Programmer Smack Talk and Global Warming

I've been amused to watch some of the arguments going on out in the blogsphere as discussion of the hacking of the climate change servers moves off into a discussion of the quality of the code being used by climate researchers to model global warming.

Example:

Commenter One: Much of the code in the academic world tends to be written by grad students that have taken a class in programming and get told to write it.

Commenter Two: This is totally untrue. I never took a class in programming before writing my crappy undocumented code.

There's a certain wry self recognition for me here as well: I've never taken a class in programming, and I build mostly undocumented models to predict revenue and profits at specific price points based on past data. My results are directionally correct when you look at whole categories of products, but can be wildly off when projecting specific instances. (I try to make this clear to those who use my data, but people are always looking for certainty in life, even if they have to imagine it.)

The difference is, of course, that I'm seeking to mitigate the risks people take in making decisions that they're going to make anyway. "Gee, I really feel like we need to turn this product 50% off for the holidays." "Well, past experience shows that we wouldn't sell many more units, but would lose a whole lot of money. Let's try something else."

You would think that if you were going to, say, recommend that the entire world ratchet levels of CO2 emmissions back to the levels of the 1800s (with all the impacts to living standards and, let's be honest here, human life, which that entails), you would aspire to higher levels of accuracy and transparancy.

In a sense, I would imagine that these climate researchers have much the same justification for their actions that I do: They're just giving people common sense advise. I advise people not to waste too much profit margin. They advise people not to emit too much CO2.

Waste enough profit margin and your company goes out of business. Get enough CO2 in your atmostphere, and you get to enjoy the kind of climate that Venus has. From the point of view of serious environmentalists, who often seem to assume that any change made by humans to the planet is pretty clearly a bad thing, it may not seem like one needs to bring a lot of rigor to advising people to not burn fossil fuels. From that point of view, of course doing all these "unnatural things" will have bad consequences.

However, for the rest of us, the fact that modern industrial technology allows six billion people to live on this planet -- and for many of them to do so in greater material comfort than at any previous time in history -- is pretty clearly a good thing. And standing in front of that yelling "Stop" requires some pretty rigorous evidence. This isn't something that can be left to buggy code whose results are massaged into shape manually when they're going to come out into the light.

Ardi: Looking at the Latest Missing Link

Virtually everyone with any access to news last week probably heard about Ardi, a 4.4 million year old skeleton of a human ancestor found in Ethiopia. However, given the tendency of the mainstream media to cover every ancient primate discovery as "Scientists discover 'missing link' which 'changes everything'" those who don't track these things can easily become confused, or even rather suspicious of the whole thing.

So, what is Ardi, and why is this discovery a big deal?

Ardi is a 45% complete skeleton of a female individual from the hominin species Ardipithecus ramidus. This is not a new species: we've known about Ardipithecus ramidus since a small number of bones from a member of the species was found in 1992 and formally described and named in 1994. Living about 4.4 million years ago, Ardipithecus ramidus is also not the oldest human ancestor known or a common ancestor between humans and our apparent closest genetic living relatives, the chimps. However, the excitement about Ardi (found along with less complete remains of a number of other Ardipithecus ramidus individuals and also fossil evidence about the plants and animals present in their environment) is not just hype. It is a very important find. Here's why:

Very Complete, Very Old
Invariably, Ardi has been compared to the other famous hominid find, Lucy who made headlines back in the 70s. However, Ardi is both more complete than Lucy and also over a million years older. Lucy was a 40% complete skeleton, about 3.2 million years old, belonging to the species Australopithecus afarensis.

We have a few fossil finds from hominid species which are older than Ardi, but we don't know nearly as much about these species because the finds are much more fragmentary. Sahelanthropus tschadensis lived 6-7 million years ago, but the only fossils found so far of it are a partial skull. Orrorin tugenensis lived 6 million years ago, but all we have is a leg bone and a few fragments. So while basically all we know about these earlier species is that we have a few scraps of bone from a creature that looks to be a hominid and doesn't belong to any other known species, we now have a very clear idea of what Ardipithecus ramidus looked like, and thus what hominids living 4.4 million years ago were like.

