Bang!

When I first saw this video I was positive that it had to be a clever hoax but, I'll be damned, the Pistol Shrimp really does exist!

And here's a link to the science behind it.

Unstructured Pharyngea

One of the freakier things about H.R. Giger's design of the Alien (from the movie of the same name) was that weird set of inner jaws that the alien had which would snap out at you when it got close.

The technical term for these sorts of second jaws are pharyngeal jaws. Such jaws actually do exist in nature, but, before now, no one had observed a set of pharyngeal jaws that could actually move independently of the outer jaw (they tend to be more like a second row of teeth). Recently, however, scientists have discovered that moray eels actually do have a pharyngeal set that do work something like the one's that the Alien has.

Let us hope that the rest of Geiger's more creative speculations remain in the realm of fiction.

---

Thanks to Arturo Magidin for pointing me to the NPR link

Unstructured Coolness

The one thing about Creationists that I can understand is the tendency to be overwhelmed by the complexity and beauty of the natural world. There is an understandable temptation to throw our arms up in the air and declare that it simply can't be the result of unthinking processes.

The problem, of course, is that it doesn't do to answer one mystery by positing yet another, even larger mystery. This is particularly the case when we attempt to account for something of finite complexity and comprehensibility with something that is supposedly infinitely complex and incomprehensible.

Be that as it may, the inner workings of a cell is one of those things that tugs at our intuition and which strains us to suspend disbelief. I think that it is no coincidence that the proponents of Intelligent Design love to harp of the workings of cellular biology so very much.

Today's link is to a video that shows those workings with some truely vibrant animation. It should be stressed that a few liberties were taken in order to be able to actually show anything at all (real cells are very crowded places that don't lend themselves to visualization) but that the essential scientific accuracy of the images are intact.

By the by, that funny little walking thing, towing a vesicle, is a kinesin and they really do walk much like they are portrayed as doing.

Sit back and be amazed.

Mike, the Headless Chicken

It is said that truth is stranger than fiction. Well, I read a fair amount of rather strange fiction, so I'm not generally inclined to accept the saying without good evidence to back it up.

Sometimes, however, reality does live up to the aphorism. Here is the tale of Mike, the Headless Chicken.

Unstructured Ants

The University of Berkeley News has a really fascinating article on a species of ants that can glide. The ants are wingless but use their bodies to direct the flow of air around them so that they can control their direction while falling. This is a useful ability for this particular species because they live high up in a forest canopy. By controlling their fall, they can steer themselves back towards the trunks of their own trees and return to their own branches, ususally within ten minutes.

In addition to the subject of the ants, themselves, the article provides a good illustration of how discovery and research work in the sciences.

There's some amazing video that goes along with the article, too. Unfortunately it's in the RealPlayer format, which is definitely not my preferred media, but you really need to see these ants in action to genuinely appreciate how amazing this is.

The Tree of Life

One of the goals of science is to find theories that provide unifying frameworks. In physics, Newton's Theory of Universal Gravitation unified the heavens and the Earth by showing that the same forces that goverened terrestrial matters also applied to the extraterrestrial. Physics is, however, still in search of a grand unifying theory that accounts for all forces via a single equation that can, in principle, explain all physical interactions. Many disciplines lack even basic unification. We don't, for example, have a grand congitive theory (which is not to denigrate the accomplishments of cognitive scientists who are, after all, dealing with an extremely complex subject).

In all of the sciences, the best example of a unifying theory is Darwin's Theory of Evolution. It is a shame that Darwin's magnificent theory does conflict with a number of religious dogmas. It is not the first time that this has happened. The Catholic Church famously rejected the Copernican Theory of Heliocentrism, Christian Scientists, to this day, reject the Germ Theory of Disease, and there are even groups that reject, on religious grounds, the Theory of Sphericalism when interpreting the shape of the planet. It is my hope that the current furor over the Darwinian model will, too, die down in the fullness of time. Be that as it may.

