Category: Research Blogging

Is corn the new milk? Evolutionarily speaking, that is.

Is corn the new milk? Evolutionarily speaking, that is.

 

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colorful fall corn Corn. Photo by srqpix.

ResearchBlogging.orgIt is a widespread misconception that, as we developed the technology to reshape our environment to our preferences, human beings neutralized the power of natural selection. Quite the opposite is true: some of the best-known examples of recent evolutionary change in humans are attributable to technology. People who colonized high-altitude environments were selected for tolerance of low-oxygen conditions in the high Himalayas and Andes; populations that have historically raised cattle for milk evolved the ability to digest milk sugars as adults.

A recent study of population genetics in Native American groups suggests that another example is ripening in the experimental fields just a few blocks away from my office at the University of Minnesota: Corn, or maize, may have exerted natural selection on the human populations that first cultivated it.

The target of this new study is an allele called 230Cys, a variant of a gene involved in transporting cholesterol. 230Cys is known only in Native American populations, and it’s associated with abnormally low production of HDL cholesterol (that’s the “good” kind of cholesterol) and thereby increased risk for obesity, diabetes, and heart disease. In Native American populations, the genetic code near 230Cys shows the reduced diversity associated with a selective sweep, which suggests that, although it’s not particuarly helpful now, this variant may have been favored by selection in the past.

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One way to successfully invade a habitat: eat the competition

One way to successfully invade a habitat: eat the competition

 

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Harmonia axyridis, adulte The Harlequin ladybug, Harmonia axyridis. Photo by Ombrosoparacloucycle.

ResearchBlogging.orgThe Asian Harlequin ladybug, Harmonia axyridis, eats aphids like they’re Popplers, and it’s been repeatedly introduced into the U.S. and Europe to do exactly that. But since it was first introduced, H. axyridis has spread of its own accord, and displaced native ladybugs. This isn’t just because the Harlequin ladybug eats more aphids, or breeds faster, than the locals; it looks like part of the Harlequin’s success is due to the fact that it eats its native competition.

Although they’re known for eating aphids, most ladybugs are perfectly willing to engage in intraguild predation—that is, to eat other insects that are themselves primarily predators. Including other ladybugs. So a team at Wageningen University in the Netherlands set out to see whether H. axyridis might engage in a different kind of intraguild predation than its native competitors—do the Harlequins preferentially attack ladybugs of different species, and, when they do, are they more likely to win?

The team tested this in what they call a “semi-field” experiment, by creating encounters between ladybug larvae on individual leaves of small potted lime trees. They chose two other ladybug species, Coccinella septempunctata and Adalia bipunctata, for comparison to, and competition with, H. axyridis. Then, on the leaves of small potted lime trees, the researchers set up larval ladybug death matches.

Death matches for science, mind you.

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Is female orgasm adaptive? Let’s ask the clitoris.

Is female orgasm adaptive? Let’s ask the clitoris.

ResearchBlogging.orgWhether or not a trait is an adaptation, shaped by natural selection for a specific function, can be a surprisingly contentious question in evolutionary biology. When the trait in question belongs to human beings, though, “contentious” reaches a whole new level—because when evolutionary biologists consider humans, their conclusions get personal.
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Erotic sculpture on temple wall, Khajuraho, India. Photo by Abhishek Singh aka Bailoo.

Among the myriad traits and behaviors of Homo sapiens evolutionary biologists might choose to study, few can be as personal as the female orgasm. The adaptive function of male orgasm is about as clear-cut as possible—it’s a mechanistic necessity for uniting a sperm with an egg. But while female orgasm is enjoyable (or so I am told; this is as lousy a point as any to admit that my expertise in this phenomenon is purely academic), it isn’t necessary for fertilization. No man can be a father without having had at least one orgasm, but a woman could conceivably give birth to a huge family without having any.

To explain the existence of female orgasm in an evolutionary context, then, biologists have two options: (1) discover a way in which female orgasm shapes reproductive success indirectly, or (2) conclude that female orgasm isn’t an adaptation. Possibilities advanced for the first option range from the benefits of closer bonding with a mate—sex is, after all, about more than mere reproduction—to suppositions that the contractions associated with orgasm help draw semen into a woman’s reproductive tract.

