lifetime disease risk: a phenome-wide method. Journal of the American Medical Informatics Association, 22, 1042–1053.