Wednesday, March 26, 2008

Lizards Undergo Rapid Evolution after Introduction to a New Home

In 1971, biologists moved five adult pairs of Italian wall lizards from their home island of Pod Kopiste, in the South Adriatic Sea, to the neighboring island of Pod Mrcaru. Now, an international team of researchers has shown that introducing these small, green-backed lizards, Podarcis sicula, to a new environment caused them to undergo rapid and large-scale evolutionary changes.

"Striking differences in head size and shape, increased bite strength and the development of new structures in the lizard's digestive tracts were noted after only 36 years, which is an extremely short time scale," says Duncan Irschick, a professor of biology at the University of Massachusetts Amherst. "These physical changes have occurred side-by-side with dramatic changes in population density and social structure." Results of the study were published March 25 in Proceedings of the National Academy of Sciences.

Researchers returned to the islands twice a year for three years, in the spring and summer of 2004, 2005 and 2006. Captured lizards were transported to a field laboratory and measured for snout-vent length, head dimensions and body mass. Tail clips taken for DNA analysis confirmed that the Pod Mrcaru lizards were genetically identical to the source population on Pod Kopiste.

Observed changes in head morphology were caused by adaptation to a different food source. According to Irschick, lizards on the barren island of Pod Kopiste were well-suited to catching mobile prey, feasting mainly on insects. Life on Pod Mrcaru, where they had never lived before, offered them an abundant supply of plant foods, including the leaves and stems from native shrubs. Analysis of the stomach contents of lizards on Pod Mrcaru showed that their diet included up to two-thirds plants, depending on the season, a large increase over the population of Pod Kopiste.

"As a result, individuals on Pod Mrcaru have heads that are longer, wider and taller than those on Pod Kopiste, which translates into a big increase in bite force," says Irschick. "Because plants are tough and fibrous, high bite forces allow the lizards to crop smaller pieces from plants, which can help them break down the indigestible cell walls."

Examination of the lizard's digestive tracts revealed something even more surprising. Eating more plants caused the development of new structures called cecal valves, designed to slow the passage of food by creating fermentation chambers in the gut, where microbes can break down the difficult to digest portion of plants. Cecal valves, which were found in hatchlings, juveniles and adults on Pod Mrcaru, have never been reported for this species, including the source population on Pod Kopiste.

"These structures actually occur in less than 1 percent of all known species of scaled reptiles," says Irschick. "Our data shows that evolution of novel structures can occur on extremely short time scales. Cecal valve evolution probably went hand-in-hand with a novel association between the lizards on Pod Mrcaru and microorganisms called nematodes that break down cellulose, which were found in their hindguts."

Change in diet also affected the population density and social structure of the Pod Mrcaru population. Because plants provide a larger and more predictable food supply, there were more lizards in a given area on Pod Mrcaru. Food was obtained through browsing rather than the active pursuit of prey, and the lizards had given up defending territories.

"What is unique about this finding is that rapid evolution can affect not only the structure and function of a species, but also influence behavioral ecology and natural history," says Irschick.

Source: University of Massachusetts Amherst

Wednesday, March 19, 2008

The bioecological model

An email sent to Kristin Jacobson, Assistant Professor, University of Chicago Medical School

Dear Prof. Jacobson,

I was just leafing through my University of Chicago Magazine this evening when I came across the article summarizing your new grant. I have to say I was amazed. Though the author tiptoed around the area under investigation, you are entering some very choppy waters. The attempt to identify the genetic and biological contributions to anti social behavior and cognition is normally considered taboo, since it inevitably ventures into racial variables. Though I am familiar with some work reported in press releases and abstracts of journals, as you can see from my weblog, most researchers, considering the downside, tend to avoid such studies, even with the best of intentions.

