Indifferential Diagnosis #1: Visual Hallucinations

Welcome to a new feature in which we explore the various fascinating conditions that can cause various fascinating symptoms, kicking off today with visual hallucinations. Since the goal is curiosity, rather the actual medical utility, these won’t be exhaustive lists of causes. I will include only those conditions that I deem worthy of my time and yours. Additionally, I can’t promise that this feature will be delivered with monthly regularity. I was imagining a timeframe more along the lines of “whenever I feel like it”. That said, I would like to offer the last and most important disclaimer: I am not a doctor and indifferential is not a word. The rest of the information contained here is true to the best of my knowledge. Feel free to use it at dinner parties and when competing against computers on game shows.

A visual hallucination can be summarized as the perception of  an external image in the absence of any existing object. This is different from an illusion, in which one perceives a distorted view of one’s surroundings. Visual hallucinations can be simple (shapes and colors) or complex (vivid landscape or figures). Both categories vary not only in their causes, but also in their appearance, a variation that can at times provide insight into the source of the problem.

Schizophrenia

While many associate visual hallucinations with mental illness, this symptom is not particularly common in schizophrenia or other psychotic disorders. The bulk of hallucinations occurring in schizophrenia are auditory. When visual hallucinations do occur, they are generally complex and may involve humans, animals, and religious figures. The specific content of these visuals may have symbolic value to the person seeing them and are often threatening, or even hostile toward the viewer.

Tell-tale signs: Schizophrenia usually manifests with a host of other psychological symptoms – auditory hallucinations (often disparaging in content), delusions, and disorganized thought – that easily separate it from most of the other conditions we will be looking at.

Migraines

As you probably know, a migraine is a really, really, really bad headache. They can last hours to days and may be accompanied by light sensitivity, nausea and vomiting. If this weren’t bad enough, about a third of migraines commence with a phenomenon known as an “aura” that includes a hallmark visual hallucination. This starts with a simple, usually colorless, flickering and then proceeds to a zig-zag line that spreads from the center of the visual field outward, often leaving a vision-obscuring blotch (called a scotoma) in its wake. The good news is that this phase will be over in an hour or less. The bad news is that if will be followed by an excruciating headache.

Tell-tale signs: The horrible pain associated with a migraine is a pretty good give away as to the cause of this hallucination. Unless, of course, you suffer from…

…Occipital Lobe Seizures

The occipital lobe is the part of the brain where visual processing occurs, so it’s not surprising the electrical abnormalities in this region can cause visual hallucinations. Unlike the classic tonic-clonic (“grand mal”) seizure, which affects the entire brain and features loss of consciousness and convulsions, occipital lobe seizures are pretty subtle.* An observer of such an event may see nothing more than rapid fluttering of the eyelids. But to the person having the seizure, things look quite different. As with migraines, visual hallucinations attributed to this condition are simple and have a consistent design. They are brightly colored and dominated by many circular or spherical shapes. However, the lightshow is much shorter than that of the migraine aura, lasting no more than a few minutes. Despite striking differences in visual content and duration, occipital seizures are frequently mistaken for migraine auras. This is because up to half of such seizures are followed by headaches.

Tell-tale signs: If you’re lucky enough to have health insurance, epilepsy can often be confirmed with an expensive EEG. Just be sure to bring a hat, because they stick those recording electrodes right in your hair with some nasty gel that won’t come out until it’s shampooed.

Charles Bonnet Syndrome

And now we return to the realm of complex visual hallucinations. Charles Bonnet syndrome (CBS) is a condition in which subjects with impaired vision start seeing things. The hallucinations are vivid and elaborate and can involve figures and animals.† They tend to begin in the evening and can last for hours. CBS is most common in older people (possibly because their rate of failing eyesight is higher than the general population) and is unfortunately sometimes mistaken for age-related mental deterioration. However, unlike the complex hallucinations experienced by psychotic patients, these are strikingly lacking in symbolism and contain no special meaning to the people experiencing them.

Tell-tale signs: Oldness and/or near-blindness. Additionally, patients with this condition are perfectly aware that what they are seeing is not real and, aside from nagging doubts about the state of their sanity, generally do not find the hallucinations especially bothersome.

Sleep Disturbances

Didn’t I already cover this back in October? It’s true though, visual hallucinations can occur during transitions between waking and sleeping states of consciousness.

Tell-tale signs: It’s dark and/or you’re in bed.

Alcohol Withdrawal

With all due respect to the alleged horrors of opiate withdrawal, I must say that delirium tremens (aka the DTs) sounds utterly miserable. It occurs following the abrupt cessation of ethanol consumption after a long period of heavy drinking. Symptoms begin with the characteristic tremor and progress to include fever, confusion, agitation and, of course, visual hallucinations. In addition to being unpleasant, this particularly ugly variation of chemical withdrawal can be fatal. The hallucinations vary in duration (brief to almost continuous) and often involve animals. And these aren’t always cute cuddly animals, visions of snakes and insects have been reported by some patients. The severity of delirium tremens can be reduced with benzodiazepines (Klonopin and company), which ironically can also be habit-forming and feature similar withdrawal symptoms if discontinued too suddenly.

Tell-tale signs: Um, history of heavy drinking, shaking, etc. Really, this one sounds kind of hard to miss.

* Seizures that begin localized in one portion of the brain can spread to the rest of the organ, so those prone to occipital lobe seizures may also suffer from grand mal seizures.

† One patient reported seeing Highland cattle grazing in his living room.

Who told you this?

Teeple, R.C. et al. 2009. “Visual Hallucination: Differential Diagnosis and Treatment.” Prim Care Companion J Clin Psychiatry 11: 26-32.

Manford, M. and Andermann, F. 1998. “Complex visual hallucinations, Clinical and neurobiological insights.” Brain 121: 1819-1840.

Panayiotopoulos, C. P. 1994. “Elementary visual hallucinations in migraine and epilepsy.” J Neurol Neurosurg Psychiatry 57: 1371-1374.

Jacob, A. et al. 2004. “Charles Bonnet syndrome – elderly people and visual hallucinations.” British Journal of Medicine 328: 1552-1554.

