Call me when they invent a pill that just gets rid of menstruation, and isn't a birth control pill. I sometimes think our whole discussion women's monthly cycles is focused way too much on menstruation, only discussing ovulation as it pertains to pregnancy risk. Benefits of monthly ovulation:
1. Mood is almost always better during ovulation than during menstruation (I can provide the research citations on this). Lybrel eliminates the downside of menstruation, but doesn't give you the upside.
2. Researchers have shown that sense of smell is key to humans' finding a mate. Sense of smell helps people find mates they are biochemically compatible with (has to do with immune system matching). However, this sense of smell is only accurate when women are ovulating. Turn off ovulation, and you lose a certain amount of "chemistry." Many women on the pill who get married and then go off the pill discover that they no longer find their mates sexually appealing. Women are also more likely to seek out physically attractive mates when they are ovulating. So there's a cost to interfering with the sensitivity of one's own "mate-choice" devices. (See research by Wedekind in Proceedings of the Royal Society, B, and by Doug Kenrick).
3. Women have a higher sex drive when they're ovulating and for a few days around it than at any other point in the cycle. Personally, I'd hate to interfere with that.

All I'm saying is that there are other reliable ways to prevent pregnancy. Vasectomies are reversible - let men mess with their bodies. I like my ovulation, and have happily never been pregnany. No Lybrel for me!

AND ALSO,

Men find ovulating women more attractive and women report orgasming more easily when ovulating. As a male, that's why I like ovulation. BUT, an ovulating woman is more likely to cheat on her long term partner. (I too can site some journal articles, if need be).

I would like to see a reference from a peer reviewed scientific journal that shows a link between scent and the immune system.

The bulk of the research revolves around the MHC (Major histocompatibility complex). Basically, the theory is that humans can use olfactory cues to determine how much their potential mate's MHC gene sequence varies from their own. Since MHC holds many of the genes responsible for immune response, selecting a mate with a differing sequence will convey greater variation in your offspring's immune response (increased heterozygosity). One of the first papers detailing the research is here:

Wedekind, C., & Füri, S. (1997). "Body odor preference in men and women: Do they aim for specific MHC combinations or simply heterozygosity?" Proceedings of the Royal Society of London B, 264, 1471–1479.

Using ISI or some other cite linking site you should be able to find more recent research linking to this paper.

Oh and also, this paper sort of summarizes at lot of the research:

Thornhill, R., & Gangestad, S.W. (2003) "Evolutionary Theory Led to Evidence for a Male Sex Pheromone That Signals Symmetry" Psychological Inquiry, Vol. 14, No. 3&4, 318–325

And this paper specifically looks at the role of oral contraceptives on a males ability to tell if a female is ovulating, concluding: "Furthermore, the contrasting results
between pill users and nonusers may indicate that oral contraceptives demolish the cyclic attractiveness of odors."

Kuukasja¨rvi, S. et al. (2004) "Attractiveness of women’s body odors over the menstrual cycle: the role of oral contraceptives and receiver sex." Behav Ecol 15:579–584

Do you have access to a database?

Thanks for doing the legwork on this. I was able to pull up the Wedekind et al body odor/MHC paper but couldn’t get the paper published in Psychological Inquiry (besides I asked for a scientific journal and a psychology rag doesn’t meet that criteria, ha). The third paper deals with body odor and menstruation, I’m interested in the claim concerning the immune system. In general there is much more literature on this subject than I had assumed. Although, as the authors describe this theory is still lacking a physiological mechanism. My original criticism was due to prime8’s statement, “Researchers have shown that sense of smell is key to humans' finding a mate.” Whether or not this theory is true, calling it a key to finding a mate goes beyond what was tested. Pheromones may have a role in mate selection but we don’t know where that ranks among the other mate selection traits like religious affiliation, health, economic potential and attractiveness. I also have difficulty with the looseness of the term mate. Jared Diamond makes the point in “The Third Chimpanzee” that when we look for a mate but aren’t yet interested in offspring our choice is very different then when we are looking for someone to start a family. Briefly, the first group enjoys experimentation and the adage opposites attract apply. When looking for a mate to sir offspring we are much more concerning and we often chose the familiar; we marry our moms or dads. The analysis performed with the subjects that had a memory associations of past mates were most likely (the smellers aren’t described but are probably college students) of the former group, were not seriously planning offspring with the “mate”. Diamond’s theory of opposites attracting for non-offspring mating is also consistent with the data (greater MCH difference than would be expected if random) without an MHC/pheromone mechanism. My last point is only half of the t-shirt wearers could on average have their gender guessed. This result shows to me that the experimental design isn’t sophisticated enough to address this question. Are we to believe it is possible to determine a person’s MHC allele make-up with a smell but can’t determine their gender? I think more caveats are needed when describing this field then was used in this thread.