The argument in support of non-adaptive female orgasm takes a developmental perspective: that female orgasm is really male orgasm, as experienced in a female developmental context. That is, women have orgasms for the same reason men have nipples—because the anatomies of both sexes are constrained by their origins in the same underlying developmental program. If this is the case, natural selection would work to optimize male orgasm, without necessarily affecting female orgasm—and that suggests a way to test whether female orgasm is an adaptation.

Natural selection removes less-fit versions of traits from a population—making that trait less variable within the population under selection. Traits that don’t affect survival or reproductive success, on the other hand, are free to accumulate variation via mutation. So non-adaptive traits can be identified by comparing their variation to traits with known adaptive functions.

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Who cares what natural selection thinks, anyway? Photo by JorgeMiente.es.

Psychologist Kim Wallen and philosopher of science Elisabeth Lloyd (who had advanced the hypothesis that female orgasm is non-adaptive in a 2005 book) made just such a comparison in a 2008 study. Variation in female orgasm would be challenging to measure, so they used the clitoris as an anatomic proxy. This let them use the penis—which shares a developmental origin with the clitoris and is presumably under natural selection associated with male sexual function—as an adaptive standard for comparison. In comparison to (flaccid) penis length, Wallen and Lloyd found that clitoris length was indeed more variable [$a]. As a second control, the authors also compared variation in clitoris and penis length to variation in the length of women’s vaginas, understanding that this trait, unlike the clitoris, is important for female reproductive success. Vaginal length turned out to be about as variable as penis length, and much less so than clitoris length.

There are several objections to be made to Wallen and Lloyd’s analysis, and many were made in a response [$a] by evolutionary biologist Vincent Lynch. Lynch objected to the use of length as the focal measure for the size of the clitoris, and showed that clitoral volume was about as variable as penile volume. (I would add that the study of social insects Wallen and Lloyd cite as a precedent for their analysis isn’t actually focused on variation, but on the symmetry of traits under consideration, which is not quite the same thing.) More critically, though, Lynch points out that there isn’t any known relationship between clitoral size and ability to achieve orgasm—so the data don’t have the bearing on the question that Wallen and Lloyd assigned in the first place. Lynch concluded that female orgasm is an adaptation after all—a more conservative interpretation of his result is that we can’t answer the question by measuring clitorises.

Understanding the evolution of human sexual behaviors can help us to figure out how best to navigate the tricky business of a sexual relationship with another person—an approach most recently exemplified in the book Sex at Dawn. But we also tend to view evidence that natural selection favors a particular trait or behavior as a kind of approval, or as evidence of what is “natural.” That’s silly. Whether or not they help to make more babies, orgasms are fun, and they’re a wonderful part of our most intimate expression of affection and love. In some respects, that’s all we need to know.

References

Crespi, B., & Vanderkist, B. (1997). Fluctuating asymmetry in vestigial and functional traits of a haplodiploid insect. Heredity, 79 (6), 624-30 DOI: 10.1038/hdy.1997.208

Lynch, V. (2008). Clitoral and penile size variability are not significantly different: lack of evidence for the byproduct theory of the female orgasm. Evolution & Development, 10 (4), 396-7 DOI: 10.1111/j.1525-142X.2008.00248.x

Wallen K, & Lloyd EA (2008). Clitoral variability compared with penile variability supports nonadaptation of female orgasm. Evolution & development, 10 (1), 1-2 DOI: 10.1111/j.1525-142X.2007.00207.x


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J.B.S. Haldane and the case of the revivified head

J.B.S. Haldane and the case of the revivified head

ResearchBlogging.orgHere’s a nicely gruesome image for the week of All Hallows’ Eve.