Doctor’s Orders

Last month marked the 38^th anniversary of the United States Supreme Court decision in the case of Roe v. Wade, which established abortion as a woman’s fundamental right under the U.S. constitution. President Obama spoke on his support of the decision, asking Americans to, “recommit ourselves more broadly to ensuring that our daughters have the same rights, the same freedoms, and the same opportunities as our sons to fulfill their dreams.” Normally, I couldn’t have cared less about relaying such information here. As its name asserts, this blog deals with science. I try to avoid politics. It’s messy and uncouth. But sometimes politics worms its way into science and I am thus coaxed into acknowledging it.

Due to recent shifts in the political balance of power in this country, the abortion debate has been more front and center than usual. It has figured prominently in challenges to the health care act and is a popular topic in conservative rhetoric preparing for the next presidential election. But, as I said, I try to stick to science here. So I’m not going to write about how, in a country where 35% of women live in counties without a single abortion provider, state laws requiring in-person counseling followed by a 24-hour waiting period create an undue burden for lower-income women. Nor will I explain how excluding abortion coverage from federally funded health programs similarly punishes the poorest women, for whom the average $450 cost of a non-hospital abortion can be prohibitively high. These are matters of politics.

Instead, I will focus exclusively on the science behind certain states’ abortion policies. While federal law overrides any state laws banning abortion, states have the power to create some restrictions to abortion access. Often these take the form of waiting periods and parental consent for minors, but several states also have laws mandating that health care providers “inform” women seeking abortions of one or both of the following; A) that abortion increases their risk of developing breast cancer and B) that abortion can cause depression and other mental health problems. These are frightening things to be told and one would hope that lawmakers would not create these policies without good reason. But is there any evidence behind such claims? Well, it sort of depends on what you’re willing to accept as evidence.

DATA GATHERING*

The trouble with many of the studies on both of these alleged links is that they are correlation studies. Randomized controlled trials are the approach used in much of medical testing (efficacy of new drugs for instance), but it is considered unethical to randomly assign abortion/non-abortion outcomes to pregnancies in human subjects. The only way to examine something in which subjects rather than researchers makes such choices is by looking for correlations between two variables. For instance, are individuals diagnosed with lung cancer more likely to be life-long, heavy smokers than those without the disease? † Easy enough. However, you can’t actually infer causality from correlation. Such inferences can miss a third variable that is responsible for the other two. A favorite teaching example of this error is the conclusion that ice cream consumption causes drowning, because rates of both rise and fall in the same pattern. Of course, it is a third variable – hot weather – that increases both swimming (and therefore chance of drowning) and the interest in frozen desserts. Interpretation of correlation data can also mistake a symptom for a cause - for instance, the assumption that marriage counseling causes divorce. What is useful about correlation studies is that they can uncover relationships (or lack thereof) that suggest causality. But the only way to verify cause and effect is with actual experimentation.

Case-control vs. Cohort

In addition to the pitfalls of interpretation mentioned above, correlation studies also vary in format. In case-control studies, a group of people with a particular diagnosis (case subjects, such as women with breast cancer) are matched with another group without the diagnosis (control subjects, such as women without breast cancer) and both groups are reviewed for a variable that is a suspected link (such as reproductive history). A cohort study instead looks at a large population and records a variety of life-history information, and then examines the correlation between variables of interest. A cohort can be a group of individuals living in a particular country, or working in a particular profession, and so on. Often, multiple studies can be created from data gathered on one cohort. Cohort studies are considered to be more reliable than case-control studies.

Retrospective vs. Prospective

One of the reasons case-control studies can be inferior to cohort studies is that the former is generally retrospective, while the latter can be either retrospective or prospective. A retrospective study begins with the outcome (cancer) and looks backward in time to find the potentially correlating variable (reproductive history). Often this is done through interviews or questionnaires, which can be biased. Conversely, prospective studies start with the variable of interest and then follow a cohort to see if a particular outcome occurs. While they can be lengthy and expensive to conduct, prospective cohort studies are about as reliable as it gets in the world of correlation.

ABORTION AND BREAST CANCER

While sporadic research into a possible connection between breast cancer risk and reproductive factors goes back to the early 20^th century, interest in the effect of abortion really picked up during the 1980’s. Doing a literature search on the subject, one encounters a sea of contradictory conclusions, with some finding increased risk, others finding no correlation and some actually reporting decreased risk. As you may have guessed, much of this frenzied, first wave of research took the form of retrospective case-control studies. More recent prospective cohort studies have greater consistency in their results - usually finding no correlation between abortion and breast cancer.

Research interest in this subject was probably fueled in part by controversy over abortion, but it is not unreasonable to consider whether there might be a connection. There has been some indication that full-term pregnancies early in life confer protection against breast cancer. Conversely, pregnancy later in life (and, it turns out, post-menopausal hormone replacement therapy) can increase cancer risk. Since the hormones associated with pregnancy can have positive and negative repercussions, it is worth examining what effect an incomplete dose of these hormones would have on women’s health. But recall that not all incomplete pregnancies are the result of induced abortions. Spontaneous abortions (aka miscarriages) are another possible outcome of pregnancy. Interestingly, studies looking at spontaneous abortions generally find no correlation with breast cancer.

Why should induced abortion have greater correlation with breast cancer than does miscarriage? Well, now we come back to the problematic biases of the dreaded retrospective study. As you may have noticed, induced abortion carries with it more social stigma than miscarriage. Women who obtained abortions are thus more likely to omit this information than women who suffered miscarriages. Additionally, it has been suggested that the tendency to inaccurately report induced abortion history may differ in women who have and have not been diagnosed with breast cancer. Like many people with life-threatening diseases, women with breast cancer, hoping to provide accurate information that might contribute to disease cure or treatment, are more inclined to admit to having had an abortion. Healthy women lack this motivation for honesty. Thus, in retrospective studies, women with breast cancer may report a greater number of abortions not because their rate is actually higher than healthy women, but due to their greater willingness to disclose the information.

