My thoughts on the matter while I sip morning coffee.
Every night, before bed, I go outside for a little bit, usually just to relieve myself, and stare up at the night sky. Where we live, we have quite good night sky, being far away from any major cities.
Orion is easily one of the more noticeable constellations in the night sky, and the brightest star you can see - Sirius, is nearby enough to Orion. Those three close triple belt stars nearly in a straight line catch the human eye easily, as does the large rectangular frame of 4 stars (Bellatrix, Betelgeuse, Saiph, Rigel) some distance from these close triple stars that seems to outline the constellation, with Betelgeuse and Rigel being relative bright as well, and thus easy to spot. There are no significant starts of magnitude between the three stars of the belt and the 4 stars of the rectangular outline, so it appears as a large domineering pattern in the sky.
Not too far from this, we have another curiosity - the stars that are the horns of Taurus, forming another symbol that is easy to spot, a "V", with one star being quite bright and noticeable (Aldebaran, which was originally called Ad-dabaran "the follower").
The difference in angle relative to the plane of the 3 stars in the belt of Orion compared to the 4 starts that are the outline make it appear that Orion is "facing" Taurus, and the rotation of the earth imparts a movement to the night sky where it appears that Orion is moving across the sky after Taurus, or Taurus is running away from Orion.
If we talk about start magnitude, we notice that Betelgeuse, the brightest of the 4 stars surrounding Orion, and Aldebaran, the brightest of the "V" shaped horns in Taurus, line up with a cluster of fainter starts that are suspiciously close together just past the "V", and these are the Pleiades.
One can stare at the night sky and notice patterns easily. This pattern above is quite prominent, and there are other patterns too that are easily visible. Certain patterns are more visible during different seasons of the year, and it is in the middle of winter where Orion, Taurus, and the Pleiades are the highest in the sky, taking center stage, whereas in the summer months, they are near to the horizon at night, only seen before sunrise. These symbols show up at the end of summer, beginning of fall, predominate during winter, and slowly disappear in spring! The way Orion is seen to rise is also quite interesting - it is the three starts in the belt that protrude above the horizon, in a near vertical fashion, which is a whole other topic of interest that I can go into if people are interested.
No doubt ancient humans (or humanoids) attributed familiar explanations to patterns seen in the sky, that were culturally relevant to their time. My belief is that many of the patterns and symbols and attributions to the night sky far predate not just agriculture, but also writing and symbol making. Just as cultures borrowed ideas from other cultures, I think many of the zodiacal explanations are borrowed from Neanderthal man.
We have a predominant figure that is chasing a V, and behind that V is a grouping. This can very easily be understood as the celestial hunt - the hunter going after the bull, or perhaps in prior times any horned animal, as the bull is more of a concept that developed during agriculture and domestication. It could be an antelope. While more "modern" depiction of the constellation of Orion feature a bow, as if to capture the technology of weapons that existed at the time, the stars surrounding Orion, or the starts that are not those 3 in the belt and the 4 surrounding it, are all fairly low magnitude, and many different patterns could be drawn. Thus we have some older alternatives of Orion as carrying a club and holding a slain animal, holding a sword and a shield (which now stats to question whether the sword and shield of mars is really referring to mars after all), or even holding a sling that is wound up with the stone ready to be released. Some modern renditions of this in the occult can even be likened to a "double wand", which is another avenue to investigate.
While Taurus is depicted as generally facing Orion, this is a more modern rendition that fails to capture the chase, or the hunt, or the general direction of movement of the night sky. Unless it is being used to mean "the horned animal is attacking the hunter while retreating", which I do not believe it is, the way Taurus tends to be drawn represents a loss of understanding of the development of the symbols, but I believe that the idea that Taurus faces Orion is part of a later recoding of the symbol that became prominent during agricultural times as a borrowed understanding that was used to justify sacrificial practices, especially of the sacrifice of the bull. The older Arabic name for the prominent star in Taurus "the follower" signifies that it is following the Pleiades, like an animal in the herd that has wandered off and is now further behind them.
Finally, on to Pleiades. The common myth has them as the 7 sisters, even though only 6 stars are visible (more on this later). It is my believe that associating them with sisters, or more specifically maidens, virgins, unwed women, is again a modern invention, specifically occurring during a cultural era in which the basic tenets of patriarchy were already well laid out.
Extending the concept of the Hunter Orion chasing the Bull Taurus, and seeing now a smaller grouping that is in line with the bright stars at a distance, who are also moving way from Orion as the night sky moves. It is more natural, in my mind, for a pre agricultural and pre-patriarchic culture to view this grouping as many smaller bulls, or antelope, or whatever, at some distance. It is the herd at a distance, and one member of this herd, Taurus, is close, and that is the one being hunted.