I can't help be reminded of the unfortunate lesson of Chicago's Dr. Bruce Lahn, with whom you undoubtedly have discussed your research interests. As was noted several years ago in the Wall Street Journal: The university's patent office is also having second thoughts. Its director, Alan Thomas, says his office is dropping a patent application filed last year that would cover using Dr. Lahn's work as a DNA-based intelligence test. "We really don't want to end up on the front page...for doing eugenics," Mr. Thomas says. Lahn himself has backed away from the research that brought him so much notoreity and made Univeristy officials "nervous". As the Journal reported Lahn saying about the neurogenetics: "It's getting too controversial." Won't Dean Madera and Media Relations Director John Easton, or their successors, be equally concerned about what you might turn up? Lawrence Summers was hounded out of the presidency of Harvard for just injecting some off the cuff and off the record speculation about neurological gender differences that flow from the data.

I commend you for your courage, since I do believe with you that empirical evidence about the interplay of nature and nurture should inform our public policy decisions.


Tom Merle
M.A. '74

Teenagers behaving badly
Univerity of Chicago Magazine, Mar/April '08

They’re getting high off cold meds, posting lewd photos on MySpace, and developing online gambling addictions. The sins may be new, but problem behavior has long been a rite of passage for U.S. teens. In fact, says behavioral geneticist Kristen Jacobson, troublemaking is so common for Americans between ages 14 and 18 that “it’s almost normative.” Yet individual differences abound. Why do some youths make relatively harmless crank calls while others wield knives and bully classmates? Why do some emerge from adolescence as well-adjusted adults while others sink into a cycle of delinquent behavior? Jacobson, an assistant professor of psychiatry, wants to understand the divergence. With a $1.5 million National Institutes of Health New Innovator Award she won this past September, she’ll study how environmental and genetic influences interact to shape adolescent conduct, including nonviolent delinquency, aggression, and substance abuse.

When delinquency persists past adolescence, Jacobson says, genes may be partly to blame.
“People may be acting out for genetic reasons, but they may be acting out for environmental reasons as well,” says Jacobson. Known as the “bioecological model,” her chosen approach sees individual development as a set of interactions between genes and environmental factors such as family, school, and community. Much of Jacobson’s research on teens has focused on twin studies, and she is associate director of the psychiatry department’s twin-studies program. By comparing identical twins, who share all of their DNA, with fraternal twins, who share only half, geneticists can better pinpoint which behaviors may be genetically linked.

Jacobson describes many of the environmental influences she studies as “grandmother science,” or things a typical grandmother might warn her grandchild about. Peer pressure is one example. “Kids who hang out with other kids who do bad things tend to get in trouble,” she says. In fact, most problem behavior, both aggression and nonviolent delinquency, such as lying to parents and stealing, drops off as teens grow up and leave high school.

Yet some adolescents exhibit more lasting problems. In research conducted in 2003, Jacobson analyzed twin-studies data to identify two pathways of antisocial conduct: adolescent-limited and life-course persistent. Each is characterized by a different degree of heritability, or genetic influence. The first group, which makes up roughly 50–75 percent of troubled teens, describes those whose acting out, influenced mainly by environmental factors, tapers off after adolescence.

Children whose difficulties continue, on the other hand, make up less than ten percent of the population and exhibit higher genetic influence. They often act out earlier in life and score higher on early-childhood tests that measure maternal depression, maternal life stress, low socioeconomic status, single parenthood, home environment, and parental treatment.

As genetic technology improves and more human-development researchers seek out the individual genes that influence behavior, Jacobson continues to stress the importance of environmental variables, which may even alter how genes express themselves. A 2005 study in the Proceedings of the National Academy of Sciences, for example, found variation in identical twins’ DNA methylation levels, a driver of gene expression. Because both siblings have the same gene set, says Jacobson, whose NIH study builds on these findings, such a divergence may result from environmental influences—the level of maternal care in infancy is one example—that cause twins’ genes to express themselves differently.

If the way a parent treats a child can change the body’s biology, Jacobson reasons, so might other environmental influences. Recent functional magnetic resonance imaging (fMRI) studies, for example, link early-life family adversity with decreased activity in the amygdala, the part of the brain related to emotion regulation and believed to play a role in developing aggressive behavior.