One way of getting around the problem of biased self-reported data is to rely exclusively on medical records. Several interesting cohort studies have been conducted using the handy national registries of Denmark. Unlike the U.S., Denmark provides its citizens with universal health care, and all such medical transactions (cancer diagnosis, mental health care, births, abortions, etc.) are logged into various registries. Information from the registries can be anonymously matched using numbers assigned by the Civil Registration System. A 1997 study published in The New England Journal of Medicine used the Danish registries to follow one and half million women. They found no correlation between induced abortion and breast cancer.

While the volume of correlations studies of this subject continues to increase, there is still a conspicuous absence of a demonstrated mechanism for how induced abortion might impact cancer development. Several pregnancy hormones have been associated with the cancer-protective benefits of pregnancy. One of these is human chorionic gonadotrophin (hCG), ‡ which actually peaks during the first trimester of pregnancy rather than lingering throughout like estrogen and progesterone. Since pregnancy hormones have been implicated in both increase and decrease of cancer risk, establishing a mechanism would be essential to demonstrating a link between abortion and breast cancer, particularly given the absence of any good correlation evidence pointing in that direction.

ABORTION AND DEPRESSION

Psychology can be a more nebulous field than cancer research, and so data gathering for depression presents additional challenges. However, there is one advantage. Unlike cancer, whose risk rises with age, many mental illnesses emerge during youth and persist throughout the course of patients’ lives. When examining a proposed causative link between abortion and depression, researchers at least have the luxury of looking at what their subjects’ state of mental health was like prior to an abortion or pregnancy. Stunningly, numerous studies opt not to gather such data. A 2008 study published in The Journal of Psychiatric Research reported a connection between abortion and incidence of various mood, anxiety and substance abuse disorders.§ However, the authors only looked at mental health status after abortion. Despite having no data on subjects’ psychiatric condition prior to abortion, and thus no reason to even suspect (much less proclaim) causality, they felt comfortable writing that, “…abortion is responsible for more than 10% of the population incidence of alcohol dependence, alcohol abuse, drug dependence, panic disorder, agoraphobia, and bipolar disorder…”.

The New England Journal of Medicine recently published a more thorough study on the alleged link between mental disorders and abortion. Once again, Demark’s national registries supplied data that was free from the possible biases of self-reported information. The cohort study looked at “psychiatric contact” – a visit to mental health professionals – in 2 groups of women; those undergoing abortions and those giving birth. Data were taken both before and after these reproductive events. The population of women who had abortions showed no significant change in rate of psychiatric contact afterward, while group of women who gave birth showed an increase in psychiatric visits. The latter should come as no surprise, since postpartum depression and its rarer cousin postpartum psychosis are well documented phenomena. While the study found no link between psychiatric contact increase and abortion, it did show a greater overall incidence of psychiatric contact (ie. both before and after) in the women who had abortions than in women who gave birth. Had the authors only gathered data only from after abortions and births, they too could have reported a link between abortion and psychiatric disorders. But seen in full context, the data suggest entirely different possibilities; such as that depressed women may be more likely to seek abortions. This study should cast doubt on correlation studies claiming to find a link between abortion and mental disorders but failing to include before and after data on mental health.

The New England Journal of Medicine study has its problems too. It does not, for instance, include data on women who neither gave birth nor had abortions. Additionally, taking data from the national registry rather than through interviews, it has no way of even attempting to separate wanted pregnancies from unwanted ones. It has been suggested that what is potentially stressful to emotional health is not abortion but the experience of an unwanted pregnancy. Some studies focusing on three categories of women – abortion, birth and no pregnancy – have reported that while women who obtained abortions had a higher incidence of mental health problems, it was those who never got pregnant in the first place that were the most psychologically healthy. The fact that women who gave birth fell somewhere in between the troubled abortion group and the emotionally stable non-pregnant group, might suggest that some of these births were the result of stressful unwanted pregnancies. Or alternately, it could indicate that more emotionally stable women are less likely to become pregnant unintentionally. Ah, the vagueness of correlation studies.

WHEN WORLDS COLLIDE

Science journalists often report on interesting new findings that are far from established facts, but it’s hard to think of any other subject for which isolated and contested data is converted into policy. Doctors advise us not to smoke and to reduce our consumption of saturated fat, but they shy away from recommending a daily dark chocolate supplement or herbal remedies with no demonstrated efficacy in clinical trials, and the government has yet to instruct them to do otherwise. There is no demonstrated link between abortion and either breast cancer or depression, and no reputable medical organization claims that such a links exist. And yet multiples states have opted to jeopardize the doctor-patient relationship by forcing health care providers to be deliverers of political ideology disguised as the protection of informed consent.

At no point in my reading did I encounter any single perfect study that addressed all variables and decisively established or refuted either of the anti-choice movement’s purported health risks of abortion. But one wouldn’t expect to find such a thing. That’s not how medical research works. However, one might expect to find numerous, well-designed and reasonably consistent correlation studies pointing the way to further lab-based research on possible mechanisms. And one might expect that, during this period, the research would not be presented to patients as proven and indisputable truths. And one would certainly expect that doctors would not be required by law to lie to their patients about these un-established risks, and that patients would not be required to lie to their doctors that they accepted and understood the confusing misinformation given to them. In short, one would expect less politics and more science.

* If you already know everything there is to know about research methodology, I encourage you to skip this section. And if you know even less than I’m giving you credit for, check out this useful glossary compliments of The British Medical Journal.

† In case you’re wondering, the answer is yes.

‡ hCG is what pregnancy tests are checking for and is also the prime suspect in the cause of “morning sickness” during pregnancy.

§ The data were taken from National Comorbidity Survey (NCS) interviews conducted in the early 1990s.

Who told you this?

Guttmacher Institute website: www.guttmacher.org (U.S. abortion statistics)

National Cancer Institute website: www.cancer.gov/cancertopics/factsheet/Risk/pregnancy

Henderson, K. et al. 2008. “Incomplete pregnancy is not associated with breast cancer risk: the California Teachers Study.” Contraception 77: 391-396.