Although the theory has been updated somewhat (i.e. the Modern Synthesis) by the integration of genetics and elucidated by such things as Game Theory, Darwin's central insight into the mechanism by which new species of organisms arise remains simultaneously elegant and profound. Darwinism also implies a different sort of unification by demonstrating the profound interconnections between all living organisms. I've already spoken of this in my prior essay titled Immanence; however, this time I'd like to draw attention to a site that beautifully illustrates these interconnections.

This is the Tree of Life web project. The Tree of Life site is, essentially, a gigantic database of the connecting nodes (e.g., generas, phylums, etc) of life on this planet. This description, however, fails to give a sense of how beautifully the site is organized nor of the depth of information that is provided at each node (to say nothing of the plethora of beautiful photographs and illustrations). This also fails to give a sense at the sorts of surprises that one can find (for instance the observation that crocodiles are more closely related to birds than to turtles, overturning our traditional conception of what it means to call something a reptile). It is the sort of site that begs you to pick a starting point and to simply wander through it. I have lost (or, rather, found) hours of time doing just that. I hope that you shall, too.

Once you've had your fill of the site (as if!), I might also encourage you to go out and buy Richard Dawkin's new book The Ancestor's Tale, which expands on these interconnections via a brilliant "prilgramage" backwards in time to meet up with our "concestors".

A Rebuttal to the A Priori Argument Against a Genetic Basis for Homosexuality

In recent years there has been a lot of hoopla as a seemingly endless list of genes "for" various things have been reported. We have heard that there are genes for obesity, genes for depression, genes for reading ability and all sorts of other behavioral traits. One of the more controversial claims has been claims that a gene for homosexuality has been discovered.

Much of the controversy is scientific. It is notoriously difficult to accurately map human behaviors to genetic components and there have been methodological challenges to this claim. This is, ultimately, an empirical question with a great many complicating factors and methodological hurdles. The scientific community has not reached a consensus on this claim and it is unlikely that any consensus will be reached in the near future.

It is not the purpose of this essay to address the scientific question. I will leave that to the experts. Many of the objections, however, are not scientific. One objection, in particular, attempts to make an a priori argument against the very possibility of a so-called "homosexual gene" using a spurious evolutionary argument. The argument can be aptly summarized by the claim that any homosexual gene would have disappeared from the population long ago since homosexuals don't reproduce.

On the face of it, the argument seems convincing. As far as genetics is concerned, there is no difference between dying in your crib and being a childless person who lives to the age of a hundred. So long as you fail to reproduce, your body is a genetic graveyard. Since homosexual sex does not result in offspring, it would seem logical, then, that homosexuality would have been bred out of the populace. I will demonstrate that there are several flaws with this argument.

The first problem is that homosexuality does not preclude the possibility of reproductive activity. In modern times, homosexual individuals can have children by utilizing a variety of technological solutions. Gay men can donate their sperm or find a surrogate mother. Lesbian women have a variety of in vitro and in utero options. Beyond that, there is nothing that physically prevents homosexuals from engaging in heterosexual acts. Indeed, in social climates where homosexuality is criminalized or where there is strong social pressure to conform to heterosexual norms, it is not at all uncommon for homosexuals to conform to heterosexual norms up to and including marriage and parenthood. In such a climate (which has been sadly common throughout history), even if the view of genetics that this argument projects were to obtain, any hypothetical genes for homosexuality would have few barriers to propagation. That said, the a priori argument does employ a naïve understanding of population genetics.

For the basis of this examination, let us consider a hypothesized homosexual gene to be reproductively deleterious (this isn't necessarily the case, but we'll return to that point later). It is critically important to stress that such an evaluation is not a moral judgment but, rather, a neutral statement that only pertains to the reproductive impact that such a hypothesized gene would have. In order to assist our efforts to think of this subject in morally neutral terms, I will not discuss how a gene for homosexuality could propagate itself in a population. I will, instead, discuss a hypothetical S gene that results in sterility. In point of fact, there are a variety of genetic conditions that lead to sterility but, for the purposes of this essay, they can all be subsumed under the common label.

