Some examples: From NeuroEndocrinology Letters :
The vomeronasal organ (VNO), also termed Jacobson's organ, is a special part of the olfactory system(s) and can be found in most tetrapods at least in the embryonic stages. In most mammals, it is located above the hard palate on both sides of the nasal septum and consists of a pair of blind-ended tubes that open into the nasal cavity. In some mammals, it is connected to the oral cavity by the nasopalatine duct. Receptor cells in the epithelium of the mammalian VNO are not equipped with cilia [24, 25, 26] and their axons extend to an "accessory" olfactory bulb, that projects directly into the limbic system, bypassing the thalamus, and thus cortical integration. Simply put, the VNO is representative of an accessory olfactory system  that directly translates olfactory cues into neuroendocrine responses. In the past, the VNO was believed to exist only in lower mammals, and only at embryonic stages in primates. However, recent data have shown that the VNO also exists in adult humans . Monti-Bloch and Grosser  found the adult human VNO responds to picogram amounts of human skin pheromones with depolarization. These findings suggest, that the human VNO may function as a pheromone detector as it does in other mammals. However, so far there is no evidence that the human VNO is connected to a functional accessory olfactory system. This lack of evidence, in the past, has caused considerable scientific debate about whether or not there is such a thing as a human pheromone.
We don't consciously smell the pheremones, the attractive odours, of those we are sexually oriented towards. No, thus system bypasses our sense of smell, the chemicals hit the Jacobsen's organ, and instantly our brains get hit by neurotransmitters that start turning us on.
At one point on my peculiar metemorphosis, I was excuding both male and female pheremones, and responding to both. It was most confusing, and I'm very glad that is over. I definitely respond to male pheremones now.
But what about the nature of the response? I'm taking enough hormones now to feminise a football team, but serum oestrogen level is low. Does that mean my cellular receptors are binding to the oestrogen very well, or is my liver just re-processing it quickly? I think the former, but we'll have to see. One thing we do know about oestrogen levels is the way they effect women's choice in men. From the BBC :
Taking the contraceptive pill appears to change women's taste in men.Oops. When you can get pregnant, you tend to choose lousy fathers, when you can't get pregnant, you tend to choose good ones who may not be so exciting in the sack.
Psychologists have found that women who are taking the pill tend to fancy macho types with strong jaw lines and prominent cheekbones.
However, women who are not taking that form of contraception seem to be more likely to go for more sensitive types without traditionally masculine features.
Lead researcher Tony Little said: "Where a woman chooses her partner while she is on the pill, and then comes off it to have a child, she may find she is married to the wrong man."
The study found women on the pill appeared to make equally inappropriate choices when picking a man for a fling.
They were more likely to choose a "caring" man with feminine features.
Conversely, those not on the pill were more likely to choose a macho male for a fling.
Which might explain why I'm not attracted to Neanderthals. Well, I can't get preggers... and I'm taking the equivalent of 4 contraceptives a day....
If I ever do go to bed with a guy, a prospect I consider exceedingly unlikely, I'm afraid it will be because I love him. Sorry, much as intellectually I feel I should be more relaxed about sex, I'm not. I'm interested in possible Husband material only.
Psychologically, the fact that I can examine my own internal feelings and see that that is the problem causing my lack of interest in guys despite the chemistry, shows that little Zoe has come a long way. I thought there'd be a danger that I'd be boy-crazy, wanting to try out the new equipment and have enjoyable, natural, normal sex for the first time in my life. And that would be nice, I must admit.
Now I find I want love instead. Or as well as.
Maybe I should be around women who are breastfeeding more if I want a fling. From Science Daily :
Breastfeeding women and their infants produce a substance that increases sexual desire among other women, according to research at the University of Chicago.
"This is the first report in humans of a natural social chemosignal that increases sexual motivation," said Martha McClintock, the David Lee Shillinglaw Distinguished Service Professor in Psychology at the University, and the lead researcher in a team at the University's Institute for Mind and Biology. Chemosignals are substances that while not necessarily perceived as odors, nonetheless have an impact on mood and menstrual cycles when absorbed through the nose.
The researchers found that after being exposed to the breastfeeding compounds for two months, women with regular partners experienced a 24 percent increase in sexual desire as reported on a standard psychological survey. Women without partners experienced a 17 percent increase in sexual fantasies after exposure for the period.
Further study is needed to determine if the chemosignals the team discovered are pheromones. In order to be pheromones, researchers much show that the substances operate "in the context of normal daily interactions with breastfeeding women and their infants. Ideally, such a study would also demonstrate how these effects would have increased the evolutionary fitness of individuals who used this system of social communication during human evolution," McClintock explained.
Other research suggests that women living in early societies produced children when food resources were plentiful. The chemosignal would have been a way of encouraging other women to reproduce when circumstances were optimal.
In 1998, McClintock and other researchers at the institute produced the first evidence of human pheromones.
We are not biological robots, programmed by chemistry, unlike ants and bees. We're not even slaves to chemistry, with limited choices, like dogs and sheep. But we are affected by chemistry, and unaware of it as it bypasses the normal conscious sense of smell. Knowing that, we can make allowances, and act rationally.
Not that there ever was much rational in Love.