What it measures isn't maleness or femaleness, but levels of testosterone in the uterine environment, and it's only an average, so all one can really say is that, if one has been exposed to high levels of testosterone during gestation, those particular bones will develop differently than they would have if testosterone exposure hadn't taken place.

Men are on average taller than women, but that doesn't mean that tall people are male, or that short people are female.

Men have, on average, shorter index fingers than their ring fingers, possibly an adaptation allowing them more control when picking their noses.

Women have, on average, either index and ring fingers that are the same length, or a slightly longer index finger than their ring finger, obviously to ensure that the moral corrections applied to men through wagging one's index finger are more visible ad promptly acted-upon.

A few studies have suggested that homosexual men may tend very slightly to follow the female norm, but other studies have shown no difference.

One study has suggested that some lesbian women may tend very slightly to follow the male norm, but others have shown no difference.

One study has shown that some transsexual men may have finger length ratios approximating those of women. Others have shown no correlation.

http://en.wikipedia.org/wiki/Digit_ratio

The difference is usually very small, and easily influenced by subconscious alteration of the way one holds one's hands, so most people without access to a good set of calipers find it fairly difficult to estimate what the ratio really is.

That being the case, the whole exercise is more like a parlour game than science, and one can make of it what you will, like the configuration of the lines and wrinkles on one's palm.

Here's a PopSci site that talks about it:

http://viewzone2.com/fingersx.html

It includes exaggerated artwork and diagrams, as well as edifying letters to the editor explaining why so and so is a great artist, and this and t'other is autistic.

On my own hands, my left hand has an index finger noticeably longer than my ring finger, and I have a machinist's caliper which verifies my casual observation. My right hand has ring and index fingers that look to be exactly the same, although measuring with calipers reveals that my index finger is very slightly shorter than my ring finger. This tells me exactly nothing in real life.

Well, except that the fact that I own a precision caliper is probably very revealing.

Chiromancy, on the other hand, tells me that I tend to let my intellect rule my heart, and that I'm emotionally stable, which is fairly accurate. My phrenological profile, on the other hand, is whack. My natal chart pleases me, but I'm not sure that any random chart wouldn't be just as pleasing, as they all seem rather vague and flattering.

Cheers,

Puddin'