A Missing Link
Is Ardi a "missing link"? Well, she (and the other remains found in the same place -- much more partial remains of 35 other individuals) is certainly a missing link in the sense that these fossils provide us with a lot of fascinating information about a certain stage in hominid evolution. But there is no single "missing link" in the hominid ancestry chain. Fossils of primates in general are so rare that piecing together the more distant periods of human ancestry is very, very hard. While the charts we see in books and articles suggest seamless lines of descent, the actual evidence we have is often quite fragmentary, and even the links of the chain that we do have are often only partial. One stage or even a whole species may be represented by only a partial skull or most of a leg -- enough to tell it's different from known species, but not enough to have a very complete picture of the species. The below chart (excuse my poor freehand drawing skills) shows the problem, and why there's often dispute among biologists as to where the actual branches are, and whether we're descendants or cousins of some hominid species.

What is often referred to as "the missing link" is the hope of finding a species which appears to be a direct ancestor of both modern chimps and modern humans. Ardipithecus ramidus is not such a link, and indeed, some researchers are suggesting that Ardi points to that common ancestor being more ancient that previously believed.

What Ardi Tells Us
One of the most interesting things about Ardi is what she seems to indicate about human/chimp divergence. It had been widely assumed at one point that the common ancestor between humans and primates probably looked a lot like a chimp. Our DNA shows that we're closely related to chimps, and because we often have difficulty not thinking about evolution in terms of "progress" (especially when we're talking about ourselves) it's natural to think of chimps as the "ancient" form and to talk about "humans evolving from chimps".

Lucy knocked a bit of a hole in this thinking back in the 70s by showing that upright posture went back to Australopithecus afarensis 3+ million years ago, putting to rest the already crumbling idea that hominids prior to Homo erectus had been "knuckle draggers".

Now we have Ardi, who despite having a big toe that would have allowed her to grip things thing her feet, has a pelvis and legs which are clearly adapted to walking upright 4.4 million years ago. Even the leg bones we have from Orrorin tugenensis 6 million years ago appear to suggest a bi-pedal posture (though it's harder to know from such incomplete remains). So with Ardi's well preserved skeleton for confirmation, it's starting to look very much like human ancestors have been bipedal for a very long time. Large brains and other adaptations are later, but it would appear that it may have been the chimps and gorillas who developed adaptations for arboreal life, and in the process shifted to walking on all fours and putting weight on the knuckles of their hands -- rather than these being features that our ancestors shed.

Ardi did have proportionally much longer arms than more modern human ancestors, and her fingers were long for gripping branches. Her feet could still grip better than ours can (though not as well as modern great apes). Her brain was about the same size as that of a chimp, and she stood about four feet tall (the height of my seven-year-old.) But while she probably did not possess any of the traits that we see as uniquely human (language, higher consciousness, reason, complex tool-making, etc.) she looked less "like an ape" than expectations would have been in the past.

For more detailed information, the following are interesting links:

At long last, meet Ardipithecus ramidus

Ardipithecus: We Meet At Last

And if you really want the mother lode, the journal Science (which put out a special issue with all the original research papers on Ardi) has taken the unprecedented step of making all of the papers available on their site if you fill out a free registration. The Science Magazine Ardipithecus site is here.

Blame the Neolithic

A brief article in The Economist relays some evidence a palaeoclimatologist has recently put forward that anthropogenic global warming began 5000-7000 years ago, as a result of slash-and-burn agriculture spreading throughout Europe and Asia. Or to be less exciting, ice core samples show that CO2 and methane levels started rising 5000-7000 years ago, and since it's known that agriculture was spreading widely at that time, Dr. William Ruddiman of UV Charlottesville (among others) argues that early agriculture may be to blame. Although the world population 5000 years ago was obviously much smaller, the efficiency of agriculture was so much lower (Ruddiman estimates per capita land use was 10x higher than in recent recorded history.

