Wednesday, April 09, 2008

Genes, bad parenting keys to violence

From correspondents in London
April 10, 2008 04:00am

WHETHER a criminal teenager turns into a violent adult or grows out of crime, may be related to how low his ears are set or the types of food he was given as a child.

International research shows antisocial behaviour in young adults can be written into their genetic code, and made worse by bad parenting.

Indicators that an antisocial child may turn into a life-long violent criminal can be picked up in kindergarten, according to research summarised in this week's New Scientist magazine.

Of the 535 males and 502 females born in New Zealand in 1972 and 1973 who were signed up at birth to the University of Dunedin's Multidisciplinary Health and Development Study, those who dabbled in crime as a teenager can be divided into two clear groups, Terrie Moffitt from the Institute of Psychiatry in London said.

The more common type took up petty crime in adolescence keen to impress "badass" friends, she said.

But the more problematic type had biological predispositions to behaviour problems, the signs of which could be picked up as young as three years of age.

These children - more often boys - tended to have a low IQ, poor language skills, and were often diagnosed with attention-deficit hyperactivity disorder.

Minor physical anomalies such as low-seated ears or furrowed tongues - possibly a sign of poor neural development or damage - could also be signs.

Combined with bad parenting, poverty or abuse, these children were at greater risk of turning to a life-long criminal career, she said.

The early onset group accounted for only 10 per cent of the Dunedin males, but by the age of 26 they had accrued almost half of the violent convictions for the entire study.

Ms Moffitt's study of the Dunedin children also focused on the activity of an enzyme linked to aggression in both animals and humans.

By itself, the activity of the enzyme had little influence, but if the boys were more predisposed to aggression and had suffered some abuse as children they were three times as likely to be diagnosed with conduct disorder in adolescence and 10 times as likely to have been convicted of a violent crime in adulthood.

A US study has found there is a worrying subset of kids within the early onset group who do not react emotionally at all, scoring high in tests used for diagnosing adult psychopathy.

A study at the University of New Orleans found the 30 per cent of early onset antisocial children who showed these traits were most likely to turn to life-long violence.

Children in this group lack empathy and guilt, are thrill-seeking, fearless and narcissistic, says psychopathy expert James Blair from the National Institute of Mental Health in the United States.

Learning to fear punishment or recognise someone else's fear or sadness is difficult for psychopaths, he said.

"If they want something and punching someone in the face is the way to extract it, they might be more likely to engage in that kind of behaviour," he said.

Mr Blair said there are few signs that these psychopathic traits are caused by external factors like poor parenting or abuse, but they could be triggered by social forces like poverty.

The generally accepted approach to tackling the problem of antisocial and violent children is to intervene as young as possible with improved parenting.

Some experts say better parenting could even begin before birth.

A trial of monthly nurse visits throughout pregnancy and until the child's second birthday, in New York in the late 1970s, has been praised by scientists at the University of Colorado.

By the age of 15, the 315 children involved in the trial had only half of the number of arrests, one fifth the number of convictions, smoked and drank less and were less promiscuous than their untreated contemporaries.


Negligent, attentive mouse mothers show biological differences

Photo: Jeff Miller

In mice, child neglect is a product of both nature and nurture, according to a new study. Writing in the journal PLoS ONE on April 9, researchers from the University of Wisconsin-Madison describe a strain of mice that exhibit unusually high rates of maternal neglect, with approximately one out of every five females failing to care for her offspring.

By comparing the good mothers to their less attentive relatives, the group has found that negligent parenting seems to have both genetic and non-genetic influences, and may be linked to dysregulation of the brain signaling chemical dopamine.

As a possible model for human child neglect, these mice offer a valuable opportunity to investigate the biological and behavioral bases of naturally occurring maternal neglect, say UW-Madison zoology professor Stephen Gammie, who led the study, and co-author psychology professor Anthony Auger.

Good mouse mothers suckle, groom, and protect their pups, while their neglectful sisters may start out trying to care for a litter, but fail to follow through. "There seems to be a switch early on. The neglectful mice may nurse for a day or two after birth, but then the parental care ceases," Gammie says.

To separate the effects of genes and environment, the researchers set up a fostering study, in which pups born to previously nurturing mothers and previously neglectful mothers were switched immediately after birth.

Surprisingly, while nurturing moms attentively cared for foster pups born to other nurturing females, some became more neglectful when given foster pups born to a neglectful mother.

"In some cases the previously nurturing mothers would actively scatter the pups away from the nest, suggesting a negative cue from the pups or a lack of a positive cue," Gammie says. The result suggests that the offspring are somehow able to influence females' behavior and shows that maternal care can be affected by non-genetic factors.

In the fostering study, previously neglectful mothers did successfully raise some of the pups born to previously nurturing mothers, but these surviving pups showed lasting effects, including hyperactivity and low adult body weight. Some females neglected as youngsters were also poor mothers as adults, suggesting some aspects of neglect can be transmitted across generations.

The group also found evidence of genetic factors contributing to neglect. For example, virgin females that exhibited poor self-grooming and hyperactive behavior were at greater risk for becoming neglectful mothers.

To identify possible biological differences, the researchers analyzed brains of neglectful and nurturing mothers shortly after birth. In several brain regions - including some implicated in both maternal behaviors and reward responsiveness - they found higher levels of activity as well as signs of abnormal dopamine signaling in the neglectful mothers.