Understanding how deviance develops on both genetic and environmental levels could offer new ideas on how to help at-risk teens. Researchers have long observed that children from low socioeconomic environments, a group over-represented by racial and ethnic minorities, show the worst developmental outcomes. Furthermore, the influence of genes on those outcomes may be different from other populations. As a graduate student at Pennsylvania State University, Jacobson coauthored a 1999 paper in Child Development finding that genetic influence on verbal IQ varied depending on parents’ education levels. For children from a highly educated family, genetic influence was greater than for those with less education. In other words, says Jacobson, environmental influences played a larger role on verbal IQ for the disadvantaged. [this does not follow]

Over the next five years her NIH study will investigate the environmental, psychosocial, biological, and genetic risk components of delinquency across socioeconomic and racial groups. The multidisciplinary project—one of the only large-scale genetic studies of adolescent delinquency to look at ethnicity and socioeconomic status beyond Caucasians—will use in-school surveys, interviews, computer-based tests of traits like impulsivity, and fMRI to parse the effects of nature and nurture....

Jacobson emphasizes that her project, an attempt to cull data at several levels, is more exploratory than hypothesis-driven. Thus while it would be premature for her to speculate on what intervention programs might best help at-risk teens, her work should shed light on why some kids struggle while others thrive. For teens whose bad behavior—not to mention whose parents and teachers—cries out for real-world solutions, Jacobson is laying critical groundwork.

Saturday, March 15, 2008

"...the biological pressures that whisper within men."

Do you Want a Man.... or a Worm?

Los Angeles Times
Among mammals, expecting monogamy tends to run against the grain of nature.
By David P. Barash
March 12, 2008
As an evolutionary biologist, I look at New York Gov. Eliot Spitzer's now-public sexual indiscretions and feel justified in saying, "I told you so."

One of the most startling discoveries of the last 15 years has been the extent of sexual infidelity (scientists call it "extra-pair copulations" or EPCs) among animals long thought to be monogamous. It's clear that social monogamy -- physical association and child rearing between a male and a female -- and sexual monogamy are very different things. The former is common; the latter is rare.

At one point in the movie "Heartburn," Nora Ephron's barely fictionalized account of her marriage to reporter Carl Bernstein, the heroine tearfully tells her father about her husband's infidelities, only to be advised, "You want monogamy? Marry a swan." Yet thanks to DNA evidence, we know now that even those famously loyal swans aren't sexually monogamous.

One species that is, and, significantly, perhaps the only one that could be reliably designated as such, is Diplozöon paradoxum, a parasitic worm that inhabits the intestines of fish. Among these animals, male and female pair up while adolescents; their bodies literally fuse together, whereupon they remain sexually faithful until death does not them part.

One of the most important insights of modern evolutionary biology has been an enhanced understanding of male-female differences, deriving especially from the production of sperm versus eggs. Because sperm are produced in vast numbers, with little if any required parental follow-through, males of most species are aggressive sexual adventurers, inclined to engage in sex with multiple partners when they can. Males who succeed in doing so leave more descendants.

A story is told in New Zealand about the early 19th century visit of an Episcopal bishop to an isolated Maori village. As everyone was about to retire after an evening of high-spirited feasting and dancing, the village headman -- wanting to show sincere hospitality to his honored guest -- called out, "A woman for the bishop." Seeing a scowl of disapproval on the prelate's face, the host roared even louder, "Two women for the bishop!"

On balance, the Maori headman had an acute understanding of men. He also reflected a powerful cross-cultural universal: Around the world, high-ranking men have long enjoyed sexual access to comparatively large numbers of women, typically young and attractive. Moreover, women have by and large found such men appealing beyond what may be predicted from their immediate physical traits. "Power," wrote Henry Kissinger, "is the ultimate aphrodisiac."

Power-as-pheromone is pretty much the default among mammals. Elk, elephant seal, baboon or chimpanzee, in a wide array of species, females eagerly mate with dominant males while disdaining subordinates. And they do so, more or less, in harems.