Michels, K. B. et al. 2007. “Induced and Spontaneous Abortion and Incidence of Breast Cancer Among Young Women. A Prospective Cohort Study.” Arch Intern Med 167: 814-820.

Reeves, G. K. et al. 2006. “Breast cancer risk in relation to abortion: Results from the EPIC study.” Int. J. Cancer 119: 1741-1745.

Melby, M. et al. 1997. “Induced Abortion and the Risk of Breast Cancer.” The New England Journal of Medicine 336: 81-85.

Jacobson, H.I. et al. 2010. “A Proposed Unified Mechanism for the Reduction of Human Breast Cancer Risk by the Hormones of Pregnancy.” Cancer Prevention Research 3: 212-220.

Munk-Olsen, T. et al. 2011. “Induced First-Trimester Abortion and Risk of Mental Disorder.” The New England Journal of Medicine 364: 332-339.

Coleman, P. K. et al. 2009. “Induced abortion and anxiety, mood, and substance abuse disorders: Isolating the effects of abortion in the national comorbidity survey.” Journal of Psychiatric Research 43: 770-776.

Dwyer, J. M. and Jackson, T. 2008. “Unwanted pregnancy, mental health and abortion: untangling the evidence.” Australia and New Zealand Health Policy 5: 1-6.

Lazzarini,, Z. 2008. “South Dakota’s Abortion Script – Threatening the Physician-Patient Relationship.” The New England Journal of Medicine 359: 2189-2191.

Jasen, P.2005. “Breast Cancer and the Politics of Abortion in the United States.” Medical History 49: 423-444.

Species of the Month: FEBRUARY

It’s not every month that I can showcase a recently-discovered species in this column. But February's featured organism is so hot-off-the-presses that had I been writing this article around this time last year, it would not have even been an option. The species effectively did not exist back then, despite having been observed decades prior.

More Than One Jellyfish in the Sea

Between 1999 and 2000, biologists noticed a copious quantity of large pink jellyfish in the Gulf of Mexico. Back then, the animals were presumed to be an occurrence of the already known Mediterranean species Drymonema dalmatimum. Nevertheless, they decided to take some of them back to the lab for closer inspection. Now, after 10 years of messy dissections and DNA analysis, researchers at the Dauphin Island Sea Lab have determined the jellies to be an entirely new species; Drymonema larsoni. Dubbed the “pink meanie” the marine creature made its official debut on the cover of the latest issue of The Biological Bulletin and is described in an article by Keith Bayha and Michael Dawson.

Familial Bonds

Part of what makes Drymonema larsoni worthy of the coveted cover photo is that this new species was different enough to cause the authors to name a new family – Drymonematidae – to host it, a taxonomical revision the likes of which the world of jellyfish has not seen since 1921. In case you’ve forgotten your taxonomy pneumonics, here’s the one I learned to help keep the order (pardon the pun) straight: King Phillip Came Over From Germany Saturday.* That translates into KPCOFGS, which represents Kingdom, Phylum, Class, Order, Family, Genus, Species. Standard binomial nomenclature labels an organism using just the genus and species names. At 3 names in, you can see why a family-level revision is potentially a bigger deal than just a new species.

A Few Words About Jellyfish in General…

Jellies are far less compartmentalized than our own species. Theirs is a minimalist lifestyle. They have no brain, no skeleton and they lack a specialized digestive system. The bell-shaped umbrella that characterizes jellyfish gets its structure from a gelatinous substance called mesoglea. Food enters and waste exists through the same gastrovascular cavity. Unlike true fish, jellies lack gills and oxygen instead diffuses through their thin skin. Having radial symmetry, they don’t even have a right and left side, just a top and bottom, from which long tentacles often dangle.

…and Pink Meanies in Particular

So far, written information about D. larsoni is scant. The Biological Bulletin article contains a great deal of detail regarding morphology†, but less on behavior or anything else you might understand without getting a PhD in marine biology. However, the few news blurbs I encountered were all quick to mention that pink meanies eat other jellyfish, specifically moon jellyfish. They’ve been observed impressively attacking jellies much larger than themselves. The pink meanies accomplish this by grasping the prey with their tentacles and digesting it using proteases secreted from tentacle-like features called “oral arms”. Tentacle number varies proportionally to the size of the bell (192 on average), but most of the D. larsoni specimens were found to have 4 oral arms. Other jellyfish, which often feed on plankton, digest their food using gastric filaments that line their gastrovascular cavities. These filaments were absent in D. larsoni, a loss that the authors attributed to the organism’s tendency to specialize in consuming other jellyfish.

The Name of the Rose

what it actually looks like

D. larsoni was named for the scientist Ronald Larson, who wrote about the jelly in 1987, before anyone even realized it was a separate species. The nickname pink meanie, of course, references the "blue meanies" in the appropriately-aquatic film Yellow Submarine. Some animals acquire multiple common names, but since these things are jellyfish, and relatively rare ones at that, there may not be much need for additional monikers. Like it or not, we may be stuck with this name.

* There are ample variations of this pneumonic – Kids Prefer Cheese Over Fried Green Spinach, for instance – some of which I can’t repeat here for reasons of decency.

† Velar lappets per octant, axial position of rhopalia, stotocyst length and width, etc. You can probably guess why I’m opting not to focus on such things.

People Get Ready

On Sunday October 30^th of 1938, in honor of Halloween, Orson Welles famously narrated a radio adaptation of H.G. Wells’ War Of The Worlds. Not all listeners tuned in punctually enough to catch the disclaimer offered at the commencement of the show. Apparently, hearing tales of a Martian invasion on the radio told largely in the form of mock news bulletins left some of these people confused and frightened, believing that our planet was actually being attacked by space aliens.*

In our current century, it is even more challenging to tell the difference between reality and parody, and so when a friend at work presented me with a Guardian article entitled, “Earth must prepare for close encounters with aliens, say scientists” it took a few minutes of research to conclude that it was not a satire, or at least not a completely fabricated one. The British newspaper’s sensationalized headline was (rather loosely) based on a 2010 discussion meeting held by the Royal Society.† The meeting provided the content for a recent themed issue of the society’s journal, The Philosophical Transactions of the Royal Society A, which bore the more demure title “The detection of extra-terrestrial life and the consequences for science and society”. Basically, it’s a very special what-if edition that speculates on the kind of effect knowledge of life on other planets might have on the societies, religions, etc. of our own planet. You see, it’s not that we’ve discovered aliens or think we’re about to discover aliens, it’s just that, hmm, it’s good to be prepared?