These patterns suggest that naturally occurring maternal neglect in these mice reflects disrupted reward-seeking behavior, Gammie says. In other words, these females may have the physical capability to take care of their pups, but may lack the proper motivation.

"It's been shown in a number of studies that parental care is a motivated, reward-related behavior," he says. "And it has been suggested by others that some aspects of child neglect in humans could result from a lack of reward of an offspring to the parent."

Though often overshadowed by more visible abuse cases, human child neglect may actually be a more widespread problem. A report published last week by the Centers for Disease Control and Prevention on U.S. children found that, among infants less than a week old, nearly 70 percent of nonfatal mistreatment cases from 2005 to 2006 were instances of neglect.

Child neglect has devastating consequences, Auger says, and the natural occurrence of maternal neglect within this mouse strain offers a powerful opportunity to investigate the biological and behavioral bases of maternal neglect.

Though he cautions that it's too early to know how their findings will translate to humans, for the mice "the difference is quite dramatic in the brain. Dopamine is likely not the only thing being disrupted, but it is an important starting signaling pathway to pursue."

Next, Auger says, "We hope to understand in greater detail the basis of naturally occurring neglect and provide treatment paradigms to these animals to restore natural maternal care of offspring."

Source: University of Wisconsin-Madison

Culture Can Change our Genes

Physician and social scientist, Harvard

I work in a borderland between social science and medicine, and I
therefore often find myself trying to reconcile conflicting facts and
perspectives about human biology and behavior. There are fellow
travelers at this border, of course, heading in both directions, or
just dawdling, but the border is both sparsely populated and
chaotic. The border is also, strangely, well patrolled, and it is
often quite hard to get authorities on both sides to coordinate
activities. Once in a while, however, I find that my passport (never
quite in order, according to officials) has acquired a new visa. For
me, this past year, I acquired the conviction that human evolution
may proceed much faster than I had thought, and that humans
themselves may be responsible.

In short, I have changed my mind about how people come literally to
embody the social world around them. I once thought that we
internalized cultural factors by forming memories, acquiring
language, or bearing emotional and physical marks (of poverty, of
conquest). I thought that this was the limit of the ways in which
our bodies were shaped by our social environment. In particular, I
thought that our genes were historically immutable, and that it was
not possible to imagine a conversation between culture and genetics.
I thought that we as a species evolved over time frames far too long
to be influenced by human actions.

I now think this is wrong, and that the alternative — that we are
evolving in real time, under the pressure of discernable social and
historical forces — is true. Rather than a monologue of genetics, or
a soliloquy of culture, there is a dialectic between genetics and

Evidence has been mounting for a decade. The best example so far is
the evolution of lactose tolerance in adults. The ability of adults
to digest lactose (a sugar in milk) confers evolutionary advantages
only when a stable supply of milk is available, such as after milk-
producing animals (sheep, cattle, goats) have been domesticated. The
advantages are several, ranging from a source of valuable calories to
a source of necessary hydration during times of water shortage or
spoilage. Amazingly, just over the last 3-9 thousand years, there
have been several adaptive mutations in widely separated populations
in Africa and Europe, all conferring the ability to digest lactose
(as shown by Sarah Tishkoff and others). These mutations are
principally seen in populations who are herders, and not in nearby
populations who have retained a hunter/gatherer lifestyle. This trait
is sufficiently advantageous that those with the trait have notably
many more descendants than those without.

A similar story can be told about mutations that have arisen in the
relatively recent historical past that confer advantages in terms of
surviving epidemic diseases such as typhoid. Since these diseases
were made more likely when the density of human settlements increased
and far-flung trade became possible, here we have another example of
how culture may affect our genes.

But this past year, a paper by John Hawks and colleagues in PNAS
functioned like the staccato plunk of a customs agent stamping my
documents and waving me on. The paper showed that the human genome
may be changing at an accelerating rate over the past 80,000 years,
and that this change may be in response not only to population growth
and adaptation to new environments, but also to cultural developments
that have made it possible for humans to sustain such population
growth or survive in such environments.

Our biology and our culture have always been in conversation of
course — just not (I had thought) on the genetic level. For example,
rising socio-economic status with industrial development results in
people becoming taller (a biological effect of a cultural
development) and taller people require architecture to change (a
cultural effect of a biological development). Anyone marveling at
the small size of beds in colonial-era houses knows this firsthand.
Similarly, an epidemic may induce large-scale social changes,
modifying kinship systems or political power. But genetic change
over short time periods? Yes.

Why does this matter? Because it is hard to know where this would
stop. There may be genetic variants that favor survival in cities,
that favor saving for retirement, that favor consumption of alcohol,
or that favor a preference for complicated social networks. There
may be genetic variants (based on altruistic genes that are a part of
our hominid heritage) that favor living in a democratic society,
others that favor living among computers, still others that favor
certain kinds of visual perception (maybe we are all more myopic as a
result of Medieval lens grinders). Modern cultural forms may favor
some traits over others. Maybe even the more complex world we live
in nowadays really is making us smarter.

This has been very difficult for me to accept because, unfortunately,
this also means that it may be the case that particular ways of
living create advantages for some, but not all, members of our
species. Certain groups may acquire (admittedly, over centuries)
certain advantages, and there might be positive or negative feedback
loops between genetics and culture. Maybe some of us really are
better able to cope with modernity than others. The idea that what
we choose to do with our world modifies what kind of offspring we
have is as amazing as it is troubling.