The idea of early societies causing heavy environmental tolls is not new. There's fairly wide support for the idea that deforestation and over-mining contributed to the collapse of the Bronze Age cultures in the Mediterranian. However, the idea that "global warming" started with the late neolithic is kind of charming. Please consider adopting a more hunter-gatherer lifestyle!

More practically, this strikes me as underlining that there is not some single, sacred, stability point which industrial civilization has destroyed. We humans and our planet have always had an effect on each other, and it's virtually impossible for us to avoid that. The course of wisdom lies in trying to avoid making more impact than necessary (while not setting unrealistic goals or stiffling development) and being prepared to deal with unwanted effects that may occur.

Ida and the Missing Link

If you follow science headlines at all, you have doubtless heard about Ida, the diminutive 40 million year old primate who was unveiled to the world this week with nearly unprecedented publicity. Google even got into the excitement with an Ida-themed Google header.

So, what's so special about this find? Is it the "missing link" in human evolutionary history as many mainstream news headlines have suggested?

Well, to the extent that "the missing link" is coloqually used to refer to the most recent common ancestor of humans and chimps, not even close. Ida is more than four times older. Any most paleontologists still aren't sure that the species she belongs to is in our line of ancestry at all. This graphic from the New Scientist shows visually what's being argued about here. What is very much news here is that Ida may help answer some questions about the very, very early history of primates, when the ancestors of modern apes, monkeys and humans were diverging from those of modern lorises and lemurs. However, that's not as exciting a story, so the media seems to be blunding about in the fashion they often do in reporting any specialized field.

The other thing that's incredibly exciting about Ida is that she is an unusually well-preserved fossil, which among early primates is especially rare. (Given that good fossilization requires being quickly covered in fine sediment somewhere like a gentle river, you can see why tree dwelling creatures wouldn't get the treatment very often.) Ida was covered, immediately after her untimely demise, by solf volcanic ash which left a fossil which is 95% complete, fully articulated, and includes prints of her fur and organs.

The precise composition of the volcanic deposits in which Ida was found even allowed preservation of her soft tissue. “You can see the fur, the ears, all of the gut contents [leaves and a fruit], all the fingertips and toes,” Smith says.

Smith and her colleagues were able to guess Ida’s age based on the fossil’s teeth. “She was just turning over and replacing her baby teeth in the front of her face, and the molars were coming in the back,” Smith says. Because Ida had many teeth forming at the same time, Smith thinks the primate must have grown up fast, developing much quicker than a human would. Ida died before she was 1 year old, Smith and her colleagues suggest. Comparisons with a similar animal, the squirrel monkey, led the researchers to guess that Ida might have lived for 15 or 20 years had she not met an early demise.

This has allowed us to get an unusually accurate view of what this early primate looked like. She's rather fetching, really.

The full paper on her (from which that sketch comes) can be found here.

Children of the Corn

Here to the north of Austin, we live in an odd patchwork of new neighborhood, business parks and shopping malls interspersed with open fields. Cattle graze in the field next to our supermarket, and corn grows cross the street from our bank.

Seeing the orderly fields of corn, I'd never realized that corn represents an intriguing mystery in regards to plant evolution and the history of humanity's interaction with the plants we live off of. First domesticated in Central America around 7000 years ago, corn as we find it today is a domestic-only plant in that it is virtually incapable of reproducing in the wild.

One of the characteristics of corn that makes it such a useful crop is the incredibly high return of kernels harvested to kernels planted. Biologically, one of the reasons for this abundance is that unlike other grasses which have been domesticated as agricultural grains, the corn cob forms halfway down on the plan, closer to sources of water and nutrients, and thus the plant is able to put more energy into seed growth. In other cereals, the seeds are at the very top of the stalk, at the plant's farthest extremety.