In general I agree with everything you said: I think more research is needed and I don't think "key" was the right-word (didn't know you were honing in on that though).

But, I would say that it very well may be possible to determine MHC without knowing gender. If the odor expressing the MHC breakdown is not gender-specific (studies show both men and women use it) why would you expect otherwise?

Secondly, you're observation that we can look for a mate without look for a parent of our offspring isn't perfect. Until very very recently sex=babies. There is a difference in strategies between long-term mates from which he help to get support, and short-term mates from which we only hope to get good genes. It's where these two strategies cross that the really cool stuff in evolutionary psychology takes place. But make no mistake, both long-term and short-term strategies are about making good babies.

Why presume monagmy is the be all end all of a relationship in the first place? Its like defacto slavery. Ovulation and orgasms aside.

monogamy is supposed to be the end all be all of a relationship due to evolutionary demands. most life evolves into its adulthood fairly rapidly, no more than 1-2 years at the extreme. some are ready to be on their own in days or weeks. humans however need several years to be able to survive on their own (call it 8-10 at a minimum, we don't even start maturing into our adult bodies until age 12 or so). its because of this that humans evolved to stay together after conception/birth, the child needs a stable environment to learn the necessary skills to survive.

I disagree. In the breeding process by having multiple partners you increase genetic diversity furthermore, polycultural systems are just as successful in offspring maturity. for every example for monogamy there are equally valid examples for polygomy. The argument that on or the pther provides a better stable environment for the child is subjective. Had you been raised in a comparable poly community culture you would be raised "stable".

>> But, I would say that it very well may be possible to determine MHC without knowing gender. If the odor expressing the MHC breakdown is not gender-specific (studies show both men and women use it) why would you expect otherwise? <<

I remain highly dubious to the entire idea that there is a connection between MHC and odor. The experiment using dirty t-shirts and smellers is hardly conclusive. In contrast I find the idea that a man can detect an ovulating women to be plausible, and in the same vein, able to determine gender. Just a guess.

>> Secondly, you're observation that we can look for a mate without look for a parent of our offspring isn't perfect. Until very very recently sex=babies. There is a difference in strategies between long-term mates from which he help to get support, and short-term mates from which we only hope to get good genes. It's where these two strategies cross that the really cool stuff in evolutionary psychology takes place. But make no mistake, both long-term and short-term strategies are about making good babies.<<

Evolutionary psychology? I hope we don’t have to wade into that infantile battlefield to explore this topic. I agree that my “mating without a desire to sire” is much better expressed as strategy of providing genes without any long-term help. I also agree that the expectation of getting long-term help is a very important criteria when choosing a mate, and as others have expressed, what the traditional relation between the sexes is important in that discussion. The research I have seen focused on the size difference between men and women, and the size of male’s testicles. Compared to animals where the male has many females in a harem-like relationship (like elephant seals) the size difference between human males and females is slight. Yet, human males are slight bigger then females, which isn’t typical of a species that is strictly monogamous (Gibbons). Likewise, the large size of the human testicles (relative to other primates) suggests there is a competitive advantage for large amounts of sperm. Large male elephant seals fight to win the females but after that the competition is over and large testicles aren’t necessary. For animals in which females willingly have multiple sex partners, large male size isn’t as important as large testicles; the competition takes place in a much more pleasant venue. Taken together, the data suggests that in our past humans had some experience with harems and that extramarital affairs aren’t uncommon. As ugly as it may seem, a successful strategy may include females first trying to pick a mate that will be a committed partner and then trying to sneak a chance at a “better” gene pool with a different mate; while keeping the committed partner in the dark. Likewise, males join committed relationships and then try to increase their progeny by getting others to do the hard work. Therefore, a key determinant when choosing a mate may depend on if you already have a committed partner. If not, finding someone honest (when they promise to help) may be more important than attractiveness or a diverse MHC profile. But once the first the need is fulfilled, the temptation to try for a mate whose offspring will be capable of providing more meat (in the case of the female) or the temptation of spreading as much seed as possible (in the case of the male) is evolutionarily hard to resist.