“I dreamed I was in a dark room,” said Jane, “with queer smells in it and a sort of low humming noise. Then the light came on … I thought I saw a face floating in front of me. … What it really was, was a head (the rest of a head) which had had the top part of the skull taken off and then … as if something inside had boiled over. … Even in my fright I remember thinking, ‘Oh, kill it, kill it. Put it out of its pain.’ … It was green looking and the mouth was wide open and quite dry. … And soon I saw that it wasn’t exactly floating. It was fixed up on some kind of bracket, or shelf, or pedestal—I don’t know quite what, and there were things hanging from it. From the neck, I mean. Yes, it had a neck and a sort of collar thing round it, but nothing below the collar; no shoulders or body. Only these hanging things. … Little rubber tubes and bulbs and little metal things too.”
—Jane describes the disembodied Head in That Hideous Strength

Before he started The Chronicles of Narnia, C.S. Lewis tried his hand at science fiction. Lewis’s Space TrilogyOut of the Silent Planet, Perelandra, and That Hideous Strength—is like H.G. Wells dunked in (by modern American standards) gentle British Christianity. As in Narnia, Lewis wrote the Space Trilogy with a thesis in mind. The villains of Lewis’s imagined universe are materialistic scientists. In the first two books, the protagonist fights the scientists to preserve prelapsarian conditions among the intelligent inhabitants of Mars and Venus, respectively. The third book returns to Earth, where the evil scientists are plotting to take over the planet in the service of a demon-possessed disembodied head kept alive by technology that would’ve put Frankenstein off his lunch.

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J.B.S. Haldane. Photo via limjunying.

Lewis derived the scientists’ ideology, and one of the evil scientist characters in particular, from the writings and person of the evolutionary geneticist J.B.S. Haldane—which is not surprising, since Haldane was something of the Richard Dawkins of his day, a visible public advocate for the scientific worldview. What is surprising, though, is that Lewis may have had a perfectly good reason to connect Haldane to an artificially resurrected head: five years before the publication of That Hideous Strength, Haldane had narrated a film depicting just such an experiment.

The film, “Experiments in the Revival of Organisms,” depicts a series of blood transfusion procedures developed by a Soviet medical researcher, including the (apparent) revival of a dog’s severed head. It’s a fascinating cultural artifact in its own right, but it’s even more interesting as an element in Haldane’s personal history of mixing his scientific work with politics.

Geneticist, physiologist, human guinea pig

John Burdon Sanderson Haldane was one of three early Twentieth Century biologists (the others being R. A. Fisher and Sewall Wright) who knit together Charles Darwin’s theory of evolution by natural selection with Gregor Mendel’s discovery of discrete genetics. Haldane’s key contributions include a series of journal articles, “A mathematical theory of natural and artificial selection,” published between 1924 and 1934. The first entry, a mathematical model of natural selection [PDF], uses notation that looks somewhat odd today but otherwise builds the very logic I learned in my population genetics course.

Haldane’s population genetics work treats biological systems like physical or chemical ones—for instance, aiming to deduce the strength of natural selection acting on a population from records of evolutionary change over time or space. In the paper I linked to above, Haldane used his model of natural selection to estimate the strength of selection acting on peppered moths, which famously evolved darker coloration after the industrialization of England. In another, he proposed that the width of a clinal transition from one form of a species to another can indicate the strength of selection favoring each form at either end of the cline [PDF].

This tendency to treat biology like chemistry or physics reflected his scientific background. His father, John Scott Haldane, was renowned for research in respiratory physiology, and included J.B.S. in his scientific work from a very young age. J.B.S. Haldane’s first teaching position, at Oxford, was in physiology—and this was the focus of most of his early research. During the first World War, the Haldanes collaborated to test gas masks for the Allies, a project in which J.B.S. used himself as a test subject. J.B.S. conducted much of his postwar physiological research on himself, declaring that trained physiologists made the best test subjects, because they could accurately report their experiences during an experiment.

The scientist gets political

J.B.S. also developed a career as a public advocate for science and for a materialistic worldview, which helped attract criticism from social conservatives like C.S. Lewis—criticism Haldane returned with gusto. Haldane took the position that scientists doing potentially world-changing work had a duty to explain it to the public:

Many scientific workers believe that they should confine their publications to learned journals. I think, however, that the public has a right to know what is going on inside the laboratories, for some of which it pays. And it seems to me vitally important that the scientific point of view should be applied, so far as is possible, to politics and religion.
—quoted in Clark (1968), page 92.

