Dad's the Id, Mom's the Ego

Thank Dad for Drive - but Thank Mom for Brains...

Success in almost any field depends more on energy and drive than it does on intelligence. This explains why we have so many stupid leaders.

- Sloan Wilson

New York - Another blow to male self-esteem. Researchers say mothers alone may pass on the genes which determine a child's intellectual power, while fathers impart those genes controlling more instinctual, "primitive" mental functions. An article in this week's New Scientist magazine says studies in mice are revealing that "the mother's genes contribute more to the development of the 'thinking' or 'executive' centres of the brain, while paternal genes have a greater impact on the development of the 'emotional' limbic brain."

Ongoing research at England's Cambridge University is exploring what scientists call "imprinted" genes, and their role in reproduction and evolution. Imprinted genes differ from other genes in that their activation within the developing child depends upon the sex of the parent from which the gene came. "Some imprinted genes work only if they come from the mother," the New Scientist article explains. "The same gene is silenced if it is inherited via the sperm rather than the egg."

Cambridge scientists stumbled upon this fact in 1984, during research that sought to discover if mammals could grow into maturity when supplied with the genes of just one parent. But they found such "androgenetic (mouse) embryos died, because certain vital genes had been switched off by the (donor) father." Delving deeper into this phenomenon, researchers realised that certain genes controlling the development of the conscious, "higher" level of brain function - intelligence - are silenced in the paternal version, but operative in the maternal one. Conversely, genes controlling more primitive limbic function - emotions, and the drives to eat, copulate, and compete - are silenced in the mother's genes, but activated in the father's.

In another study, Cambridge researchers examined the brain development of mouse embryos, abnormally weighted with extra amounts of the genes of either one parent or the other. "As the embryos matured cells that carried only paternal genes accumulated in clusters scattered throughout the 'emotional' brain - the hypothalamus, the amygdala," New Scientist reports. In embryos with maternally supplied genetic material, "cells containing only maternal genes were absent from the emotional brain. Instead, they selectively accumulated in the brain's executive region (the seat of higher, cognitive intelligence)."

Of course mice and men do differ. "It is very important work, and very, very promising," says Wolf Reik, who is studying the "imprinting" phenomenon at the Babraham Institute, near Cambridge. However, he admits that, at this stage "everyone is a little bit lost as to what it really means." But some psychologists are already trumpeting the discoveries as vindication of Freudian theory. Christopher Badcock, author of PsychoDarwinism, believes paternal genes help build Freud's famous "id" - the instinctual, emotional, unconscious self-while the mother's genes are behind the more rational, conscious "ego". During development, "maternal and paternal genes compete for control of behaviour," Badcock writes, "culminating in a mind divided into two conflicting parts strikingly similar to Freud's ego and id."

Whatever the psychological implications, experts believe "imprint" genes (of which only three or four have been identified so far) may number in the hundreds or thousands. Improperly switched on or off, they could also be the cause of numerous genetically inherited diseases. Researchers say more research may lead to ways of controlling the expression of such genes - and reversing the progress of these conditions.

Source: Reuters Friday 26 May 1998 from New Scientist 3 May 1997 pages 34 - 39

If you came directly to this page, you may wish to press the "Back" button below to read the Nature article "Mother and Father in Surprising Genetic Agreement" on the previous page as its topic is very similar.

For Motherly X Chromosome, Gender Is Only the Beginning

by Natalie Angier

As May dawns and the mothers among us excitedly anticipate the clever e-cards that we soon will be linking to and the overpriced brunches that we will somehow end up paying for, the following job description may ring a familiar note:

Must be exceptionally stable yet ridiculously responsive to the needs of those around you; must be willing to trail after your loved ones, cleaning up their messes and compensating for their deficiencies and selfishness; must work twice as hard as everybody else; must accept blame for a long list of the world’s illnesses; must have a knack for shaping young minds while in no way neglecting the less glamorous tissues below; must have a high tolerance for babble and repetition; and must agree, when asked, to shut up, fade into the background and pretend you don’t exist.

As it happens, the above precis refers not only to the noble profession of motherhood to which we all owe our lives and guilt complexes. It is also a decent character sketch of the chromosome that allows a human or any other mammal to become a mother in the first place: the X chromosome.

The X chromosome, like its shorter, stubbier but no less conspicuous counterpart, the Y chromosome, is a so-called sex chromosome, a segment of DNA entrusted with the pivotal task of sex determination. A mammalian embryo outfitted with an X and Y chromosomal set buds into a male, while a mammal bearing a pair of X chromosomes emerges from the maternal berth with birthing options of her own.