How can a gene which compromises reproduction spread through a population? It would seem that the very first instance of the gene should eliminate itself through an act of genetic suicide. This would only be the case, however, if the presence of a gene invariably resulted in the physical expression of that gene. The technical terms for an organism's genetic structure is its "genotype". The term to describe an organism's physical structure is its "phenotype". Genotype does not equal phenotype. At best, an organism's genotype is an indicator of that organism's phenotype. Simply because I have the S gene, however, does not mean that I will necessarily be sterile.

How can this be? There are several reasons that this could be the case.

The first reason is that there are two different varieties of gene: dominant and recessive. A given gene will occupy a particular location on a chromosome called an allele. In humans (and most other organisms) each allele is occupied by a pair of genes with each half of the pair being inherited for each parent. A given gene will always have a phenotypic expression (meaning that it will be physically manifested) if it is dominant. A recessive gene, on the other hand, will only manifest if it is present in both slots of the allele.

To take a classic example, we'll use a gene for Brown eyes (designated with a capital B) and blue eyes (designated by a lower case b). Let us say that you have double-dominant set of genes for brown eyes (BB) and your partner has the double-recessive genes for blue eyes (bb). Let us further suppose that you have four children. Statistically, your children will receive the following gene combinations: Bb, Bb, bB, bB. Because brown is dominant, all four children will have brown eyes; however, each of them will carry a gene for blue eyes.

Let us suppose, now, that one of your children (Bb) marries a person who also have a dominant brown gene and a recessive blue gene (Bb). Statistically, your children will receive this combination: BB, Bb, bB, bb. Only the child with the bb gene combination will have blue eyes (although an additional two children will continue to carry the recessive genes for blue eyes.

If sterility were to be carried on a recessive gene, it could persist in the gene pool indefinitely in spite of the fact that it conferred a reproductive disadvantage. It is important to stress that, even though it would be allowed to persist, there would a critical population threshold above which an anti-reproductive gene would be selected against. Scandinavians are famed for having blue eyes. This is because their population has an abundance of the recessive genes that confer blue eyes. Since there is no reproductive disadvantage, such a bias in population is allowed. You would not, however, expect to find an equivalent population where an S gene had a majority representation in the populace.

There is, however, one way that an S recessive could positively leverage itself into future generations. This is via the mechanism of kin selection. The easiest way for a gene to get into the next generation is directly. This is why the sex instinct is so strong. When we have children, each child carries 50% of our genes into the next generation. So what happens if we can't have children? The solution is that we turn to our relatives. If you have brothers and sisters, each of them also has a 50% genetic relation to you. Any nephews or nieces you have will have a 25% relation. This isn't as high as your own children would be but, if you can't have children of your own, any additional assistance you could provide to your siblings to help them raise your nephews and nieces will be to your genetic advantage.

The elegant thing about this supposition is that we don't have to even suppose that the S gene would directly encourage you to devote your efforts to your sibling's children. So long as you have a general instinct to expend more effort on your closest relatives when you, yourself, are reproductively disadvantaged, such an instinct would be positively selected for. After all, genes aren't the only reasons one may be unable to reproduce. Circumstances alone (e.g., accidental castration) guarantees that a certain percentage of any given generation will be unable to reproduce regardless of genetics. As such, a kin assistance instinct would represent a good genetic strategy regardless. If humans do have such an instinct (and it must be stressed that this is speculative), any sort of recessive S gene would automatically result in efforts to assist non-manifesting copies of itself in near relatives even if the S gene were entirely deleterious for the individual who was carrying it.

Beyond this, the simple "pea pod" Mendelian model, where a single set of genes accounts for all of the genetic variance in a population, is, itself, typically an oversimplification. There is not, for instance, a single tall gene and a single short gene that determines whether one is short or tall. In reality, height is determined by a complex of different genes interacting in tandem (along with a variety of environmental factors, but let's not get ahead of ourselves). This is how things work in most cases of phenotypic expression. Instead of P = G (for every phenotype there is one and only one gene), P = G1, G2, G3… (for every phenotype there are multiple genes). Because of this, it is possible for certain combination of genes to result in anti-reproductive outcomes (e.g., sterility or premature death) while other gene combination are either neutral or reproductively advantagous.