Not surprisingly, before the homogenization of cultures that resulted from Western colonialism, more than 85% of human societies unabashedly favored polygamy. In such societies, men who accumulate power, wealth and status gain additional wives and consorts. In avowedly monogamous cultures, successful males accumulate a wife and often additional girlfriends. Even if, thanks to birth control technology, they do not actually reproduce as a result (and thus enhance their evolutionary "fitness"), they are responding to the biological pressures that whisper within men.

Part of being successful, moreover, is a tendency to feel entitled and often to be uninhibited -- in part because one outcome of our species-wide polygamous history is that successful men have been those who took risks, which paid off. The losers were mostly found among the unsuccessful bachelors who, by definition, did not contribute very much to succeeding generations of men, or to their inclinations.

All of which contributes to the apparent sex appeal of such less-than-stunning physical specimens as Kissinger, Woody Allen and Bill Clinton, not to mention the persistence of sex scandals among the popular and powerful across the political and ideological spectrum, including Thomas Jefferson, JFK, Hugh Grant, Newt Gingrich, Larry Craig and a long list, receding almost to the infinite past as well as likely into the indefinite future. For men at the top -- rock stars, successful athletes, politicians, wealthy CEOs, the jet-set glitterati -- such opportunities are exceedingly numerous, not so much because they have insatiable sex drives but because they are dominant males in a biologically randy species.

Some readers may bridle at this characterization of Homo sapiens as EPC-inclined, but the evidence is overwhelming. That doesn't justify adultery, by either sex, especially because human beings -- even those burdened by a Y chromosome and suffering from testosterone poisoning -- are presumed capable of exercising control over their impulses. Especially if, via wedding vows, they have promised to do so. After all, "doing what comes naturally" is what nonhuman animals do. People, most of us like to think, have the unique capacity to act contrary to their biologically given inclinations. Maybe, in fact, it is what makes us human.

But even a smidgen of evolutionary insight suggests that maleness plus money plus political power isn't likely to add up to the kind of sexual restraint that the public expects. A concluding word, therefore, to the outraged voters of New York state: You want monogamy? Elect a swan. Or better yet, a Diplozöon paradoxum.

David P. Barash, an evolutionary biologist, is professor of psychology at the University of Washington.

Impulsive Aggressive Behavior

Nature or nurture - why do some of us see red?

University of Manchester researchers are investigating why some people remain calm in the face of life's niggles, while others 'flip' with little provocation.

Recent studies using new brain-imaging technology have discovered that a change in the brain's neurochemical activity may be related to increased impulsive aggression (when someone unexpectedly reacts violently with little provocation, as opposed to someone deliberately 'looking for trouble'). Now psychologist Angela Rylands wants to deploy the University's world-leading HRRT PET brain scanner, based at its Wolfson Molecular Imaging Centre (WMIC), as part of a project to find out more.

Angela said: "Positron emission tomography (PET) scanning has revealed that a deficit in brain serotonin neurotransmission may leave some people more prone to aggression and impulse control disorders. I want to establish to what extent such behaviours are rooted at a molecular level and how much does learning from the environment around us also play a part."

One of her case studies, 39-year-old former professional bodyguard turned retail manager Carl Hayes, is available for interview. Carl is taking part in order to find out why he loses his temper so easily (he once set light to £800 in a row with his ex-wife).

Angela is looking for other males aged 18 or over, who do not use illegal drugs, and who feel they may be impulsively aggressive to have their brains scanned, to develop the team's understanding of the processes at work. Genetic samples will also be taken to enable them to investigate any interesting polymorphisms (genetic markers which occur in different forms from person to person), as previous research has implicated specific polymorphisms in aggressive behaviour.

Angela will then carry out psychological assessments of participants' previous exposure to aggression and neuropsychological tests to assess their aggressive capacity.