Does the Royal Society have anything newsworthy to say on the subject? It depends on your definition of newsworthy. The Guardian’s headline starts to make a bit more sense after reading Martin Dominik and John C. Zarnecki's introductory paper. Here we learn that there is a protocol for how to respond to the possible detection of extra-terrestrial life – approved by several international associations with lackluster acronyms who are somehow involved in astronomy – but that the protocol holds no legal power. The authors therefore suggest that the UN get involved.

Much debate revolves around whether attempting to contact extra-terrestrials is really such a good idea, with various other articles pondering the repercussions of such contact. The Search for Extra-Terrestrial Intelligence (SETI) has already been scouring the galaxy for half a century for electromagnetic signals, mostly radio waves. They haven’t found anything. However, if they did, earth would have to decide what to do about it. Furthermore, there is nothing stopping us from throwing out signals that might be detected by other faraway life-forms.

The paleontologist Simon Conway Morris devotes his article to speculating on what kind of life we might find on other worlds. Being rather fond of the idea of evolutionary convergence, Morris predicts that intelligent extra-terrestrials would be biologically similar to our own human species and that, given our propensity to violence, this is somewhat worrisome. The Guardian piece makes much of Morris’ suggestion that we, “prepare for the worst”, without noting how often he states that it’s more likely we are alone in the universe.

As would be expected in an issue devoted to what might happen if something else where to happen, Morris is not the only one buffering his argument with caveats. Nobody is making any grand claims about the inevitability of visiting or being visited by intelligent life-forms from other planets in the next decade. The authors of the introduction begin their conclusion with the sentence, “So far, there is no scientific evidence for or against the existence of life beyond Earth.” While the journal’s special issue may have some interesting philosophical arguments, there’s little scientific information to be gleaned from it, and certainly no news (recall that the actual meeting took place last year).

But does that really matter? 2011 has already seen a generous serving of questionable, news-that’s-not-actually-new stories fueled by online social networking sites. I hadn’t even finished sorting through my post-holiday emails at work when I heard the shocking tale of bird deaths in Arkansas. The feathery corpses were attributed to everything from chemical pollutants to the coming apocalypse. Gradually the story that emerged was something conservationists have know for ages; lots of birds die, every year, often by such banal and non-menacing methods as flying into windows. Similar events probably occurred last year as well, it’s just that your mom wasn’t on Twitter back then.

And then there was the zodiac fiasco. Earlier this month, astronomy instructor Parke Kunkle caused an unexpected stir when he revealed, during an interview for the Minneapolis Star Tribune, that our view of the constellations during any given month has been gradually shifting throughout the several thousand years following the establishment of our current zodiac signs. Of course, this was only news to those with less knowledge of astronomy than a student taking an introductory community college course on the subject, which apparently is most of us. Much panic ensued. Suddenly everyone was having identity crises over their incorrectly-assigned, zodiac-based personality traits, and those unfortunate individuals born between November 30^th and December 17^th were coming to grips with the possibility of being born under a sign named after a thirteenth constellation; Ophiuchus. With astronomers everywhere shrugging and saying, “What? What’s the problem here?” astrologers had to step in and do some speedy damage control to calm the distressed and disheartened public.‡ 

Frankly, I’m a little surprised the Guardian’s space alien article didn’t cause more mayhem, or at least a few ripples of hype. It took me several searches to coax Twitter into telling me anything at all about the would-be scandal, but then I was using big words like, “extra-terrestrial” and “Royal Society”. What finally did the job was “Guardian aliens”. The posts didn’t seem especially alarming. Most just provided a link to the article along with one of its more over-the-top quotes. Perhaps society is getting savvier in processing its non-news. Who knows, if we weather enough horoscope restructurings, maybe we’ll even be ready to handle extra-terrestrial life when/if the Royal Society has some actual news to deliver. Maybe. But probably we’ll freak out.

* The actual degree of panic caused by Welles’ show is now said to have been largely overstated by journalists of the time, but it’s an amusingly-exaggerated tale so I won’t bother to cast any further doubt on its veracity.

† Short for The Royal Society of London for Improving Natural Knowledge, established 1660. Isaac Newton was their president for over 20 years, so they’re pretty legit. The group’s journal is divided into two publications; A, for physical, mathematical and engineering sciences and B, for lowly biology.

‡ Fear not, your horoscope is even less tethered to actual science than you previously believed. Unless you’re into something called sidereal astrology, your zodiac sign is based on sets of dates named after constellations rather than the periods in which those constellations are visible. I’m still an Aries. You’re still whatever it is you are. It’s going to be okay.

Hot Topic

For a city not known for its winters, Austin has been putting in a good effort this week. Daytime highs are struggling to get above 40ºF and nighttime lows have dipped to temperatures I would prefer not to discuss. It’s cold out there. I plan to make soup later this evening, as few things in this world taste better than a big bowl of soup on a freezing January day. Probably I’ll opt for gazpacho, because nothing compensates for the brutality of winter like a heaping serving of raw puréed tomatoes mixed with seasonings and then chilled….Did I lose you? Were you hoping for hot soup? Well you’re not alone in your preferences. Though I’ve not yet been to Spain, I’m told that it’s difficult to find a bowl of gazpacho during frostier months, the reasoning of restaurateurs being “what lunatic would want to eat cold soup in the middle of winter?” But not everyone agrees that winter gazpacho is such folly. Raw foodists, loosely defined as those who consume 75-100% of their food uncooked, would readily choose cold soup over boiled minestrone, arguing that the former is nutritionally superior. Raw food is a growing and lucrative branch of the restaurant business (as demonstrated by the exorbitant price of my favorite Daily Juice smoothie) but supporters of broiling and barbequing aren’t swayed by the sales pitch. It was one of these individuals that brought to my attention the belief that cooked food was instrumental in human evolution. “I don’t get these raw food people,” My source lamented “Don’t they know that eating cooked food is what allowed us to develop larger brains than other animals?” This alleged knowledge was news to me, but as my boyfriend would say, the idea “Googled well”* and so here we are….