Let us suppose, for the sake of argument, that sterility expresses itself only when four particular genes manifest. Let us further suppose that these four genes have reproductively beneficial manifestations when teamed up with most other alternative sets of genes. In such a schema, not only could these genes persist in spite of the occasional drawback of producing a non-reproducing individual but they could, in fact, be positively selected for because the majority of the time they would give a reproductive advantage to the person that they would find themselves in.

This is a bit like playing an odd game of poker where four aces result in a busted hand. Two aces or three aces would still make for a good hand (as would aces and kings or the aces in a full house, a straight or a flush). Even though four aces would be a "bad" hand, any other combination would be desirable and advantageous.

Beyond this, the path from gene to phenotype is not inevitable. The way that genes "build" bodies is through the production of proteins (with the help of RNA). Every gene encodes in the instructions for building a particular protein. Between the production of proteins and the production of bodies, there are a number of critical steps. During fetal development, various chemical cascades are turned on or off or modified according to the activation and deactivation of various chromosomes. This is a complex process that can often be very fuzzy. This is the reason that geneticists rarely say that gene X determines phenotype Y. Rather, they may say that particular genes result in a predilection for the presence of certain phenotypes. The predilection may be strong or weak but it is rarely absolute.

Take sex as an example. Most of us have been taught that boys have a Y chromosome and that girls don't. In the vast majority of cases, this is true. It is not, however, inevitable. Even discounting intersexual births (where a child is born with indeterminate genitalia) it is possible for a child with a Y chromosome to be born a female and, likewise, for a child who has two X chromosomes to be born a male. In most children, the Y chromosome signals the activation of testosterone production at a critical junction of fetal development. In some births, the signal either fails to go off (a false negative) or it goes off spuriously (a false positive).

If something as strong as sexual determination can only be considered a strong statistical likelihood, it should not surprise us that something as subtle as a behavioral gene could be present without manifesting itself. Even if the supposed S gene were dominant and even if it always resulted in an absence of reproduction when manifested, it would still be possible for non-sterile individuals to carry it forward into the next generation. If there was only a weak predilection, this would actually be the expected case.

Nor do potential environmental impacts end at the womb. Take left handedness as an example. Handedness is believed to have a strong genetic component. Never the less, for years left handedness was considered to represent a kind of moral failing (hence the word "sinister" which is a Latinate form of the word "left"). Because of this immoral reputation, children who exhibited left handed behavior were often sternly corrected (typically with a ruler) and encouraged to use their right hands. Such efforts did not always produce right handed behavior but the success rate (if we can use the word success in reference to such a practice) was sufficiently high that the practice remained in vogue for many years.

Environmental effects do not have to be coercive, either. Consider a predisposition to obesity. Even though an individual may have such a predisposition, it may not manifest itself unless they are exposed to certain foods or dietary conditions. A person with a predisposition to melanoma may not develop skin cancer unless they are exposed to greater than average amounts of UV radiation. Indeed, some genetic predispositions may only manifest spontaneously and at random. As such, perhaps only 25% of individuals with the S gene would actually become sterile (and, then, perhaps only the ones that have consumed high quantities of beta carotene or been exposed to high levels of environmental arsenic).

As we can see, even though it seems intuitive that a gene which would cause sterility would eliminate itself from the population in short order, the truth is that there are a multitude of avenues whereby it can find its way into further generations. Exchanging our S gene for a homosexual gene (or gene complex), we can see that a priori arguments that propose to establish the impossibility of such a gene are based on a fallacious understanding of both genetics as well as the sociological and medical realities.

As I stated earlier, the question or whether or not such genes exist is an empirical question. As such, the question can only be decided by a judicious application of scientific methodology. Philosophical and ideological objections are irrelevant to the question. Likewise, it must be cautioned that while science may be able to answer the empirical question, it is not capable of addressing the moral and theological questions that surround the issue of homosexuality. The absence of such a gene (or genes) can not logically be used to condemn homosexuality but neither can its existence be used to validate it. To do either would be to engage the Naturalistic Fallacy to the benefit of no one. We should be aware of the facts and realities of nature, of course, but what we do with those facts is a different question altogether.

