
Apparently something has happened (I don't know precisely what, but it may have to do with Ophiuchus and the precession of the equinoxes, which is old news to serious astrologers but who cares), and [EDIT: insulting phrase redacted] various sceptics have been popping up to point and laugh at the stupid people who believe inanimate balls of gas and rock know what you're going to have for breakfast next Tuesday, or something. [Paraphrase is a composite of various general comments on astrology from Terry Pratchett, David Langford and others, and does not refer to any specific comment on this issue.]
So I thought it would be a good time to re-run my speculative theory about the origin of astrology, which I arrived at using my special variant of Occam's Razor, in which you go with the simplest explanation that fits all the available facts and doesn't depend on everyone except you being a moron. Here goes, then:
1. The personality traits came first. Gazing into the sky and propitiating the gods is all very well, but I think it's been fairly well established that your successful king, general or merchant tended to be a pragmatist and was more likely to pay good money for something which would tell him useful information about his subjects, customers or enemies. The traits were not made up, they were observed.
2. Once they had been observed and codified, some form of classification would have been needed, and animals have always been linked in folklore to particular qualities of humans, so that would be a useful way to go. Some people are like bulls, some are like fish and so on. (I seem to remember being told that we went through various systems before arriving at the current zodiac, but I'm not sure what they were.)
3. This is where the stars come in. Looking for some way to explain the progression of animal-like traits they'd discovered, the ancient astronomers found that if they grouped the stars along the sun's path in a certain way and really used their imaginations, they could find the relevant animal shape in the position where the sun was at the moment of the person's birth. To be honest, I'm quite surprised they thought of this at all, since barring an eclipse it's kind of hard to see the stars immediately behind the sun. It doesn't seem intuitive, if you see what I mean. Nevertheless, think of it they did.
4. And this is where the gods come in. "Why is there a bull in the sky?" people would ask, after the relevant constellation had been pointed out to them ("No, there...well, try squinting a bit..."). And the ancient sages eventually came up with a story, which by the time the Greeks came along had been fully incorporated into the corpus of myth surrounding the tenants of Olympus. This explains the bittiness of the stories and the unlikely selection of bods who got asterised.
The beauty of this theory is that it's not in any way a defence of astrology itself. I personally believe there might be something in it, but it's just as likely that the original observations were flawed, that witnesses were inadvertently led, that cold reading techniques were employed. Humans are a diverse lot and don't fit easily into any number of boxes, so all that could ever have been observed and codified were broad tendencies which could have been illusory.
What it is, I think, is a right way round view of events which are commonly viewed in reverse; that the ancients, looking for ways in which the gods might have shaped the souls of humanity, decided the stars were full of creatures and then arbitrarily imposed their characteristics on people. Nothing within the history of science (as far as I know) has been decided that way, and it's not a very sensible way of going on whether you believe in gods or not. My way of looking at it has as much chance of being true as any other version, and it's a good deal kinder to our ancestors, to whom we owe a fair bit.
And it opens up the possibility that the progression of personality traits documented by ancient astrologers, if it exists, has absolutely nothing at all to do with the stars or the planets as such, but has some other cause which nobody has bothered to look for, because opinion is polarised between "it's true, and it's the stars" and "it isn't true at all because the stars explanation doesn't make sense." If that's so, it explains why the precession of the equinoxes hasn't affected the casting of birth charts in any significant way (till now, and if it does I think it will just mess things up for honest astrologers).
That said, if you want to pour scorn, go ahead. I have no proof to offer, nor any particular emotional investment in this issue, so be as sceptical as you like. And if you know something which knocks my theory into a cocked hat, do please share.