Heat Wave

Here is the claim in a (dry roasted) nutshell: humans have a larger brain, relative to body size, than other mammals. Large complex organs are energetically costly to maintain, and yet our species’ basal metabolic rate † is not significantly higher than that of similarly-sized animals with smaller brains. Since higher metabolisms are not fueling our enormous brains, the additional energy required for such stately organs must be coming from somewhere else, and that somewhere else, according to certain biologists, is a decreased gut size. ‡ The human gastrointestinal tract is about 60% smaller than expected for a primate of our size. Supporters of the “expensive-tissue hypothesis” believe that the innovation of cooking, which increases the available calories in plant-source foods, drove this important change in our anatomy.§ Over time, they argue, with less effort needed to digest tough fibrous vegetation, the gut shrank and the brain grew, eventually yielding the dimensions of our current species, Homo sapiens. Furthermore, because of these changes, it is now difficult for us to obtain enough energy (calories) from raw food sources alone.

You Can’t Start a Fire Without a Spark

If you heard a supporter of this hypothesis speak on the subject, they might present it as though it were a given, possibly a launching point for another argument. But the idea is far from universally accepted. One problem is that scientists don’t agree on how long humans and their ancestors have been able to control fire. Some estimate that the technology arose about 250,000 years ago, some 600,000 and others have suggested dates as far back as 1.9 million years. This is a rather important detail to sort out. Homo sapiens as a species is purported to have been in existence for only about 200,000 years. Cooking, and thus fire, would need to predate this considerably if it is to be the accepted cause of our being the smartypants species we are today.

Previous connections between diet and physical proportions have focused on the adoption of meat consumption. While meat is more difficult to chew in its raw form (and more likely to be teeming with bacteria), the availability of its calories is not strongly affected by cooking, which makes this hypothesis less dependent on the ability to get a campfire going.

Other critics have cited non-human species that have smaller guts or higher metabolic rates and yet have failed to develop large brains as evidence that the connection between these elements is not an obvious one.

Smoke and Mirrors

Meanwhile proponents of raw foodism, avoiding all this evolutionary biology nonsense, maintain that cooking food removes valuable nutrients and replaced them with various toxins. They’re right, of course, to some extent. We’ve all heard before that the delicious charred stuff on grilled vegetables (and meat, if you’re into that) and toasted marshmallows contains carcinogens. Additionally, as any raw food website will cheerfully inform you, cooking creates dietary advanced glycation end products (dAGEs) which are believed to contribute to maladies such as diabetes and cardiovascular disease. However, the increase** in dAGEs varies among food types and cooking techniques. Meat is more affected by heating than are vegetables, and high temperature/low-moisture cooking environments have the greatest potential for harming food items of either ilk. In terms of dAGEs, boiling is not such a big deal, and a crock pot is barely worse than a dehydrator (though I still refuse to purchase either of these silly devices).

It bears mentioning that certain vegetables are toxic in their raw form. Recently, I helped to prepare taro root, a tuber unfamiliar enough to necessitate Internet research in order to cook. It turns out that taro is not only inedible when raw (calcium oxalate) but that it really shouldn’t even be touched with bare hands until it has at least been microwaved, as it makes some people’s skin itchy. Other raw items to avoid adding to your salad in mass quantity include parsnips, kidney beans, buckwheat greens and, of course, raw chicken, tempting though it may sound.

Too Many Cooks

A major downside of trying to figure out what happened thousands and millions of years ago is that we can’t actually do experiments to confirm our hypotheses. We can argue about interpretations of the fossil record, but we can’t just retreat to the lab and subject animals to similar conditions for a few millions years to observe what happens. Nobody has that kind of funding. Most educated people accept the theory of evolution by natural selection, but specifics of cause and effect along the road to the present are difficult/impossible to prove. It may be fun to speculate about possible explanations, but there’s no getting around the fact that we weren’t there. Multiple hypotheses exist for numerous anatomical quirks. For instance, the existence of lactose intolerance after weaning in some populations has been attributed to more than one possible causative factor. One argument states that the loss of the lactase enzyme is simply another limited energy issue; why continue to produce the enzyme if there was no use for it in the pre-agricultural era. But another argument attributes the discarded enzyme to the “parent-offspring conflict” – the idea that parents, who wish to reserve enough resources to produce more than one child, have different goals than their children, each of which cares only for its own survival and would gladly postpone weaning indefinitely if it were enzymatically possible. Which hypothesis is correct? I have no idea. Just pick your favorite viewpoint and hope for the best.

What’s For Dinner?

One way of testing at least part of the expensive-tissue hypothesis, the idea that humans now lack the ability to get enough energy from uncooked food, would be to see if anyone can thrive on a raw food diet. This is harder to establish than you would think. Not a lot of studies have been done on the subject and, as with so many human health studies, they are correlation studies rather than laboratory experiments. The subjects in articles on raw foodism are people who chose this diet rather than having it randomly assigned to them in double-blind controlled study. Some studies have found that certain nutritional deficiencies exist in those adhering to raw food diets. Low B-12 levels and low serum HDL cholesterol (the “good cholesterol” you often read about) were observed in one study. Another reported low body weight and lack of normal menstruation in women. Also bothersome is that fact not that many people eat a 100% raw diet (thus the 75-100% guideline for qualifying as a raw foodist). To my knowledge a long-term study on humans consuming exclusively raw foods has yet to be done.

But would a diet of entirely cooked food be a good thing? While cooking may have helped our ancestors get enough calories in times of scarcity, most of us live in quite different conditions today. Easy calories abound and humans are now more likely to be malnourished than undernourished. The deficiencies in consumers of mostly cooked foods are vitamins and fiber, a problem that has been linked to more diseases than I have the patience to list. The same article that reported low HDL cholesterol levels in raw foodists also reported low LDL levels (aka “bad cholesterol”) in the same subjects. Cooked starches and meats may be a fine way to avoid starvation, but they don’t necessarily promote longevity. Recall that for an adaptation to succeed it need only help its bearers live long enough to produce and raise offspring. Fitness in old age is a luxury of modernity.