Another great feature of corn is that the cob is covered by a husk, which largely protects the grain from pests. It pretty much requires a creature with opposable thumbs to get the husk off, which means you loose less of the grain prior to harvest. Plus, the kernels are well-rooted into the cob, as compared to grains like wheat where the ripe seeds can easily fall from the ear of grain.

However, all of this -- particularly the firmness of the kernels in the cob and the husk covering it -- means that if there are no humans to harvest the corn, very, very little of it will succeed in naturally reseeding. If a cornfield were abandoned before harvest and you returned in five years to see if any wild corn was left growing, you would probably find few to no corn plants.

This means that corn as we find it today must be biologically fairly different from the corn ancestor which Central Americans first found in the wild and domesticated. The predominant theory out there is that corn is descended from the grass called teosinte which is found in Mexico even today, but the differences between the two plants are extensive, though there is enough genetic similarity to make it pretty clear they are related. Teosinte grains is far out on the extremities of a banching stalk, the grains are covered by hard outer covering (like the chaff of wheat), the grains are not strongly rooted in a cob-like structure, and they are not covered by a husk that remains closed.

The National Science Foundation has a nice comparison here:


The prevailing theory at the moment is apparently that teosinte underwent a series of major mutations during a very short period of time which resulted in the corn we see today. I find that a bit unsatisfying, since series of major, conventient, stable mutations are hard to come by. Thus I was interested to find this article about Prof. Mary Eubanks of Duke University, who has been working on the theory that corn as we know it today is the result of multiple hybridizations between teosinte and another wild grass called tripsacum. She's developed a hybrid of tripsacum and modern corn which exhibits many of the properties of the ancient ears of corn dating back 5000+ years that have been found in caves in Mexico. Apparently she has pretty decent genetic evidence for this as well by now.

While I'm not remotely an expert, I must admit to finding the hybridization explanation somewhat more convincing on the face of it than the sudden large mutation explanation. And I had never realized that corn was so interesting.

Philosophy and Health

Philosophy is often seen as one of those highly impractical, strictly academic fields, and yet, it has a way of being at the root of everything.

I was struck, recently, by a contrast in two statements about medicine. In an article about the importance of finding medical ways to enhance female sex drive, I ran across a claim along the lines of, "Many experts believe that more than 50% of women over 30 suffer abnormally low interest in sex and would benefit from sexual drive enhancing medication if it became available." The immediate connection my mind made was: No more than 5% of the population is attracted primarily to his or her own sex, and yet this is not considered a medical abnormality.

These two together show that the medical community (and our society in general) clearly has some sort of philosophy of the human person and philosophy of sexuality, which is doubtless assumed and unstated. Women, it is believed, ought to have a sexual drive equal to that of men, regardless of whether that is what we find in nature or not. (Even though there are some obvious evolutionary reasons why males would be physically more interested in frequency of copulation than females.) And yet if one primarily experiences sexual attraction to one's own sex, even though that both "doesn't fit the plumbing" and is evolutionarily useless, that is perfectly fine and healthy, even if this is a condition found in only a small percentage of the population.

Medicine is, in its modern form, generally an empirical field. Yet the question of "What is normal?" and "What is abnormal?" is a question that we always answer philosophically rather than empirically.

Necessarily so. Often our sense of what "ought" to happen is directly contrary to the observed usual occurrence. "Health" is not simply what we observe to be the usual, otherwise we would consider the "healthy" result of a diagnosis of lymphoma to be death.

We chase the telos just as much as in Aristotle's time, and yet we do not acknowledge that what we are doing is anything other than an "empirical science".

Empirical Methodology vs. Human Nature

Sorry to be naught but a linker this week, but things have been busy...

This New York Times Magazine article, interviewing three female researchers studying female desire, struck me as an interesting example of how scientific methodologies are of limited use in describing the human person. Many of their conclusions and ideas are interesting, and you can see how they reflect lived experience to a limited extent, but the fruits of all this research are also startlingly inadequate in describing something as universally experienced as human love and sexuality. And necessarily so, I would tend to think.

Contraceptive or Abortive?