Yet the X chromosome does much more than help specify an animal’s reproductive plumbing. As scientists who study the chromosome lately have learned, the X is a rich repository of genes vital to brain development and could hold the key to the evolution of our particularly corrugated cortex. Moreover, the X chromosome behaves unlike any of the other chromosomes of the body - unlike little big-man Y, certainly, but also unlike our 22 other pairs of chromosomes, the self-satisfied autosomes that constitute the rest of our genome, of the complete DNA kit packed into every cell that we carry. It is a supple, switchbacking, multitasking gumby doll patch of the genome; and the closer you look, the more Cirque du Soleil it appears.

Although the precise details of its chemical structure and performance are only just emerging, the X chromosome has long been renowned among geneticists, who named it X not because of its shape, as is commonly presumed - the non-sex chromosomes also vaguely resemble an "X" at times during cell division - but because they were baffled by the way it held itself apart from the other chromosomal pairs. "They called it X for unknown," said Mark T Ross of the X Chromosome Group at the Wellcome Trust Sanger Institute in Cambridge. (When its much tinier male counterpart was finally detected, researchers simply continued down the alphabet for a name.) Many of the diseases first understood to be hereditary were linked to X’s span, for the paradoxical reason that such conditions showed their face most often in those with just a single X to claim: men.

Scientists eventually determined that we inherit two copies of our 23,000 or so genes, one from each parent; and that these genes, these chemical guidelines for how to build and maintain a human, are scattered among the 23 pairs of chromosomes, along with unseemly amounts of apparent chemical babble.

Having two copies of every gene proves especially handy when one of those paired genes is defective, at which point the working version of the gene can step in and specify enough of the essential bodybuilding protein that the baby blooms just fine and may never know its DNA is hemi-flawed. And here is where the Y’s petite stature looms large. Because it holds a mere 50ish different genes against its counterpart’s 1,100, the vast majority of X-based genes have no potential pinch-hitter on the Y. A boy who inherits from his mother an X chromosome that enfolds a faulty gene for a bloodclotting factor, say, or for a muscle protein or for a color receptor won’t find succor in the chromosomal analogue bestowed by Dad. He will be born with hemophilia, or muscular dystrophy, or color-blindness. But, hey, he will be a boy, for male-making is the task to which the Y chromosome is almost exclusively devoted.

In fact, it is to compensate for the monomania of the Y that the X chromosome has become such a mother of a multitasker. Over the 300 million years of evolution, as the Y chromosome has shrugged off more of its generic genetic responsibilities in pursuit of sexual specialization, the X has had to pick up the slack. It, too, has pawned off genes to other chromosomes. But for those genes still in its charge, the X must double their output, to prod each gene to spool out twice the protein of an ordinary gene and thus be the solo equivalent of any twinned genes located on other, nonsexy chromosomes.

Ah, but women, who have two X chromosomes, two copies of those 1,100 genes: What of them? With its usual Seussian sense of playfulness, evolution has opted to zeedo the hoofenanny. In a girl’s cells, you don’t see two pleasantly active X chromosomes behaving like two ordinary nonsex chromosomes. You see one hyperactive X chromosome, its genes busily pumping out twice the standard issue of protein, just as in a boy’s cells; and you see one X chromosome that has been largely though not wholly shut down, said Laura Carrel, a geneticist at Penn State College of Medicine.

Through an elaborate process called X inactivation, the chromosome is blanketed with a duct tape of nucleic acid. In some cells of a woman’s body it may be the chromosome from Dad that’s muffled, while in other cells the maternal one stays mum. Every daughter, then, is a walking mosaic of clamorous and quiet chromosomes, of fatherly sermons and maternal advice, while every son has but his mother’s voice to guide him. Remember this, fellows: you are all mama’s boys.

Source: nytimes.com 1 May 2007

IQ Is Inherited, Suggests Twin Study

by Alison Motluk

Genes have a very strong influence over how certain parts of our brains develop, scientists in the US and Finland have found. And the parts most influenced are those that govern our cognitive ability. In short, you inherit your IQ.

Paul Thompson at the University of California at Los Angeles and his colleagues used MRI to scan the brains of 10 pairs of identical and 10 pairs of fraternal twins. Identical twins have identical genes, whereas fraternal twins sharing on average half their genes. The twins shared environments, means researchers can separate genetic and environmental factors. The researchers found that certain regions of the brain were highly heritable. These included language areas, known as Broca's and Wernicke's areas, and the frontal region, which, among other things, plays a huge role in cognition.

In identical twins, these areas showed a 95 to 100% correlation between one twin and the other - they were essentially the same. The frontal structure, says Thompson, appears to be as highly influenced by genes as the most highly influenced trait we know of - fingerprints. "It's extraordinary how similar they are," he says. The finding suggests that environment - their experiences, what they learned in life, who they knew - played a negligible role in shaping it.