So, as is often the case, the best route might be a compromise between two extremes. A varied non-partisan diet of cooked and raw foods may be the most sensible solution to our dining dilemmas. Soup and salad rather than soup or salad.

* More novel slang for you. To “Google well”, means to garner enough hits when typed into one’s search engine to merit further investigation. It can also be used in the negative to express skepticism when receiving information second hand, “That doesn’t sound like it would Google well.”

† Basal metabolic rate is the minimum amount of energy required by an organism just to sit still and not die (running around costs extra). It is higher in mammals like ourselves than in retiles due to our sophisticated physiological methods of thermoregulation.

‡ The crude term “gut” refers to the alimentary tract, which includes the stomach as well as the various portions of the intestines.

§ The cell walls of plants are made of the polysaccharide cellulose, which is a real pain to break into smaller molecules. Cows have bacteria-produced enzymes to accomplish this, but humans are less fortunate. However, heat can also break cellulose into smaller, more digestible units.

** dAGEs exist in raw foods as well and are especially high in meat.

Who told you this?

Wrangham, R. and Conklin-Brittain, N. 2003. “Cooking as a biological trait.” Comparative Biochemistry and Physiology 136: 35-46.

Aiello, L. and Wheeler, P. 1995. “The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution .” Current Anthropology 36: 199-221.

Krebs, J. R. 2009. “The gourmet ape: evolution and human food preferences.” American Journal of Clinical Nutrition 90: 700S-711S.

Pennisi, E. 1999. “Did Cooked Tubers Spur the Evolution of Big Brains?” Science 283: 2004-2005.

Gibbons, A. 1998. “Solving the Brain’s Energy Crisis.” Science 280: 1345-1347.

Uribarri, J. et al. 2010. “Advanced Glycation End Products in Foods and a

Practical Guide to Their Reduction in the Diet.” Journal of the American Diabetic Association 110:911-916.

Garcia, A. L. et al. 2008. “Long-term strict raw food diet is associated with favourable plasma b-carotene and low plasma lycopene concentrations in Germans.” British Journal of Nutrition 99: 1293–1300.

Koebnick, C. et al. 2005. “Long-Term Consumption of a Raw Food Diet Is Associated with Favorable Serum LDL Cholesterol and Triglycerides but Also with Elevated Plasma Homocysteine and Low Serum HDL Cholesterol in Humans.” The Journal of Nutrition 135: 2372–2378.

Koebnick, C. et al. 1999. “Consequences of a Long-Term Raw Food Diet on Body Weight and Menstruation: Results of a Questionnaire Survey.” Annals of Nutrition & Metabolism 43:69-79.

Species of the Month: JANUARY

In some ways “Species of the Month” was not the best choice of titles for this column. I could have saved myself some headaches by opting instead for the term “life form” or “organism”. The decision wasn’t entirely arbitrary. After all, I wanted to be able to provide you with the exciting Latinized binomial nomenclature for these plants/animal/fungi/etc. But as a result, I now find myself discussing a creature that is essentially a subgroup of a common species.

Black is the New Gray

Black squirrels are melanistic versions of the species Sciurus carolinensis – the eastern gray squirrel. Aside from their dramatic pigmentation, they’re just like the fairer-haired members of their species. Their lifestyles are probably similar to the squirrels in your own neighborhood.* They live in trees, eat nuts and make those squirrel sounds at you when you’re leaving for work in the morning. They are “scatter-hoarders”, which means they bury food they wish to store for later in numerous locations rather than in one or two well-guarded caches. Sometime they bury their leftovers in your outdoor potted plants, uprooting a perfectly good basil plant in the process. For this and other similar offenses, squirrels are often viewed as pests by humans. As with the eastern grays, black squirrels occupy portions of the Eastern and Midwestern United States, as well as Southeastern areas in Canada. I recall seeing them in Manhattan’s Union square Park on more than one occasion (though it’s also possible that the animals I observed were merely gray squirrels with a heavy coating of soot.) And, sometime during the past century, the black squirrel found its way to the British Isles

Controversy From Across the Pond

Great Britain has its own native species of squirrel, the red squirrel (Sciurus vulgaris), and they were not pleased when our gauche American gray squirrels escaped into their British countryside (after being introduced in captivity by some thrill-seeking noble) and largely out-competed the dainty red squirrel. In recent years black squirrels, whose presence in the wilds of the UK also resulted from captive-living mishaps, have grown in population and now threaten to outnumber even the country’s detested gray squirrels. Much indignant speculation as to the cause of the demographic shift ensued in the British press. A 2008 article in The Daily Mail claimed that the “mutant pack of black squirrels” were nudging out grays as a result of a higher levels of testosterone conferred by the pigment mutation (I’ve yet to find any documentation of hormonal variations between the differently colored squirrels). Black squirrels are often described as being more aggressive, though this is based on anecdotal observation, and perhaps a dash of xenophobia. The less sensationalistic BBC wrote that black squirrels were increasing in number simply because the mutant gene responsible for their pigmentation was dominant over the wild-type allele. This is partially accurate, or perhaps “incompletely” accurate.

Incomplete Dominance

In 2009, British scientists finally rounded up some squirrels and attempted to sort out what was going on in terms of both genotype (actual genes present) and phenotype (outward appearance of the animal). They concluded that there were three, not two, coat variations among Sciurus carolinensis. In addition to the black and gray squirrels there exists an in-between phenotype; a brown-black squirrel with an orange underbelly (as opposed to the white underbelly of the original gray squirrel). Genetic testing showed these phenotypes to correspond exactly to differences in a singles pair of alleles. † Using E⁺ to indicate the wild-type allele and E^b for the melanic allele, the authors demonstrated that the mutant version was incompletely dominant over the wild-type. That is, squirrels with two E⁺ alleles had the familiar eastern gray coloring, squirrels with two E^b alleles were entirely black, and those with one of each allele exhibited the mixed, brown-black phenotype. Complete dominance of the mutant gene would not yield this in-between squirrel variant. If the E^b allele were dominant, even the heterozygous animal (E⁺ E^b) would be all black.