There is another angle to quickly consider, and that is what the general understanding could have been to ancient man of the meaning of the "moving stars" or planets. Whatever it was, I think it is safe to say it represented some significance (as seen for example in much later cultures that associated these moving starts with gods), and in cases where these moving starts moved through other more "fixed" patterns in the sky, these were further fleshed out into stories that carried significance. As Orion / Taurus /Pleiades are on or near the plane of the ecliptic, the movements of the planets through these symbols were often used to further imbue meanings into the stories.
We must ask, why is there this pervasive concept of calling the Pleiades 7, when we only see 6 stars? The Greeks knew the connection to Orion quite well, attributing the sisters to being the virgin nymphs companions to Artemis, goddess of the hunt, and explained away the fact that there were only 6 starts visible, instead of 7, by having one of the nymphs marry Sisyphus, and thus becoming mortal, and no longer displayed in the night sky. This cultural explanation worked for the Greeks, but failed to explain away why they inherited a myth involving 7 stars when only 6 were visible. On the topic of Artemis though, we have a very interesting connection to alchemy, which I think is worth spending time meditating on. Artemis is Diana, perhaps a symbol for our "salt", and even the Pleiades themselves rise and fall during times that very nicely align with not only the harvest season, but the season for sowing of seeds, which further beckons us to consider the symbols of Saturn in association with all of this. The Arabs called the Pleiades ath-thuraya, and it was part of a much larger constellation that depicted a woman arched over the sky, (hints of Egyptian arched Nuit here), with the star cluster associated with rain, no doubt because when it set just before dawn signified the start of the rainy season.
Back to the 6 vs 7. No doubt the ancients that observed Pleiades saw 7 stars. Today we see 6. Astronomers know that one of the stars, Pleione, in the cluster is visible using telescopes, but even that star itself undergoes variations in luminosity on a cycle of approximately every 70 years, and it is quite close to one of the other starts in the cluster that has much higher luminosity, but this was not necessarily the case if you go back far enough in time.
Pleiades is a cluster of stars, all born out of the same nebular cloud sometime on a sunny September afternoon approximately 100 million years ago, or roughly during the cretaceous period, which also responsible for the very best chalks you can find on various shore cliff faces. As these stars formed in the Pleiades nebula, their relatively close proximity to each other means they gravitationally influence each other, and thus the nebula, over time, is bound to dissipate, with the stars slingshotting each other as they disturb their complex orbits, and in 250 million years, there will no longer be a recognizable cluster of stars there.
Now Pleione, which as that 70 year or so fluctuation in luminosity, is also close to another star in the system, Atlas, and the star was named only as Atlas in 2016, in commemoration of the Greek myths (Atlas was the father of the 7 sisters).
Pleione and Atlas are part of a binary start system within the cluster, with Pleione itself rotating so quickly around itself that it become elongated, and this form part of that 70 year fluctuation in luminosity as it tends to elongate enough to throw off part of it's shell. Pleione is not visible with the naked eye, we only see Atlas which is much larger and brighter. A Meleg had made an animation of the movements of all the various stars in the Pleiades cluster (approximately 3000 stars) to show their movements from approximately 200,000 years ago ago until approximately 200,000 years from now, and it shows that Pleione and Atlas would have had a larger separation the further back in time you go, seeming to nearly overlap around 83,000 years ago.
I think then the myth of the 7 sisters being 7, and not 6, is at least as old as 83,000 years, and likely quite a bit older.
If we look at some other evidence, such as both the Aboriginals of Australia and the Europeans both having this myth, we can investigate the spread of haplogroups and see that the C4 aboriginal haplogroup would have split with the haplogroups of the Proto-Indo-Europeans out of haplogroup CF, approximately in the region of modern day southern Iran around 60,000 years ago. This brings much more questions than answers really, but point to how old this myth is, and perhaps it is the oldest of the myths that have survived.
If we follow this myth forward from there on, we find some of the earliest creations myths as well that have been captured in many distance sources that detail the creation of the earth from the remains of a slain heavenly cow, or sometimes the cow is then replaced by another symbol to re-encode, such as the Norse Ymir.
Sorry for the long typing - my morning coffee turned into 3. There is so much more to explore in all of this - I really do believe that investigating Pleiades opens one of the doors to understanding the whole system of symbolisms that have been captured in so many different ways. It is no surprise that the symbolism is prevalent in many cultures but also in architecture. Just as the original templars encoded hidden knowledge in their cathedrals, so too do some more modern cities encode hidden knowledge in their layout.