Ratfish Redux

Behold, the ratfish!



This is a "living fossil" discovered by Brazilian scientists. It's related to sharks and rays.

The so-called Age of Discovery, when such organizations as the National Geographic Society were having to continual update the lists of new creatures, flora, and peoples, pretty much came to an end with the culmination of the epoch of European imperial expansion. New species are still discovered (mostly arthropods and the like), but the pace has slowed to a comparative trickle.

The oceans are the last great frontier on the planet that have remained largely unexplored. Such discoveries as this ugly little fish hold out the possibility that a new Age of Discovery may yet exist in our future.

Addendum

One of the challenges to writing on-line essays is finding good links for the essays. I try to avoid linking for the sake of linking instead stiving to make every link informative, illustrative and, if at all possible, entertaining. Sometimes this is easier than at other times. My recent essay on the subject of Sexual Dimorphism proved to be an especial challenge. There are a lot of great articles and studies out that pertain to the subject but most of what I'd like to have linked to is in the form of professional journals that either don't have an online presence or which require subscriptions to read the articles.

As it happens, I just stumbled across a site that would have made a perfect link (actually, several perfect links). Rather than going back and re-editing the essay, I've decided to simply post the link here. The site is hosted by the University of Plymouth Department and is meant as a supplement to their Psych 141 course (Biological Perspectives on Gender Differences).

I would particularly like to point out the section pertaining to the development of external genitalia (as well as the accompanying animation) and, even more pertinantly, the site's article on a boy who had suffered an accidental castration due to a botched circumcision who was subsequently raised as a girl. I would also note that Slate contains a follow up to this rather sad story.

Please note that this site contains clinical nudity. There's nothing prurient but it has been pointed out that there are companies that would object to their employees browsing these images. Proceed with caution.

Some Thoughts on Human Sexual Dimorphism

In biology, the term used to describe the differences between the sexes of a species is sexual dimorphism. Dimorphism is just a fancy word meaning that something has two shapes. Even though the term seems dry and technical, there's something poetic about the notion that the sexes are a single thing with two sides.

The degree of dimorphism between the sexes of a species can vary profoundly. If you were to look at a typical dog, for instance, you'd have to lift the animal up and have a good look at its plumbing. You certainly couldn't make the distinction based on size, of the tone of its bark or even by such behavioral gauges such as its aggressiveness. The differences between male and female angler fish, by contrast, is so profound that it's difficult to accept that they are members of the same species. The males are a fraction of the females size and, disturbingly, attach themselves to the females, like parasites, and actually fuse to the females' bodies, acting as little more than attached sperm repositories.

In the overall scheme of things, humans are more alike than different. The most "obvious" differences are actually superficial. Breasts, to cite the most visually distinctive difference, are essentially the same on both males and females. Male breasts can even be made to engorge and to lactate with the introduction or suppression of certain hormones. Even the genitals of men and women are, essentially, the same organ with male and female versions being little more than complex inversions of one another – a reproductive expert can draw a one to one mapping between every part of them.

One of the common misconceptions about what distinguishes men and women is whether a person has two X chromosomes or an X and Y chromosome. Strictly speaking, the chromosomal set you are born with offers nothing more than a strong genetic predilection towards one sex or the other. What actually determines your sexual development is your uterine environment. If you have a Y chromosome, there's a point in your development when the chromosome "activates" a particular cascade of sex linked hormones (most notably testosterone). It is this chemical environment that drives your sexual development beyond that point. It is entirely possible for this trigger to misfire. There are men who have two X chromosomes and there are women who have X and Y chromosomes. This is a fact that's caused quite a bit of controversy in the Olympics which, misguidedly, uses genetic standards to gauge sex in order to combat cheating.