Genotypes left to right: E⁺ E⁺, E⁺ E^b and E^b E^b

Why All the Black Squirrels Then?

If black squirrels don’t posses a quickly-spreading dominant gene or any demonstrated hormonal/behavior advantage, then what might explain their rising numbers in the UK? Again Britain’s favorite tabloid has a thought; sexual selection. Surely stirring discomfort amongst pale English readers throughout the country, The Daily Mail suggested that female gray squirrels prefer to mate with black squirrels. However, as with claims of the blacks’ bullying barbarism, rumors of their greater success with the ladies is thus far only hearsay. If one counts the brown-black mixed squirrels as black squirrels, then the combined animals could eventually outnumber grey squirrels by gene prevalence alone. But, of course, there are always other factors to consider. Even the folks who sequenced all that squirrel DNA don’t rule out the possibility that additional genes may be involved in making grey squirrels black. It’s frontier science. If you really want to know the answer, you’ll need to get yourself some squirrels, a microscope and a bunch of expensive DNA materials. Let me know if you find anything interesting.

* If you live in Austin, you’re probably in the company of fox squirrels (Sciurus niger). New Yorkers are more likely to see eastern grey squirrels. And the rest of you will have to do your own research if you wish to learn what rodents inhabit your vicinity.

† A quick introductory genetics recap: Alleles are different versions of a gene, each occupying the same spot (locus) on one of two chromosomes. One chromosome (and thus one allele for the gene of interest) is inherited from each parent.

The Light Side of the Road

Since I don’t own a scale, I can’t tell you exactly how much my bike weighs. But rest assured, it is heavy. It’s a secondhand steel-frame model purportedly manufactured by Sears department store, probably in the 1970’s. Friends complain of its unwieldy mass (particularly anyone hoisting it onto their car’s bike rack) and more than one person has suggested “upgrading” to something more modern. But I’ve bonded with the vehicle and strive to paint it in a positive light. Sure, it sucks carrying the behemoth up a flight of stairs to shelter when it rains. But overall, it’s a solid bike. Sturdy and hardworking. “And a comfortable ride too”, I tell the skeptics, “not like those flimsy featherweight carbon-frame bicycles that retail for ten times as much.” And so I eagerly put aside any ambitions of doing a year-end top ten science innovations/headlines/etc. list (you’re surely as sick of them by now as you are of holiday cookies) to report on this merry little piece from the British Medical Journal's Christmas edition, in which an anesthesiologist attempted to determine if the newer, lighter bikes had any advantage over their clunkier predecessors.

Being fortunate enough to have two bicycles available for his daily commute, the good doctor designed a simple experiment to examine which of the bikes was the more efficient way to get to work. Over a 6-month period, (winter to summer) he chose his bike for the day by flipping a coin. The riding time for each round-trip journey, as well as the top speed, was recorded by a bicycle computer. During the experimental period, Dr. Groves made 30 trips on the steel-frame (809 miles) and 26 trips on the carbon-frame (711 miles). * At the end of month 6, he totaled the data and, wouldn’t you know it, the older, heavier steel bike fared no worse than the shiny new one, which had been purchased for what is almost a month’s salary to an average person without an MD.

The author discusses several physical forces that can affect the cyclist; rolling resistance, drag and gravity. Rolling resistance (the friction encountered by round objects, such as bike tires, moving on a flat surface) is minimal on paved roads, so the additional work needed to overcome it is slight. The effect of drag (aka air resistance) on the cyclist is significant. However, drag is an odd force. It is independent of mass and instead varies relative to velocity. More velocity results in more air resistance. † It’s a drag, but not any more so on a heavier bike. This leaves gravity as the most relevant consideration. As you may vaguely recall from your first semester of physics, more work is needed to push a bike with greater mass up a hill. But since a round-trip commute can’t actually be all uphill both ways, things should even out a bit as you coast downhill. Unless, of course, you were crazy enough to purchase a fixed-gear bicycle.

On average, Groves’ commute was about 7 minutes shorter in summer than in winter. He attributes this in part to the poorer weather and bulkier clothing that plague winter cycling, but he also mentions that greater caution taken to avoid falling on the ice and snow may be an additional slowing factor. This raises an interesting question. Was the upper speed limit in the summer months a result of the physical limitations of how fast the rider could propel his bike, or merely the highest speed at which the rider could safely control the bike. If it was the latter, then one of the bikes might be less efficient and the rider may just be working harder to achieve the maximum comfortable riding speed on that vehicle. The author made no mention of whether he felt a greater desire for a cold alcoholic beverage following commutes made on the steel bike.

It’s understandable then if you still feel that a lighter bike would be easier to peddle. But keep in mind that you’re also hauling your own weight up those hills. Groves’ steel-frame bike was about 9 lbs heaver than his carbon-frame (the bikes were about 30 lbs and 21 lbs, respectively). This looks like an impressive weight difference until you add to each bike the weight of its rider. Couple this the frequently-made observation that lighter bikes are less comfortable (rumor has it one feels the bumpy road more on the newer bikes), and it’s hard to justify paying more money for less mass.

To be fair, I should note that the author of the bicycle paper does not claim that his single-subject study is a conclusive and exhaustive exploration of the subject. My willingness to generalize his findings to all bicycles on both sides of the Atlantic is a result of the human tendency to gratefully accept any data that supports one’s existing conceptions. ‡ I like my bike and have no plans to get a newer, lighter one. And as far as I’m concerned, there is now medical literature to back me up.

* That’s 56 total trips, so either he doesn’t work a 5-day week or he used other means of transportation more than half the time.

† This makes sense when you think about it. On a reasonably calm day, the “wind” blowing at you as you ride the bike is created by the forward motion of the bike. The faster you go, the windier it feels.

‡ That’s confirmation bias, for those with a fondness for psychological terminology.