One enduring example of Haldane’s work in this vein is an essay titled “Daedalus, or Science and the Future,” which extrapolated more than a century of advances in technology, and resulting changes in human society, from the state of science in 1923. Among the predictions Haldane made in “Daedalus” are the depletion of fossil fuels and the development of a hydrogen-based energy economy, and what he called “ectogenic” reproduction—human infants conceived and brought to term by entirely artificial means. Haldane did not uniformly endorse what he predicted, and particularly expressed reservations about artificial gestation; but he did stress that such technological change was probably inevitable. Aldous Huxley, a friend of Haldane’s from their undergraduate days at Oxford, would later make the idea of ectogenesis central to his dystopian novel Brave New World.

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Haldane addresses a political rally. Photo via Donald Fordyke.

Although he came from an aristocratic family—his uncle was the First Viscount Haldane—Haldane grew up with strong egalitarian and anti-authoritarian inclinations that became firmly entrenched during the war. He did not fail to notice that military chaplains took the safest possible postings, and he watched military brass accept honors for the gas mask testing project while the lower-ranked officers and civilians who risked their lungs doing the testing went unrecognized.

In the years leading up to World War II, Haldane’s anti-establishment leanings and his concern about the rise of fascism—which he saw firsthand in the Spanish Civil War, consulting for the Spanish Republican government on preparedness against air raids and gas attacks—led him toward the Communist Party, then one of the most visible opponents of fascism. In 1937, he accepted the position of science correspondent at the Daily Worker, a newspaper run by the Communist Party of Great Britain, for which he wrote hundreds of articles. When the Communist Party took up the issue of air raid preparedness in Great Britain, Haldane lent his expertise to the cause. He was, in short, a committed supporter.

“Experiments in the Revival of Organisms”

This is the context for Haldane’s role in the 1940 film “Experiments in the Revival of Organisms.” The film presents demonstrations of the work of Sergey Bryukhonenko, a Soviet scientist who developed a pumping system for blood transfusion called an “autojektor.” Other than the film itself, resources directly connecting the work to Haldane are remarkably thin—I find no mention of the film, or a professional connection between Haldane and Bryukhonenko, in the Haldane biography cited above, which is otherwise pretty painstaking about delineating Haldane’s Communist involvements.

Here’s the video, via the Internet Archive. Be warned—do not watch this if experimentation on animals makes you uncomfortable.

Haldane introduces the film onscreen, in his capacity as a “Fellow of the Royal Society” (F.R.S.), and testifies that “I have seen some of the experiments shown in this film actually carried out at the all-Russian Physiological Congress.” He then narrates (from off screen) a series of demonstrations of the autojektor apparatus, first in keeping an isolated heart beating; then in pumping blood through a pair of lungs on a dissecting tray—the blood enters the lungs unoxygenated, Haldane says, and leaves infused with oxygen.

Then comes the severed head. An animated sequence first explains the demonstration—that a severed head can be kept alive and responsive if connected to a blood supply via the autojektor. Then the film cuts to footage of a dog’s head (apparently) severed and resting on a dissecting tray, with an autojektor apparatus connected. The head responds to touch and noises, and even licks its lips when citric acid is daubed on them. The film concludes with what its makers evidently considered the most impressive demonstration, in which a dog is brought to clinical death by controlled blood loss, then revived by a transfusion using the autojektor.

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Haldane at his desk. Photo via notofthisreality.

The scientific and political crux of the film is that severed head. Even apart from the creepiness of the image, it’s suspicious—in its responses to stimulus, the head moves in ways that suggest it’s still attached to a neck. The camera is positioned in such a way that it wouldn’t be hard to hide a whole dog out of sight underneath the table on which the tray rests. If that portion of “Experiments” was faked to impress foreign audiences with Soviet medical technology that didn’t exist, was Haldane complicit in a scientific fraud?

