Appendix B:
The origin of the Zodiac

In Section 5, I explained the difference between the constellations of the Zodiac and the astrological “signs”, which share the same names, but no longer coincide. When astrology as we know it was first invented, around 2500 years ago, the “signs” of the Zodiac were named after the already existing constellations, with which they roughly coincided at that time.
Some of these constellations are believed to date back much further than that. While some of them represent characters and creatures from Greek mythology, it’s believed that the Greeks assigned their myths to existing star patterns, which were far older.
Some years ago, Aleksandr Gurshtein, a Russian historian of science, proposed an interesting theory as to when and why the twelve Zodiac constellations may have come to be invented4. To follow this, you need to understand the basics of the phenomenon of precession, which I’ve described briefly in Section 5.4, and in more detail in Appendix A.
The twelve Zodiac constellations lie along the Ecliptic, the apparent path of the Sun around the sky during the course of a year. The Ecliptic is in fact the projection of the Earth’s orbit onto the Celestial Sphere. ( According to the constellation boundaries defined by the International Astronomical Union, the Ecliptic actually passes through thirteen constellations – the “extra” one being Ophiuchus – but that’s irrelevant to this discussion. We’re concerned here with the traditional constellation patterns, not modern arbitrary boundaries. )
With a handful of exceptions ( e.g. Orion, which really does suggest a giant figure with a belt and sword, and Leo, which does sort of resemble a lion ), most of the traditional constellations bear little or no resemblance to the people or animals which they are supposed to represent – which suggests that their significance was symbolic, rather than pictorial. Some – such as Orion again, with several bright stars – do stand out as conspicuous and noteworthy patterns, but many don’t. In particular, several of the Zodiac constellations are actually pretty faint. Pisces, for example, covers a large area of sky, but contains no bright stars; in a light-polluted urban sky today, you would struggle to even see it. This suggests that the patterns were defined and named due to the importance of their positions, rather than their conspicuousness.
As I explained in Section 5.4, the Vernal Equinox moves slowly along the Ecliptic due to precession, going all the way around the circle in a period of 25800 years. Today, the Vernal Equinox is in the constellation of Pisces, but 2000 years ago, it was in Aries; 2400 years from now, it will be in Aquarius, and so on. Obviously, the Autumnal Equinox, and the Summer and Winter Solstices, which are located 90° apart around the Ecliptic, move similarly.
So for any one of the Zodiac constellations, there was a period in history or prehistory during which that constellation coincided with the Vernal Equinox, another period during which it coincided with the Summer Solstice, and so on. This is the basis of Gurshtein’s theory; he proposes that the twelve constellations originated in three groups of four, which served as “markers” of the seasons at three different “precessional epochs”.
Let’s start by listing the twelve constellations, in the order in which the Sun passes through them:

Aries, the Ram
Taurus, the Bull
Gemini, the Twins
Cancer, the Crab
Leo, the Lion
Virgo, the Virgin
Libra, the Scales or Balance
Scorpius, the Scorpion
Sagittarius, the Archer
Capricornus, the Goat or Sea-Goat
Aquarius, the Water Bearer
Pisces, the Fish

Gurshtein groups these into three interleaved groups of four – the first group consisting of the first, fourth, seventh and tenth constellations, the second group of the second, fifth, eighth and eleventh, and the third group of the third, sixth, ninth and twelfth. Hence we have:

The Aries Quartet   – Aries, Cancer, Libra, Capricornus
The Taurus Quartet – Taurus, Leo, Scorpius, Aquarius
The Gemini Quartet – Gemini, Virgo, Sagittarius, Pisces

For each of these quartets, it’s possible to find an epoch in history or prehistory, for which the four constellations of the group, in the order listed, more or less coincided with the Vernal Equinox, Summer Solstice, Autumnal Equinox and Winter Solstice – the positions of the Sun on the Ecliptic at the start of each season. Each quartet is named for the constellation which contained the Vernal Equinox at the relevant epoch. ( Obviously, when the Sun is in a particular constellation, that constellation can’t be seen – but the Sun’s position can be easily deduced, from the fact that the diametrically opposite constellation is highest in the sky at midnight. The locations of the equinoxes and solstices at any epoch could have been determined by observation, without the people of the time having any knowledge of precession. )
These epochs ( rounded to the nearest thousand years ), and the locations of the equinoxes and solstices in each, are as follows:

Epoch                  Spring      Summer      Autumn      Winter
6000-4000 BC    Gemini     Virgo          Sagittarius   Pisces
4000-2000 BC    Taurus      Leo            Scorpius    Aquarius
2000-1 BC          Aries        Cancer       Libra          Capricornus