Clearly as Catholics, we're not supposed to be doing either one, nor do I have any desire to, but in regards to questions of conscience and regulation the facts of the matter are clearly important. It's been discussed often in pro-life circles over the years that oral contraception is designed such that it sometimes allows fertilization but prevents implanation -- thus in effect causing a spontaneous abortion several hours after conception. This is generally applied even more so to "morning after" pills, which is a reason why some pharmicists have conscience objections to dispensing such medications. Given that that Protestant half of the pro-life movement is often fairly comfortable with birth control in concept, this "the pill causes abortion a certain percentage of the time" argument has often been used to help unify the pro-life movement against birth control.

Regardless of whether it's true, I think that clearly the contraceptive mentality and the approach to sex it entails is certainly a major cause of support for abortion.

All that said, I'd very curious as to the reaction of Catholics more educated in the precise medical details of human reproduction than I am to this Slate post, which argues that the evidence for abortificant properties to The Pill and Plan B is slim to none.

I've no particular interest in endorsing Saletan's opinions generally, he's the one who made the to my mind rather nutty argument a while back that Planned Parenthood was overall an anti-abortion organization because contraception prevents unwanted pregnancies. But if it's correct as a matter of medical science that it's very, very rare for oral contraceptive and even "morning after" pills to cause spontaneous abortions, we'll do nothing but make ourselves look unconcerned with the truth (and the scientific truth of embryology is very much on our side when it comes to what the pro-life movement says about abortion as opposed to what the "just a clump of cells" people say) if we keep pushing it.

Feedback from those with medical or scientific knowledge of the issue would be appreciated.

Raising The Dead

If, as I did, you spent much of your youth reading about creatures of the past, and especially if you had a chance to frequent museums, as I did the Page Museum at Los Angeles' La Brea Tar Pits, the idea of seeing some of the large land mammals which went extinct within the last 50,000 years brought back to life can't help seeming a bit attractive.

Who could resist the chance to see an American Mastodon (above) or a Smilodon, or "saber-toothed cat" (below) alive again?


Scientists are increasingly thinking that it would in fact be possible to produce live specimens of recently extinct mammals, such as the Woolly Mammoth, which died out in Europe and America (like the above creatures) only around 8,000 B.C.


The cause of these extinctions was probably dual: changing climate after the end of the last glacial period, and excessive hunting by humans. That virtually all large mammal species (among them the American Horse and American Camel) other than the American Bison vanished from North America shortly after the flourishing of human populations here is probably not entirely a coincidence. (A similar pattern occurred in other parts of the world, notably Australia where a number of large marsupial species died out right after the arrival of humans.)

Given how recent these extinctions were, there's fairly "fresh" genetic material still around from them, and fairly close living relatives around to serve as surrogate parents, so of course as genetic technology advances scientists have become increasingly interested in trying to bring back one or more of these recently extinct species by means of using original genetic and cloning type procedures. The New York Times reports:

Scientists are talking for the first time about the old idea of resurrecting extinct species as if this staple of science fiction is a realistic possibility, saying that a living mammoth could perhaps be regenerated for as little as $10 million....

A scientific team headed by Stephan C. Schuster and Webb Miller at Pennsylvania State University reports in Thursday’s issue of Nature that it has recovered a large fraction of the mammoth genome from clumps of mammoth hair. Mammoths, ice-age relatives of the elephant, were hunted by the modern humans who first learned to inhabit Siberia some 22,000 years ago. The mammoths fell extinct in both their Siberian and North American homelands toward the end of the last ice age, some 10,000 years ago.

Dr. Schuster and Dr. Miller said there was no technical obstacle to decoding the full mammoth genome, which they believe could be achieved for a further $2 million. They have already been able to calculate that the mammoth’s genes differ at some 400,000 sites on its genome from that of the African elephant.