Given that men and women are so physically close, it should not come as a surprise to find that we are cognitively close. It is, in fact, one of the great crimes of human history that, for millennia, women have been treated as being not only profoundly different from men but intellectually inferior to them. Given this sad history, it ought not be a surprise that once this view was challenged, there was a tendency to go too far in claiming that men and women are entirely identical in mind. Decades of research have shown that there are consistent differences between the way that men and women think but the differences aren't intellectual and they are subtle.

Men and women react to pain differently. Men and women bond with their offspring differently. Men and women deal with spatial and abstract problems differently. There are apparent differences in verbal memory, emotional memory, and how we perform acts of coordination (women do better). In listing the differences it is easy to get swept up in them to the point where we are tempted to declare that men and women are utterly unalike. The truth, however, is that even in the areas where we have differential levels of performance (e.g., performing spatial manipulations) there are broad overlaps.

One of the thorniest questions facing cognitive science (right up there with the genuine minefield of the question of racial differences) is whether or not there are any behavior differences and, if so, what is their source. It is easy to note that women and men exhibit different modes of socialization. In simplistic terms, men have a competitive social environment whereas women tend to focus of building complex interpersonal structures. There is, of course, the endless sort of anecdotal observations such as the that women tend to enjoy shopping more than men all the way down to the banal distinctions between guy flicks and chick flicks. For anyone but a dyed in the wool egalitarian, it's apparent that men and women do behave differently. The big question, however, is why.

Anyone who has spent any time watching the commercials that play during children's cartoon shows knows that there's a heavy amount of sexual segregation in the products that advertisers offer. Excepting only such neutral grounds as breakfast cereals and candies, certain products are pitched exclusively at boys while others are pitched exclusively at girls. Boys are sold miniature cars and trucks, weapon-like toys (nerf guns, spray guns, and the like), and all sorts of monsters and robots. Girl toys tend to focus on motherhood (lifelike baby and child dolls), romantic items (fashion accessories, jewelry, etc), and role playing (doll houses, adult dolls, pets, etc).

It is very tempting to say that boys and girls see themselves as having boy and girl roles because they experience heavy socialization. It may even be largely true, but we must be careful lest we confuse the causative associations. Do boys and girls behave as they do because they get certain cultural messages on how to behave, or do the cultural messages conform themselves to a set reality? Do boys want toy soldiers because that's what they're sold or do we sell boys toy soldiers because girls are, predispositionally, uninterested in them?

It's a damnably difficult question to answer. If it were possible to take children and raise them in a controlled laboratory environment with careful sets of controls, it would be relatively easy to glean some answers. Fortunately, we don't ethically condone that sort of experimentation. For better or worse, researchers are restricted to subjects that have invariably suffered all sorts of potential social contamination. It would be tempting to simply write the whole question off as insoluble. It would be irresponsible for us to do so, however. Even if the answers are not easy to determine, the question is important.

Thirty years of attempts to convince women that they should consider technical careers has done little to improve the presence of women in such fields as physics, mathematics, engineering, computer programming and most of the sciences as a whole. Given that these are precisely the careers that are driving modern technology and, hence, modern culture, this lack of representation is a source of legitimate concern. If there is something that can be done in order to fix this disparity then we, as a society, ought to do so. On the other hand, there are few things worse than misguided attempts at social engineering. It is important for us to know what the reality is and to adjust to it accordingly.

This task is complicated by the presence of all sorts of political agendas. On the one hand, you have proponents of so-called traditional values who think that it's an error to encourage any deviation from the past. On the other hand, you have groups who think that any efforts to so much probe the potential differences between the sexes must, automatically, be construed as acts of sexism and subjugation. Either side is motivated by concerns that it considers legitimate but I firmly believe that reality can not be bent to ideology and that any effort to do so is folly.

We are a dimorphic species. We are also, men and women, far more alike than different. To properly understand ourselves, we must illuminate those differences while, at the same time, resisting the urge to exaggerate them. If we can not manage this task, we can not understand ourselves. If we do not understand ourselves then we are charting our course by false stars.