It’s hard to say. It is clear that Haldane was an aggressively political man, but deliberate scientific fraud is not consistent with his character—it was a scientific question that finally caused him to dissociate from Soviet Communism, as we’ll see below. I think it more likely that Haldane was misled by a trusted colleague, in the context of supporting their shared political cause. Bryukhonenko’s work really did lay the groundwork for modern blood transfusion methods [$a], so it seems reasonable to think that Haldane had seen demonstrations of “some of the experiments shown in this film” firsthand, and then perhaps accepted as true a fraudulent report of the severed head experiment. Even if he was misled, “Experiments” represents an embarrassing lapse of judgment.

Putting the political cart before the scientific horse

Haldane ultimately ended his support for Soviet Communism over conflict with the other major area of his expertise, evolutionary genetics. Since before Haldane became a Communist, the Soviet regime under Josef Stalin favored a non- Mendelian theory of evolution developed by the agronomist Trofim Lysenko, who claimed that crop yields could be boosted through inheritance of acquired characteristics. This was mostly bunk, but it meshed well with Stalin’s political ideology, and as Lysenko gained political clout, he used it to run Mendelian geneticists out of the Soviet biological establishment.

The situation was the reverse of Haldane’s idealized relationship between science and public policy: politicians were demanding the results they wanted from scientists, not asking for guidance. In any event, it was hard for Haldane, one of the leading lights of population genetics, to avoid the conflict between his work and Lysenko’s. In 1940, the same year that “Experiments” was released, Haldane wrote a response to an article by Lysenko in the publication Science and Society that amounted to polite objection. It wasn’t until 1949, in an article for Modern Quarterly, “In defense of genetics,” (which I cannot, alas, find online) that Haldane refuted Lysenkoism in no uncertain terms. Shortly thereafter, in 1950, he stopped writing for the Daily Worker when it became clear that its editors favored political conclusions over scientific results.

Haldane remained inclined toward Marxism, but his differences with its political manifestation in the Soviet Union proved irreconcilable. He seems to have admitted, however tacitly, that those differences were an intellectual embarrassment for him. In his 1946 response to C.S. Lewis’s Space Trilogy, Haldane took a swipe at the Christian apologist that catches scientists, and J.B.S. himself, on the backswing:

Nevertheless, if Mr. Lewis investigates the facts honestly, he will probably discover … scientists are less likely than any other group to sell their souls to the devil. A few of us sell our souls to capitalists and politicians, and Mr. Lewis may have met some such vendors at Oxford. But on the whole we possess moral and intellectual standards, and live up to them as often as other people.

Special thanks are due to Luke Harmon, who sent me the link to “Experiments” when I was preparing to present about Haldane in his (Luke’s) “Giants of Evolution” seminar earlier this semester. That e-mail may be the single most awesome message I’ve ever received from a tenure-track professor.

References

Clark, R.W. (1968). JBS: The Life and Work of J.B.S. Haldane. New York: Coward-McCann. Google Books.

Haldane, J.B.S. (1923). “Daedalus, or, Science and the Future.” Kegan Paul, Trench, Trubner. HTML transcription via the University of Michigan.

Haldane, J.B.S. (1924). A mathematical theory of natural and artificial selection, part I. Trans. Cambridge Phil. Soc., 23, 19-31

Haldane, J.B.S. (1940). “Lysenko and genetics.” Science and Society, 4(4). HTML transcription via marxists.org.

Haldane, J.B.S. (1946). “Auld Hornie, F.R.S.” The Modern Quarterly, Autumn 1946. HTML transcription via marxists.org.

Haldane, J.B.S. (1948). The theory of a cline. Journal of Genetics, 48 (3), 277-84 DOI: 10.1007/BF02986626

Lewis, C.S. (1945). That Hideous Strength. Google Books.

Mussivand, T. (1999). Mechanical circulatory devices for the treatment of heart failure. Journal of Cardiac Surgery, 14 (3), 218-28 DOI: 10.1111/j.1540-8191.1999.tb00983.x


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