There is no present way to synthesize a genome-size chunk of mammoth DNA, let alone to develop it into a whole animal. But Dr. Schuster said a shortcut would be to modify the genome of an elephant’s cell at the 400,000 or more sites necessary to make it resemble a mammoth’s genome. The cell could be converted into an embryo and brought to term by an elephant, a project he estimated would cost some $10 million. “This is something that could work, though it will be tedious and expensive,” he said.

I must admit, I find this a rather exciting idea. However, it seems that no sooner do people come up with the ability to do something like this than they get other ideas:

The same would be technically possible with Neanderthals, whose full genome is expected to be recovered shortly, but there would be several ethical issues in modifying modern human DNA to that of another human species.

Love the charming understatement of "there would be several ethical issues in modifying modern human DNA to that of another human species", eh?

Oh, but fear not. We've got some deep thinkers here who are working hard to make sure that they don't engage in any research that treads ethically thin ice:

But the process of genetically engineering a human genome into the Neanderthal version would probably raise many objections, as would several other aspects of such a project. “Catholic teaching opposes all human cloning, and all production of human beings in the laboratory, so I do not see how any of this could be ethically acceptable in humans,” said Richard Doerflinger, an official with the United States Conference of Catholic Bishops.

Dr. Church said there might be an alternative approach that would “alarm a minimal number of people.” The workaround would be to modify not a human genome but that of the chimpanzee, which is some 98 percent similar to that of people. The chimp’s genome would be progressively modified until close enough to that of Neanderthals, and the embryo brought to term in a chimpanzee.

“The big issue would be whether enough people felt that a chimp-Neanderthal hybrid would be acceptable, and that would be broadly discussed before anyone started to work on it,” Dr. Church said.

I'm sorry, perhaps I shouldn't be flip and derisive, but in the words of my generation: Is this guy for real?

Does he really imagine that the big moral objection that people have to the idea of cloning Neanderthals is just a matter of whether a human egg or chimp egg is used?

The Neanderthals were around until about 25,000 years ago. They made complex tools, wore simple jewelry, made clothes, buried their dead, used fire, and there's fairly strong evidence that they also created art and had equal speech abilities to modern humans. One of the main controversies about Neanderthals is whether they are a separate species in genus homo or a separate sub species within homo sapiens (homo sapiens sapiens vs. homo sapiens neandertalis).

Even leaving aside thorny religious questions (of which I think there are definitely many -- given that I don't think creating genetic knock-offs of modern humans is remotely acceptable, and also given that the evidence is decent that the Neanderthals were themselves religiously aware in some sense, and thus not to be taken as a non-entity in the question) this seems like an appalling idea from a strictly humanitarian perspective. Create one or more "resurrected" members of an extinct group of humans as a scientific and technical stunt? A group of humans which clearly had mental and physical (and I would assume thus emotional) characteristics not so different from our own -- and yet almost certainly different as well.

Would the researchers "own" these Neanderthals? Would they be citizens with their own rights? What kind of life are you setting someone up for by artificially bringing him into the world 25,000 years after those like him died out, and making him a curiosity among a sea of those similar yet not the same?

Don't get me wrong, I can certainly find the idea of meeting other types of humans interesting, but artificially creating them strikes me as not only irresponsible, but inhumane.

Well, I'm apparently not the only one who had some ethical questions about the article, because the New York Times chose to run an editorial about the article. Their ethical concern?

The first mammoth would be a lonely zoo freak, vulnerable to diseases unknown to its ancestors. To live a full and rewarding life, it would need other mammoths to hang out with, a mate to produce a family and a suitable place to live. The sort of environment it is used to — the frigid wastes of Siberia and North America — are disappearing all too fast...

If scientists do bring back a few mammoths, we suspect our warming world won’t look any more hospitable than the one that did them in.

Yes, they ponder whether it would be moral to bring a woolly mammoth into a world with global warming.

Do you ever get the impression there are people with very different philosophical and moral compasses than your own in our country?