"It's well known that the prefrontal brain regions are associated with normal social and emotional behaviour, and that people with damage to these areas are more impulsive and aggressive," Angela continued. "We now want to see whether subtle deficits in the brain's serotonin system can explain differing levels of aggression in people who don't have brain damage. Our first theory is that higher capacity for impulsive aggression will be found in those with the lowest levels of brain serotonin. The second is that a combination of our genetic makeup and a harsh or abusive childhood may lead to the brain serotonin system not developing normally.

"The areas of serotonin neurotransmission that we are interested in are in the brain regions associated with inhibitory control. Of course people need to take responsibility for their own behaviour, but it could be that some people have difficulties controlling aggression because of impaired regulation of negative emotions or social behaviour by the serotonin system in their brains.

"The genetic samples we take and our assessments of people's exposure to aggression in their childhoods may uncover the factors that adversely influence the developing serotonin system and lead to a dysfunctional system in the mature adult.

"If we can get to the root of impulsive aggressive behaviour - be it nature, nurture or a combination of the two - it could help us to identify how we can break the cycle of impulsive and aggressive behaviour and intervene with future generations at risk from losing control."

She added: "This work may prevent future generations suffering the consequences of impulsive aggression.

"Aggression that occurs as a consequence of poor impulse control presents a burden for society. Each year over half a million people worldwide die from interpersonal violence. The financial burden of violent crime adds to this, incurring expenditures for the criminal justice system, for the incarceration of offenders and to local victims. Socioeconomic costs and public health issues persist, as a consequence of aggressive behaviour.

"The underpinnings of aggression should be identified to enable advancement towards preventative measures."

Participants will visit the WMIC for a screening session, followed by a scan if appropriate. They will then undergo psychological assessments of their previous exposure to aggression, and neuropsychological tests to assess their aggressive capacity. Volunteers will be reimbursed for their time and travel expenses.

Source: University of Manchester

Sunday, March 09, 2008

Hormones, Genes and the Corner Office

The New York Times

March 9, 2008



Men, Women, and the Real Gender Gap.

By Susan Pinker.

340 pp. Scribner. $26.

Why do girls on average lead boys for all their years in the classroom, only to fall behind in the workplace? Do girls grow up and lose their edge, while boys mature and gain theirs?

Ten years ago, no one would have thought to ask. The assumption that boys dominated at school as well as at work, while girls were silenced or ignored, seemed beyond dispute. But in her new book, “The Sexual Paradox,” a ringing salvo in the sex-difference wars, Susan Pinker stacks up the evidence of boys’ classroom woes and girls’ triumphs. “In the United States, boys are three times as likely to be placed in special education classes, twice as likely to repeat a grade and a third more likely to drop out of high school,” she writes. Tests of 15-year-olds in 30 European countries show girls far outstripping boys in reading and writing and holding their own in math. Boys are overrepresented in the top 1 percent of math achievers, but there are also more of them at the bottom. A 2006 economics study showed universities practicing affirmative action for men so that superior female applicants wouldn’t swamp them. “If you were to predict the future on the basis of school achievement alone,” Pinker writes, “the world would be a matriarchy.”

And yet, of course, it is not. Once they move from school to work, men on average earn more money and run more shows. They particularly dominate in national government, the corporate boardroom and the science laboratory. Meanwhile, women are more likely to leave the labor force and to end up with lower pay and less authority if they come back.

Pinker, a psychologist and a columnist at The Globe and Mail in Canada, is careful to remind her readers that statistics say nothing about the choices women and men make individually. Nor does she entirely discount the effect of sex discrimination or culture in shaping women’s choices. But she thinks these forces play only a bit part. To support this, Pinker quotes a female Ivy League law professor: “I am very skeptical of the notion that society discourages talented women from becoming scientists,” the professor writes. “My experience, at least from the educational phase of my life, is that the very opposite is true.” If women aren’t racing to the upper echelons of science, government and the corporate world despite decades of efforts to woo them, Pinker argues, then it must be because they are wired to resist the demands at the top of those fields.

