28 March 2012

Orchid Children

David Dobbs has a nice article at Wired on gene x enviromental interactions in the context of the orchid and dandeloin children hypothesis.

In a nutshell, this hypothesis re-evaluates what genes like "DRD4 [a dopamine processing gene] . . . the serotonin transporter gene (also known as SERT or 5HTTLPR), the short variant of which is often blamed for depression and anxiety disorders, and a variant of MAOA, the monoamine oxidase A gene, that some studies associated with aggression or violence." The hypothesis argues that rather than being genes that per se reflect negative behaviors, they actually reflect sensitivity to parenting quality.

This revisionist hypothesis is known variously as the sensitivity hypothesis, the differential susceptibility hypothesis, or the orchid-dandelion hypothesis — a term that Thomas Boyce and Bruce Ellis coined based on the vernacular Swedish term “dandelion children,” who seem to grow up okay in almost any environment; to that they added “orchid children,” who thrive under good care but wilt under bad.

Dobbs cites a 2010 study by Jay Belsky and Kevin Beaver that looked at both parenting quality and genotype that support this interpretation. The self-control and self-regulation of children with none of the variants, and of girls, was indifferent to parenting style. But, the more variants of these genes that a boy had, the more their self-control varied with parenting style. Boys with lots of these variants and "good parents" had above average self-control, while boys with few of these variants and "bad parents" had below average self-control.

The case that these genes have some positive function is supported by indications that they have been fitness enhancing targets of natural selection in humans:

These variants, Belsky and others note, appear to have emerged and then rapidly expanded through humankind over the last 50,000 to 100,000 years. Of the leading orchid-gene variants — the short SERT, the 7R DRD4, the more plastic version of the MAOA gene — none existed in humans 80,000 years ago. But since emerging through mutation (or, possibly, through interbreeding with other hominids), they have spread into 20 to 35% of the population.

“That’s not random drift,” says evolutionary anthropologist John Hawks. “They’re being selected for.”

Of course, it doesn't necessarily follow that just because genes were fitness enhancing in the Upper Paleolithic era that they are fitness enhancing in a modern technological 21st century society.

This research also suggests candidates for genes that might influence personality more generally, and just how subtle those genetic connections might be when environment also has to be factored into consideration. Many personality models treat self-control or something like it as a simple personality trait caused by genes, but in an Orchid Children Hypothesis, an effort to link the genes that actually seem to be involved with the self-control personality type will not see a genetic association, even though there is a complex but important one that appears to be involved.

A sensitivity model also doesn't just come into play in the personality trait of self-control. For example, one of the genetic traits hypothesized to be linked to pre-disposition to alcoholism basically comes down to a physiological trait that influences how easily you get drunk. Easy drunks are not prone to be alcoholics, because they can get a buzz with just a little alcohol and the effect is so strong that they tend to avoid it. People who hold their liquor too well, in contrast, need to drink large amounts to get a buzz and are prone to get into the habit of regular heavy drinking as a result.

The practical implications of Orchid v. Dandelion genes in children as genotyping grows ever less expensive are quite straightforward for parents. Parents with dandelion kids can rest easy knowing that their own parenting mistakes won't have as much of an impact on their children's development. Parents with boys who are orchid children, in contrast, would be under immense pressure to consider what kind of parenting practices they employ. The Freudian psychology instinct to look at childhood experience and parenting as a source of adult behavior may simultaneously be wrong and right. For most people the connection may be almost entirely absent, but for a minority, the connection may be profound.

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