The Pill and Mate Selection

This has been bouncing around the Catholic blogsphere due to being picked up by the blog at First Things, but I post it here in hopes of perhaps drawing a comment out of Razib or someone else with some more serious biological knowledge. It would seem that evolutionary psychologist Stewart Craig Roberts has a paper coming out in the current issue of the Proceedings of the Royal Society: Biological Sciences in which he presents data that women show different odor-based preferences in regards to men when they are pregnant and when they are on The Pill (which uses hormones to reproduce some effects of pregnancy, thus surpressing ovulation.)

While several factors can send a woman swooning, including big brains and brawn, body odor can be critical in the final decision, the researchers say. That's because beneath a woman's flowery fragrance or a guy's musk the body sends out aromatic molecules that indicate genetic compatibility.

Major histocompatibility complex (MHC) genes are involved in immune response and other functions, and the best mates are those that have different MHC smells than you. The new study reveals, however, that when women are on the pill they prefer guys with matching MHC odors.

MHC genes churn out substances that tell the body whether a cell is a native or an invader. When individuals with different MHC genes mate, their offspring's immune systems can recognize a broader range of foreign cells, making them more fit.

Past studies have suggested couples with dissimilar MHC genes are more satisfied and more likely to be faithful to a mate. And the opposite is also true with matchng-MHC couples showing less satisfaction and more wandering eyes.

"Not only could MHC-similarity in couples lead to fertility problems," said lead researcher Stewart Craig Roberts, an evolutionary psychologist at the University of Newcastle in England, "but it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill, as odor perception plays a significant role in maintaining attraction to partners."

The study involved about 100 women, aged 18 to 35, who chose which of six male body-odor samples they preferred. They were tested at the start of the study when none of the participants were taking contraceptive pills and three months later after 40 of the women had started taking the pill more than two months prior.

For the non-pill users, results didn't show a significant preference for similar or dissimilar MHC odors. When women started taking birth control, their odor preferences changed. These women were much more likely than non-pill users to prefer MHC-similar odors.

"The results showed that the preferences of women who began using the contraceptive pill shifted towards men with genetically similar odors," Roberts said....

"When women are pregnant there's no selection pressure, evolutionarily speaking, for having a preference for genetically dissimilar odors," Roberts said. "And if there is any pressure at all it would be towards relatives, who would be more genetically similar, because the relatives would help those individuals rear the baby."

So the pill puts a woman's body into a post-mating state, even though she might be still in the game.

”The pill is in effect mirroring a natural shift but at an inappropriate time,” Roberts told LiveScience.

Obviously this is just one factor in relationship dynamics, but it does strike me as interesting in that it seems http://www.blogger.com/img/gl.link.gifto me that birth control is a fairly culturally disruptive technology which generally speaking was taken up without a whole lot of thought about anything other than the obvious benefits.

It's also an example of the ways in which things we don't think of affect our feelings and actions. No one, I'm sure, would think, "Boy, my boyfriend just doesn't smell alluring anymore." (Unless, perhaps, she was about to tell him to go take a shower rather than plopping down on the couch next to her after returning from the gym.) But a thought of, "He just doesn't seem exciting anymore" or "We just don't seem to have a spark these days" might well include a response to senses that we do not actively think about.

UPDATE: Razib puts up a good post on the question here. And provides a link to the original study here.

Worth noting is the confluence of interests that gives this story so much play. In the mainstream press, it's a quirky result about something which nearly everyone takes -- probably good mostly for a laugh. "Hey, did you hear the one about how your girlfriend is more likely to dump you for her brother when she's on the pill?"

Meanwhile, in the small subculture of those who have rejected birth control, it serves as a bit of an "I told you so".

In the end, it strikes me as a bit interesting -- more as an example of how a physical reaction can unconsciously affect our personal choices than as a proof that women on the pill will form bad relationships. (After all, there's nothing that would necessarily make a relationship with someone who happened to have a more similar immunity profile a "bad relationship".) Much more concerning, if one is listing off reasons to be cautious of the wide use of birth control, is that having fertility be strictly optional removes the biological incentive from a lot of ancient social structures that we pretty much take for granted, and don't want to see go away.