So Gurshtein suggests that these three quartets of constellations were invented during those three epochs, roughly 2000 years apart, as markers of the seasons. ( Due to precession, the positions of the equinoxes and solstices change by, on average, one constellation per 2150 years. ) So the Gemini Quartet is the oldest, and the Aries Quartet the most recent. Libra, in the Aries Quartet, is known to have originated more recently than most, as many ancient texts depict it as the claws of Scorpius, before it became a separate constellation.
There are recurring themes in the symbolism of these constellations, which support the theory. Many ancient cultures saw the Sun’s annual motion around the sky as a cycle of birth, life and death. It reaches its highest in the sky at the Summer Solstice, and its lowest at the Winter Solstice; the latter was seen as its death, followed by its rebirth. In both the Gemini and Taurus Quartets, the symbols could be seen to represent a sequence of birth, life, degeneration and death – or ascent, height, descent and depth.
The epoch of the Gemini Quartet is prehistoric – the Neolithic or New Stone Age – so any ideas regarding the symbolism of the constellations is extremely speculative. Three of the constellations of this quartet differ from most of the Zodiac, in that they are human or part human, rather than animals. Twins were prominent symbols in many ancient cultures, and often a symbol of fertility. So Gemini could have been a symbol of new life and the spring revival of nature.
Virgo is believed to have originated from the Mother Goddess of ancient Middle East cultures. She was depicted not as a virgin, but as a pregnant woman, or a woman giving birth – an obvious symbol of fertility. Virgo in her present form is traditionally depicted holding an ear of wheat – another symbol of summer fertility.
Sagittarius, the autumn marker of this quartet, is portrayed as a hunter with a bow – either as a man riding a horse, or as a centaur, a mythical creature which is half man, half horse. It represents the autumn part of the cycle; the hunter shoots and wounds the Sun as it crosses the Ecliptic, and begins its descent into the underworld.
Another theme here is that each of the symbols is “dual” – the twins, the virgin and her ear of wheat, and the horse and rider or centaur.
Many ancient cultures imagined an ocean below the flat Earth, into which the Sun descended to its death in winter. Pisces would have served as a symbol of the waters of the underworld; the “duality” theme of the quartet would explain why Pisces is depicted as two fish, rather than one.
The epoch of the Taurus Quartet was that of the Sumerian, Babylonian and early Egyptian cultures, and the beginning of organised religions. Many of the idols and deities of this period were in the form of animals, rather than anthropomorphic. The supreme deity was now male, rather than female, so the ultimate symbol of male fertility, the bull, was used to represent spring.
Lions were also worshipped as a symbol of supreme power ( even today, the lion is the most important symbol in heraldry and coats of arms ), so Leo was an appropriate symbol for summer and the Sun’s highest point. Scorpius played the same role as Sagittarius had done previously - the scorpion now wounded the Sun in autumn – and winter was represented by Aquarius, another water symbol.
The epoch of the Aries Quartet was the era of the Old Testament, when monotheistic religions were taking over from the Sun gods and animal gods of earlier eras. Some of the symbols of this quartet may be connected with the art and literature of the time. The ram is of course another male fertility symbol, and was often connected with spring rituals in early historical cultures. Similarly, references to goats are found in many religions, including in the Old Testament. Capricornus, however is often depicted as a mythical creature, a goat with a fish’s tail – yet another water symbol for winter. Autumn is no longer represented by the wounding of the Sun, but Libra is an appropriate symbol for an equinox, denoting the balance of day and night.
The significance of the crab for summer isn’t clear – but in Egyptian art, Cancer is often portrayed not as a crab, but as a scarab, a creature of much significance in that culture.
It’s logical to assume that, generally speaking, the oldest constellations are likely to be the biggest, and the most recent ones the smallest, since the latter would have had to be formed within the gaps between the already existing patterns. Indeed, the “modern” constellations of the northern hemisphere, which were introduced in the Seventeenth Century, are mostly much smaller in area than most of the ancient ones. So if Gurshtein’s theory is correct, we would expect the constellations of the Gemini Quartet to be the biggest, and those of the Aries Quartet the smallest.
This is indeed the case. On average, the constellations of the Gemini Quartet each cover 890 square degrees of sky. Those of the Taurus Quartet are significantly smaller, with an average area of 805 square degrees – the difference being greater than any uncertainty due to the ambiguity of boundaries – and those of the Aries Quartet are very much smaller again, averaging only 475 square degrees. This correlation of sizes strongly supports Gurshtein’s theory, regarding their relative ages.
So, despite their later nonsensical association with astrology, the symbols of the Zodiac appear to have originated for much more sensible and practical reasons.


4. Aleksandr Gurshtein, When the Zodiac Climbed Into the Sky, Sky and Telescope, October 1995.

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