Fraternal twins were near-identical in Wernicke's area, but less similar in other areas, with about 60 to 70% correlation. Random pairs of people would be expected to have no correlation.

Intellectual function

The study was all the more interesting in that it found that not only was this gray matter highly heritable, but it affected overall intelligence as well. "We found that differences in frontal gray matter were significantly linked with differences in intellectual function," the authors write.

The volunteers each took a battery of tests that examined 17 separate abilities, including verbal and spatial working memory, attention tasks, verbal knowledge, motor speed and visuospatial ability. These tests hone in on what's known as "g", the common element measured by IQ tests. People who do well on one of these tests tend to do well on them all, says Thompson.

It is not known what exactly "g" is. But these new findings suggest that "g" is not just a statistical abstraction, but rather, that it has a biological substrate in the brain, says Robert Plomin, of the Institute of Psychiatry in London. Plomin has spent eight years looking for genes behind "g". "I'm convinced that there are genes," he says, a lot of them, each with a small effect.

Stephen Kosslyn of Harvard University in Boston questions whether "g" should really be called intelligence. "G" picks up on abilities such as being able to abstract rules or figure out how to order things according to rules. "It's the kind of intelligence you need to do well in school," he says. "Not what you need to do well in life."

Journal reference: Nature Neuroscience (DOI: 10.1038/nn758)

Source: newscientist.com 5 November 2001

Stephen Kosslyn appears to be good at abstracting rules and at figuring out how to order things according to rules. Do you suppose that means he hasn't done well in life? Or is that a faulty syllogism? Can you have a high IQ and also have those characteristics you need to "do well in life"? This article doesn't address that issue. If you can't have both, then can we safely assume that all wealthy people are stupid?

Moms' Poor Vocabulary Hurts Kids' Future

by Karen S Peterson

Mothers should "teach letters to their babies, talk out loud to them and read books to them regularly and consistently.
This is much less likely to happen when the mother is trapped on the bottom rungs of the socioeconomic ladder."

- Study co-author George Farkas

If a child comes from an economically deprived home with a mom who has a poor vocabulary, by the age of 3 his fate just may be sealed: he will possibly never catch up in school and have lifelong struggles with learning, a new study shows.

"Those children in our society who grow up in poverty or near poverty are adversely affected by their mother's own vocabulary deficit during their earliest years, when they are learning to speak at home," says George Farkas, a Penn State sociologist and co-author of the study.

The vocabulary gap suffered by children emerges at the earliest ages in both disadvantaged black and white homes, he says, and becomes dramatic by 36 months, Farkas says.

The problem lessens once a child is in school and comes in contact with verbal teachers and others. "By the time the child is 6 and enters first grade, the vocabulary gap doesn't widen any further," Farkas says. After starting school, there is "an upward-looking growth curve" for the disadvantaged kids that remains parallel with those from more middle-class homes. But his research shows the economically deprived children never truly recover "from the damage done in the early, preschool years." Typically, such youngsters don't read as quickly or as well.

"The first-grade teacher usually is told to get students reading by Christmas," Farkas says. "If students come from low-income backgrounds, with a limited vocabulary and often non-standard English grammar and pronunciation, they are in a big predicament." Not only must Mom be reasonably verbal, Farkas finds, but she must instruct "in a sufficiently warm and attractive manner so that the lesson takes." It is, he says, "necessary for mothers to teach letters to their babies, talk out loud to them and read books to them regularly and consistently. This is much less likely to happen when the mother is trapped on the bottom rungs of the socioeconomic ladder and is consumed by financial and emotional pressures or stresses."

Farkas analysed a variety of findings from the National Longitudinal Survey of Youth Data, which is funded in part by the federal government. He analysed separately 3,500 white and 3,300 black children tracked periodically between ages 3 and 12, concentrating on socio-economic classes in each racial group. His findings, he says, show the need for government policies that will reach out to the youngest children in order to create "school-readiness skills."

Educators and child development specialists have long known about the significance of early vocabulary skills, says Ted Feinberg of the National Association of School Psychologists. "We know how critically important vocabulary is to all of the additional learning skills that are required of schoolchildren throughout their school careers," he says. "If they do not have a solid foundation in vocabulary, it does not surprise me that they continue to lag behind."

Source: USA Today 12 April 2001

I'm not sure Farkas' study clearly separates cause and effect. If the mothers had a great vocabulary and lots of unstressed time to talk to and play with their kids, they probably wouldn't be at the bottom of the socioeconomic ladder in the first place. A "good" vocabulary is a problematical term anyway - a child growing up in a black ghetto may in fact have a wide vocabulary, able to employ lots of words YOU may never have heard of. Besides, if IQ is inherited from the mother, if she is below average in her skills, is it that surprising her children might be as well?