Thus, Pinker parks herself firmly among “difference” feminists. Women’s brains aren’t inferior, she argues, but they vary considerably from men’s, and this is the primary explanation for the workplace gender divide. Women care more about intrinsic rewards, they have broader interests, they are more service-oriented and they are better at gauging the effect they have on others. They are “wired for empathy.” These aren’t learned traits; they’re the result of genes and hormones. Beginning in utero, men are generally exposed to higher levels of testosterone, driving them to be more competitive, assertive, vengeful and daring. Women, meanwhile, get a regular dose of oxytocin, which helps them read people’s emotions, “the truest social enabler.” Then there’s prolactin, which, along with oxytocin, surges during pregnancy, breast-feeding and caretaking. Together, the hormones produce such a high that mother rats choose their newborns over cocaine.

Many of the scientific claims are familiar from previous books that pump up findings on sex difference, like “The Female Brain,” by the neurologist Louann Brizendine. Pinker goes even further by drawing a straight line from those blissed-out rats to human mothers who dial back at work. Because of their biological makeup, she argues, most women want to limit the amount of time they spend at work and to find “inherent meaning” there, as opposed to domination. “Both conflict with making lots of money and rising through the ranks,” she points out.

Pinker is surely right to contest what she calls the “vanilla male model” of success — “that women should want what men want and be heartily encouraged to choose it 50 percent of the time.” Or that when employers say jump, employees should always say how high. Even as they work fewer hours for less status and less money, on average, more women report that they are satisfied with their careers. Maybe men might well think the same if more of them felt they could cut back. But Pinker’s difference feminism doesn’t really allow for that possibility. She is a believer: “The puzzle is why the idea of sex differences continues to be so controversial,” she writes.

In her zeal, Pinker veers to the onesided. She doesn’t acknowledge that some of the research cited in her footnotes is either highly questionable as social science (Louise Story’s 2005 article in The New York Times, for instance, about her survey of Ivy League women’s aspirations) or has never been replicated — like the findings from Simon Baron-Cohen’s laboratory that newborn girls showed more interest in looking at human faces, while newborn boys preferred mechanical mobiles. Pinker omits the work of scientists who have shown that sex-based brain differences pale in comparison to similarities. We shouldn’t wish the role of sex differences away because they’re at odds with feminist dogma. But that doesn’t mean we should settle for the reductionist version of the relevant science, even if the complexity doesn’t make for as neat a package between hard covers.

Pinker also doesn’t acknowledge that some scientists wouldn’t accept the premise behind her chapters about male fragility. She cites men with Asperger’s syndrome and attention deficit disorder as examples of what she calls the “extreme male brain.” These men are train wrecks in school but then get on track in adulthood, when they can focus singlemindedly on their chosen fields. Pinker argues that their experience helps explain the general male lag at school and jump ahead at work. It’s true that men are more likely than women to suffer from Asperger’s and from some forms of A.D.D. But do their particular outsize talents and deficits really shed light on the workings of the average man’s brain? That question is hardly settled, and Pinker seems a bit glib when she fails to say as much.

Pinker also skips past an answer to the book’s central question that may have more explanatory power than her other arguments, even if it’s more prosaic and familiar to many a parent. Boys lag dramatically behind girls in terms of psychological development and physical resilience and then start to catch up as teenagers, as a long-running and wellknown study Pinker cites documented. Maybe after a few years as girls’ developmental equals, boys are ready to compete in the work force — and then zoom ahead as cultural norms and discrimination push women back. After all, why would girls’ hard-wired predilection against competition stay on ice while they blithely sweep all the academic honors and then kick in only at work?

Despite such unanswered questions, Pinker deserves credit for hacking away at the vanilla male model. She is right to point out that “grueling hours do not always translate into productivity” and to seethe at employers for ratcheting up their demands “even while extolling the virtues of gender balance.” And she is also right to call on schools to give the troubles of boys a fair share of attention. Pinker may not convey all the complexity that goes into making many men’s and women’s lives different, but she has a good prescription for helping more of us be our best selves.

Emily Bazelon is a senior editor at Slate.